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tree.c revision 1.457
      1 /*	$NetBSD: tree.c,v 1.457 2022/06/21 22:16:26 rillig Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1994, 1995 Jochen Pohl
      5  * All Rights Reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *      This product includes software developed by Jochen Pohl for
     18  *	The NetBSD Project.
     19  * 4. The name of the author may not be used to endorse or promote products
     20  *    derived from this software without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     32  */
     33 
     34 #if HAVE_NBTOOL_CONFIG_H
     35 #include "nbtool_config.h"
     36 #endif
     37 
     38 #include <sys/cdefs.h>
     39 #if defined(__RCSID)
     40 __RCSID("$NetBSD: tree.c,v 1.457 2022/06/21 22:16:26 rillig Exp $");
     41 #endif
     42 
     43 #include <float.h>
     44 #include <limits.h>
     45 #include <math.h>
     46 #include <signal.h>
     47 #include <stdlib.h>
     48 #include <string.h>
     49 
     50 #include "lint1.h"
     51 
     52 typedef struct integer_constraints {
     53 	int64_t		smin;	/* signed minimum */
     54 	int64_t		smax;	/* signed maximum */
     55 	uint64_t	umin;	/* unsigned minimum */
     56 	uint64_t	umax;	/* unsigned maximum */
     57 	uint64_t	bset;	/* bits that are definitely set */
     58 	uint64_t	bclr;	/* bits that are definitely clear */
     59 } integer_constraints;
     60 
     61 static	tnode_t	*build_integer_constant(tspec_t, int64_t);
     62 static	void	check_pointer_comparison(op_t,
     63 					 const tnode_t *, const tnode_t *);
     64 static	bool	check_assign_types_compatible(op_t, int,
     65 					      const tnode_t *, const tnode_t *);
     66 static	void	check_bad_enum_operation(op_t,
     67 					 const tnode_t *, const tnode_t *);
     68 static	void	check_enum_type_mismatch(op_t, int,
     69 				         const tnode_t *, const tnode_t *);
     70 static	void	check_enum_int_mismatch(op_t, int,
     71 					const tnode_t *, const tnode_t *);
     72 static	tnode_t	*new_tnode(op_t, bool, type_t *, tnode_t *, tnode_t *);
     73 static	void	balance(op_t, tnode_t **, tnode_t **);
     74 static	void	warn_incompatible_types(op_t, const type_t *, tspec_t,
     75 					const type_t *, tspec_t);
     76 static	void	warn_incompatible_pointers(const mod_t *,
     77 					   const type_t *, const type_t *);
     78 static	bool	has_constant_member(const type_t *);
     79 static	void	check_prototype_conversion(int, tspec_t, tspec_t, type_t *,
     80 					   tnode_t *);
     81 static	void	check_integer_conversion(op_t, int, tspec_t, tspec_t, type_t *,
     82 					 tnode_t *);
     83 static	void	check_pointer_integer_conversion(op_t, tspec_t, type_t *,
     84 						 tnode_t *);
     85 static	void	check_pointer_conversion(tnode_t *, type_t *);
     86 static	tnode_t	*build_struct_access(op_t, bool, tnode_t *, tnode_t *);
     87 static	tnode_t	*build_prepost_incdec(op_t, bool, tnode_t *);
     88 static	tnode_t	*build_real_imag(op_t, bool, tnode_t *);
     89 static	tnode_t	*build_address(bool, tnode_t *, bool);
     90 static	tnode_t	*build_plus_minus(op_t, bool, tnode_t *, tnode_t *);
     91 static	tnode_t	*build_bit_shift(op_t, bool, tnode_t *, tnode_t *);
     92 static	tnode_t	*build_colon(bool, tnode_t *, tnode_t *);
     93 static	tnode_t	*build_assignment(op_t, bool, tnode_t *, tnode_t *);
     94 static	tnode_t	*subt_size_in_bytes(type_t *);
     95 static	tnode_t	*fold(tnode_t *);
     96 static	tnode_t	*fold_bool(tnode_t *);
     97 static	tnode_t	*fold_float(tnode_t *);
     98 static	tnode_t	*check_function_arguments(type_t *, tnode_t *);
     99 static	tnode_t	*check_prototype_argument(int, type_t *, tnode_t *);
    100 static	void	check_null_effect(const tnode_t *);
    101 static	void	check_array_index(tnode_t *, bool);
    102 static	void	check_integer_comparison(op_t, tnode_t *, tnode_t *);
    103 static	void	check_precedence_confusion(tnode_t *);
    104 
    105 extern sig_atomic_t fpe;
    106 
    107 static bool
    108 ic_maybe_signed(const type_t *tp, const integer_constraints *ic)
    109 {
    110 
    111 	return !is_uinteger(tp->t_tspec) &&
    112 	    (ic->bclr & ((uint64_t)1 << 63)) == 0;
    113 }
    114 
    115 static unsigned
    116 ic_length_in_bits(const type_t *tp)
    117 {
    118 
    119 	lint_assert(is_integer(tp->t_tspec));
    120 	return tp->t_bitfield ? tp->t_flen : size_in_bits(tp->t_tspec);
    121 }
    122 
    123 static integer_constraints
    124 ic_any(const type_t *tp)
    125 {
    126 	integer_constraints c;
    127 
    128 	uint64_t vbits = value_bits(ic_length_in_bits(tp));
    129 	if (is_uinteger(tp->t_tspec)) {
    130 		c.smin = INT64_MIN;
    131 		c.smax = INT64_MAX;
    132 		c.umin = 0;
    133 		c.umax = vbits;
    134 		c.bset = 0;
    135 		c.bclr = ~c.umax;
    136 	} else {
    137 		c.smin = (int64_t)-1 - (int64_t)(vbits >> 1);
    138 		c.smax = (int64_t)(vbits >> 1);
    139 		c.umin = 0;
    140 		c.umax = UINT64_MAX;
    141 		c.bset = 0;
    142 		c.bclr = 0;
    143 	}
    144 	return c;
    145 }
    146 
    147 static integer_constraints
    148 ic_con(const type_t *tp, const val_t *v)
    149 {
    150 	integer_constraints c;
    151 
    152 	lint_assert(is_integer(tp->t_tspec));
    153 	int64_t s = v->v_quad;
    154 	uint64_t u = (uint64_t)s;
    155 	c.smin = s;
    156 	c.smax = s;
    157 	c.umin = u;
    158 	c.umax = u;
    159 	c.bset = u;
    160 	c.bclr = ~u;
    161 	return c;
    162 }
    163 
    164 static integer_constraints
    165 ic_cvt(const type_t *ntp, const type_t *otp, integer_constraints a)
    166 {
    167 
    168 	if (ic_length_in_bits(ntp) > ic_length_in_bits(otp) &&
    169 	    is_uinteger(otp->t_tspec))
    170 		return a;
    171 	return ic_any(ntp);
    172 }
    173 
    174 static integer_constraints
    175 ic_bitand(integer_constraints a, integer_constraints b)
    176 {
    177 	integer_constraints c;
    178 
    179 	c.smin = INT64_MIN;
    180 	c.smax = INT64_MAX;
    181 	c.umin = 0;
    182 	c.umax = UINT64_MAX;
    183 	c.bset = a.bset & b.bset;
    184 	c.bclr = a.bclr | b.bclr;
    185 	return c;
    186 }
    187 
    188 static integer_constraints
    189 ic_bitor(integer_constraints a, integer_constraints b)
    190 {
    191 	integer_constraints c;
    192 
    193 	c.smin = INT64_MIN;
    194 	c.smax = INT64_MAX;
    195 	c.umin = 0;
    196 	c.umax = UINT64_MAX;
    197 	c.bset = a.bset | b.bset;
    198 	c.bclr = a.bclr & b.bclr;
    199 	return c;
    200 }
    201 
    202 static integer_constraints
    203 ic_shl(const type_t *tp, integer_constraints a, integer_constraints b)
    204 {
    205 	integer_constraints c;
    206 	unsigned int amount;
    207 
    208 	if (ic_maybe_signed(tp, &a))
    209 		return ic_any(tp);
    210 
    211 	if (b.smin == b.smax && b.smin >= 0 && b.smin < 64)
    212 		amount = (unsigned int)b.smin;
    213 	else if (b.umin == b.umax && b.umin < 64)
    214 		amount = (unsigned int)b.umin;
    215 	else
    216 		return ic_any(tp);
    217 
    218 	c.smin = INT64_MIN;
    219 	c.smax = INT64_MAX;
    220 	c.umin = 0;
    221 	c.umax = UINT64_MAX;
    222 	c.bset = a.bset << amount;
    223 	c.bclr = a.bclr << amount | (((uint64_t)1 << amount) - 1);
    224 	return c;
    225 }
    226 
    227 static integer_constraints
    228 ic_shr(const type_t *tp, integer_constraints a, integer_constraints b)
    229 {
    230 	integer_constraints c;
    231 	unsigned int amount;
    232 
    233 	if (ic_maybe_signed(tp, &a))
    234 		return ic_any(tp);
    235 
    236 	if (b.smin == b.smax && b.smin >= 0 && b.smin < 64)
    237 		amount = (unsigned int)b.smin;
    238 	else if (b.umin == b.umax && b.umin < 64)
    239 		amount = (unsigned int)b.umin;
    240 	else
    241 		return ic_any(tp);
    242 
    243 	c.smin = INT64_MIN;
    244 	c.smax = INT64_MAX;
    245 	c.umin = 0;
    246 	c.umax = UINT64_MAX;
    247 	c.bset = a.bset >> amount;
    248 	c.bclr = a.bclr >> amount | ~(~(uint64_t)0 >> amount);
    249 	return c;
    250 }
    251 
    252 static integer_constraints
    253 ic_expr(const tnode_t *tn)
    254 {
    255 	integer_constraints lc, rc;
    256 
    257 	lint_assert(is_integer(tn->tn_type->t_tspec));
    258 
    259 	switch (tn->tn_op) {
    260 	case CON:
    261 		return ic_con(tn->tn_type, tn->tn_val);
    262 	case CVT:
    263 		if (!is_integer(tn->tn_left->tn_type->t_tspec))
    264 			return ic_any(tn->tn_type);
    265 		lc = ic_expr(tn->tn_left);
    266 		return ic_cvt(tn->tn_type, tn->tn_left->tn_type, lc);
    267 	case SHL:
    268 		lc = ic_expr(tn->tn_left);
    269 		rc = ic_expr(tn->tn_right);
    270 		return ic_shl(tn->tn_type, lc, rc);
    271 	case SHR:
    272 		lc = ic_expr(tn->tn_left);
    273 		rc = ic_expr(tn->tn_right);
    274 		return ic_shr(tn->tn_type, lc, rc);
    275 	case BITAND:
    276 		lc = ic_expr(tn->tn_left);
    277 		rc = ic_expr(tn->tn_right);
    278 		return ic_bitand(lc, rc);
    279 	case BITOR:
    280 		lc = ic_expr(tn->tn_left);
    281 		rc = ic_expr(tn->tn_right);
    282 		return ic_bitor(lc, rc);
    283 	default:
    284 		return ic_any(tn->tn_type);
    285 	}
    286 }
    287 
    288 static const char *
    289 op_name(op_t op)
    290 {
    291 	return modtab[op].m_name;
    292 }
    293 
    294 /* Build 'pointer to tp', 'array of tp' or 'function returning tp'. */
    295 type_t *
    296 block_derive_type(type_t *tp, tspec_t t)
    297 {
    298 	type_t	*tp2;
    299 
    300 	tp2 = block_zero_alloc(sizeof(*tp2));
    301 	tp2->t_tspec = t;
    302 	tp2->t_subt = tp;
    303 	return tp2;
    304 }
    305 
    306 /*
    307  * Derive 'pointer to tp' or 'function returning tp'.
    308  * The memory is freed at the end of the current expression.
    309  */
    310 type_t *
    311 expr_derive_type(type_t *tp, tspec_t t)
    312 {
    313 	type_t	*tp2;
    314 
    315 	tp2 = expr_zero_alloc(sizeof(*tp2));
    316 	tp2->t_tspec = t;
    317 	tp2->t_subt = tp;
    318 	return tp2;
    319 }
    320 
    321 /*
    322  * Create a node for a constant.
    323  */
    324 tnode_t *
    325 build_constant(type_t *tp, val_t *v)
    326 {
    327 	tnode_t	*n;
    328 
    329 	n = expr_alloc_tnode();
    330 	n->tn_op = CON;
    331 	n->tn_type = tp;
    332 	n->tn_val = expr_zero_alloc(sizeof(*n->tn_val));
    333 	n->tn_val->v_tspec = tp->t_tspec;
    334 	n->tn_val->v_unsigned_since_c90 = v->v_unsigned_since_c90;
    335 	n->tn_val->v_u = v->v_u;
    336 	free(v);
    337 	return n;
    338 }
    339 
    340 static tnode_t *
    341 build_integer_constant(tspec_t t, int64_t q)
    342 {
    343 	tnode_t	*n;
    344 
    345 	n = expr_alloc_tnode();
    346 	n->tn_op = CON;
    347 	n->tn_type = gettyp(t);
    348 	n->tn_val = expr_zero_alloc(sizeof(*n->tn_val));
    349 	n->tn_val->v_tspec = t;
    350 	n->tn_val->v_quad = q;
    351 	return n;
    352 }
    353 
    354 static void
    355 fallback_symbol(sym_t *sym)
    356 {
    357 
    358 	if (fallback_symbol_strict_bool(sym))
    359 		return;
    360 
    361 	if (block_level > 0 && (strcmp(sym->s_name, "__FUNCTION__") == 0 ||
    362 			   strcmp(sym->s_name, "__PRETTY_FUNCTION__") == 0)) {
    363 		/* __FUNCTION__/__PRETTY_FUNCTION__ is a GCC extension */
    364 		gnuism(316);
    365 		sym->s_type = block_derive_type(gettyp(CHAR), PTR);
    366 		sym->s_type->t_const = true;
    367 		return;
    368 	}
    369 
    370 	if (block_level > 0 && strcmp(sym->s_name, "__func__") == 0) {
    371 		if (!allow_c99)
    372 			/* __func__ is a C99 feature */
    373 			warning(317);
    374 		sym->s_type = block_derive_type(gettyp(CHAR), PTR);
    375 		sym->s_type->t_const = true;
    376 		return;
    377 	}
    378 
    379 	/* '%s' undefined */
    380 	error(99, sym->s_name);
    381 }
    382 
    383 /*
    384  * Functions that are predeclared by GCC or other compilers can be called
    385  * with arbitrary arguments.  Since lint usually runs after a successful
    386  * compilation, it's the compiler's job to catch any errors.
    387  */
    388 bool
    389 is_compiler_builtin(const char *name)
    390 {
    391 	/* https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html */
    392 	if (allow_gcc) {
    393 		if (strncmp(name, "__atomic_", 9) == 0 ||
    394 		    strncmp(name, "__builtin_", 10) == 0 ||
    395 		    strcmp(name, "alloca") == 0 ||
    396 		    /* obsolete but still in use, as of 2021 */
    397 		    strncmp(name, "__sync_", 7) == 0)
    398 			return true;
    399 	}
    400 
    401 	/* https://software.intel.com/sites/landingpage/IntrinsicsGuide/ */
    402 	if (strncmp(name, "_mm_", 4) == 0)
    403 		return true;
    404 
    405 	return false;
    406 }
    407 
    408 static bool
    409 str_endswith(const char *haystack, const char *needle)
    410 {
    411 	size_t hlen = strlen(haystack);
    412 	size_t nlen = strlen(needle);
    413 
    414 	return nlen <= hlen &&
    415 	       memcmp(haystack + hlen - nlen, needle, nlen) == 0;
    416 }
    417 
    418 /* https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html */
    419 static bool
    420 is_gcc_bool_builtin(const char *name)
    421 {
    422 	return strncmp(name, "__builtin_", 10) == 0 &&
    423 	       (str_endswith(name, "_overflow") ||
    424 		str_endswith(name, "_overflow_p"));
    425 }
    426 
    427 static void
    428 build_name_call(sym_t *sym)
    429 {
    430 
    431 	if (is_compiler_builtin(sym->s_name)) {
    432 		/*
    433 		 * Do not warn about these, just assume that
    434 		 * they are regular functions compatible with
    435 		 * non-prototype calling conventions.
    436 		 */
    437 		if (allow_gcc && is_gcc_bool_builtin(sym->s_name))
    438 			sym->s_type = gettyp(BOOL);
    439 
    440 	} else if (allow_c99) {
    441 		/* function '%s' implicitly declared to return int */
    442 		error(215, sym->s_name);
    443 	} else if (!allow_trad) {
    444 		/* function '%s' implicitly declared to return int */
    445 		warning(215, sym->s_name);
    446 	}
    447 
    448 	/* XXX if !allow_c90, the symbol should be exported to level 0 */
    449 	sym->s_type = block_derive_type(sym->s_type, FUNC);
    450 }
    451 
    452 /* Create a node for a name (symbol table entry). */
    453 tnode_t *
    454 build_name(sym_t *sym, bool is_funcname)
    455 {
    456 	tnode_t	*n;
    457 
    458 	if (sym->s_scl == NOSCL) {
    459 		sym->s_scl = EXTERN;
    460 		sym->s_def = DECL;
    461 		if (is_funcname)
    462 			build_name_call(sym);
    463 		else
    464 			fallback_symbol(sym);
    465 	}
    466 
    467 	lint_assert(sym->s_kind == FVFT || sym->s_kind == FMEMBER);
    468 
    469 	n = expr_alloc_tnode();
    470 	n->tn_type = sym->s_type;
    471 	if (sym->s_scl == BOOL_CONST) {
    472 		n->tn_op = CON;
    473 		n->tn_val = expr_zero_alloc(sizeof(*n->tn_val));
    474 		n->tn_val->v_tspec = BOOL;
    475 		n->tn_val->v_quad = sym->u.s_bool_constant ? 1 : 0;
    476 	} else if (sym->s_scl == ENUM_CONST) {
    477 		n->tn_op = CON;
    478 		n->tn_val = expr_zero_alloc(sizeof(*n->tn_val));
    479 		n->tn_val->v_tspec = INT;	/* ENUM is in n->tn_type */
    480 		n->tn_val->v_quad = sym->u.s_enum_constant;
    481 	} else {
    482 		n->tn_op = NAME;
    483 		n->tn_sym = sym;
    484 		if (sym->s_kind == FVFT && sym->s_type->t_tspec != FUNC)
    485 			n->tn_lvalue = true;
    486 	}
    487 
    488 	return n;
    489 }
    490 
    491 tnode_t *
    492 build_string(strg_t *strg)
    493 {
    494 	size_t	len;
    495 	tnode_t	*n;
    496 	type_t *tp;
    497 
    498 	len = strg->st_len;
    499 
    500 	n = expr_alloc_tnode();
    501 
    502 	tp = expr_zero_alloc(sizeof(*tp));
    503 	tp->t_tspec = ARRAY;
    504 	tp->t_subt = gettyp(strg->st_char ? CHAR : WCHAR);
    505 	tp->t_dim = (int)(len + 1);
    506 
    507 	n->tn_op = STRING;
    508 	n->tn_type = tp;
    509 	n->tn_lvalue = true;
    510 
    511 	n->tn_string = expr_zero_alloc(sizeof(*n->tn_string));
    512 	n->tn_string->st_char = strg->st_char;
    513 	n->tn_string->st_len = len;
    514 
    515 	size_t chsize = strg->st_char ? sizeof(char) : sizeof(wchar_t);
    516 	size_t size = (len + 1) * chsize;
    517 	n->tn_string->st_mem = expr_zero_alloc(size);
    518 	(void)memcpy(n->tn_string->st_mem, strg->st_mem, size);
    519 	free(strg->st_mem);
    520 	free(strg);
    521 
    522 	return n;
    523 }
    524 
    525 /*
    526  * Returns a symbol which has the same name as the msym argument and is a
    527  * member of the struct or union specified by the tn argument.
    528  */
    529 static sym_t *
    530 struct_or_union_member(tnode_t *tn, op_t op, sym_t *msym)
    531 {
    532 	struct_or_union	*str;
    533 	type_t	*tp;
    534 	sym_t	*sym, *csym;
    535 	bool	eq;
    536 	tspec_t	t;
    537 
    538 	/*
    539 	 * Remove the member if it was unknown until now, which means
    540 	 * that no defined struct or union has a member with the same name.
    541 	 */
    542 	if (msym->s_scl == NOSCL) {
    543 		/* type '%s' does not have member '%s' */
    544 		error(101, type_name(tn->tn_type), msym->s_name);
    545 		rmsym(msym);
    546 		msym->s_kind = FMEMBER;
    547 		msym->s_scl = MOS;
    548 
    549 		struct_or_union *sou = expr_zero_alloc(sizeof(*sou));
    550 		sou->sou_tag = expr_zero_alloc(sizeof(*sou->sou_tag));
    551 		sou->sou_tag->s_name = unnamed;
    552 
    553 		msym->u.s_member.sm_sou_type = sou;
    554 		/*
    555 		 * The member sm_offset_in_bits is not needed here since this
    556 		 * symbol can only be used for error reporting.
    557 		 */
    558 		return msym;
    559 	}
    560 
    561 	/* Set str to the tag of which msym is expected to be a member. */
    562 	str = NULL;
    563 	t = (tp = tn->tn_type)->t_tspec;
    564 	if (op == POINT) {
    565 		if (is_struct_or_union(t))
    566 			str = tp->t_str;
    567 	} else if (op == ARROW && t == PTR) {
    568 		t = (tp = tp->t_subt)->t_tspec;
    569 		if (is_struct_or_union(t))
    570 			str = tp->t_str;
    571 	}
    572 
    573 	/*
    574 	 * If this struct/union has a member with the name of msym, return it.
    575 	 */
    576 	if (str != NULL) {
    577 		for (sym = msym; sym != NULL; sym = sym->s_symtab_next) {
    578 			if (!is_member(sym))
    579 				continue;
    580 			if (sym->u.s_member.sm_sou_type != str)
    581 				continue;
    582 			if (strcmp(sym->s_name, msym->s_name) != 0)
    583 				continue;
    584 			return sym;
    585 		}
    586 	}
    587 
    588 	/*
    589 	 * Set eq to false if there are struct/union members with the same
    590 	 * name and different types and/or offsets.
    591 	 */
    592 	eq = true;
    593 	for (csym = msym; csym != NULL; csym = csym->s_symtab_next) {
    594 		if (csym->s_scl != MOS && csym->s_scl != MOU)
    595 			continue;
    596 		if (strcmp(msym->s_name, csym->s_name) != 0)
    597 			continue;
    598 		for (sym = csym->s_symtab_next; sym != NULL;
    599 		    sym = sym->s_symtab_next) {
    600 			bool w;
    601 
    602 			if (sym->s_scl != MOS && sym->s_scl != MOU)
    603 				continue;
    604 			if (strcmp(csym->s_name, sym->s_name) != 0)
    605 				continue;
    606 			if (csym->u.s_member.sm_offset_in_bits !=
    607 			    sym->u.s_member.sm_offset_in_bits) {
    608 				eq = false;
    609 				break;
    610 			}
    611 			w = false;
    612 			eq = eqtype(csym->s_type, sym->s_type,
    613 			    false, false, &w) && !w;
    614 			if (!eq)
    615 				break;
    616 			if (csym->s_bitfield != sym->s_bitfield) {
    617 				eq = false;
    618 				break;
    619 			}
    620 			if (csym->s_bitfield) {
    621 				type_t	*tp1, *tp2;
    622 
    623 				tp1 = csym->s_type;
    624 				tp2 = sym->s_type;
    625 				if (tp1->t_flen != tp2->t_flen) {
    626 					eq = false;
    627 					break;
    628 				}
    629 				if (tp1->t_foffs != tp2->t_foffs) {
    630 					eq = false;
    631 					break;
    632 				}
    633 			}
    634 		}
    635 		if (!eq)
    636 			break;
    637 	}
    638 
    639 	/*
    640 	 * Now handle the case in which the left operand refers really
    641 	 * to a struct/union, but the right operand is not member of it.
    642 	 */
    643 	if (str != NULL) {
    644 		if (eq && !allow_c90) {
    645 			/* illegal use of member '%s' */
    646 			warning(102, msym->s_name);
    647 		} else {
    648 			/* illegal use of member '%s' */
    649 			error(102, msym->s_name);
    650 		}
    651 		return msym;
    652 	}
    653 
    654 	/*
    655 	 * Now the left operand of ARROW does not point to a struct/union
    656 	 * or the left operand of POINT is no struct/union.
    657 	 */
    658 	if (eq) {
    659 		if (op == POINT) {
    660 			if (!allow_c90) {
    661 				/* left operand of '.' must be struct ... */
    662 				warning(103, type_name(tn->tn_type));
    663 			} else {
    664 				/* left operand of '.' must be struct ... */
    665 				error(103, type_name(tn->tn_type));
    666 			}
    667 		} else {
    668 			if (!allow_c90 && tn->tn_type->t_tspec == PTR) {
    669 				/* left operand of '->' must be pointer ... */
    670 				warning(104, type_name(tn->tn_type));
    671 			} else {
    672 				/* left operand of '->' must be pointer ... */
    673 				error(104, type_name(tn->tn_type));
    674 			}
    675 		}
    676 	} else {
    677 		if (!allow_c90) {
    678 			/* non-unique member requires struct/union %s */
    679 			error(105, op == POINT ? "object" : "pointer");
    680 		} else {
    681 			/* unacceptable operand of '%s' */
    682 			error(111, op_name(op));
    683 		}
    684 	}
    685 
    686 	return msym;
    687 }
    688 
    689 tnode_t *
    690 build_generic_selection(const tnode_t *expr,
    691 			struct generic_association *sel)
    692 {
    693 	tnode_t *default_result = NULL;
    694 
    695 	for (; sel != NULL; sel = sel->ga_prev) {
    696 		if (expr != NULL &&
    697 		    eqtype(sel->ga_arg, expr->tn_type, false, false, NULL))
    698 			return sel->ga_result;
    699 		else if (sel->ga_arg == NULL)
    700 			default_result = sel->ga_result;
    701 	}
    702 	return default_result;
    703 }
    704 
    705 /*
    706  * Create a tree node for a binary operator and its two operands. Also called
    707  * for unary operators; in that case rn is NULL.
    708  *
    709  * Function calls, sizeof and casts are handled elsewhere.
    710  */
    711 tnode_t *
    712 build_binary(tnode_t *ln, op_t op, bool sys, tnode_t *rn)
    713 {
    714 	const mod_t *mp;
    715 	tnode_t	*ntn;
    716 	type_t	*rettp;
    717 
    718 	mp = &modtab[op];
    719 
    720 	/* If there was an error in one of the operands, return. */
    721 	if (ln == NULL || (mp->m_binary && rn == NULL))
    722 		return NULL;
    723 
    724 	/*
    725 	 * Apply class conversions to the left operand, but only if its
    726 	 * value is needed or it is compared with zero.
    727 	 */
    728 	if (mp->m_value_context || mp->m_compares_with_zero)
    729 		ln = cconv(ln);
    730 	/*
    731 	 * The right operand is almost always in a test or value context,
    732 	 * except if it is a struct or union member.
    733 	 */
    734 	if (mp->m_binary && op != ARROW && op != POINT)
    735 		rn = cconv(rn);
    736 
    737 	/*
    738 	 * Print some warnings for comparisons of unsigned values with
    739 	 * constants lower than or equal to null. This must be done
    740 	 * before promote() because otherwise unsigned char and unsigned
    741 	 * short would be promoted to int. Types are also tested to be
    742 	 * CHAR, which would also become int.
    743 	 */
    744 	if (mp->m_comparison)
    745 		check_integer_comparison(op, ln, rn);
    746 
    747 	if (mp->m_value_context || mp->m_compares_with_zero)
    748 		ln = promote(op, false, ln);
    749 	if (mp->m_binary && op != ARROW && op != POINT &&
    750 	    op != ASSIGN && op != RETURN && op != INIT) {
    751 		rn = promote(op, false, rn);
    752 	}
    753 
    754 	/*
    755 	 * If the result of the operation is different for signed or
    756 	 * unsigned operands and one of the operands is signed only in
    757 	 * ANSI C, print a warning.
    758 	 */
    759 	if (mp->m_warn_if_left_unsigned_in_c90 &&
    760 	    ln->tn_op == CON && ln->tn_val->v_unsigned_since_c90) {
    761 		/* ANSI C treats constant as unsigned, op %s */
    762 		warning(218, mp->m_name);
    763 		ln->tn_val->v_unsigned_since_c90 = false;
    764 	}
    765 	if (mp->m_warn_if_right_unsigned_in_c90 &&
    766 	    rn->tn_op == CON && rn->tn_val->v_unsigned_since_c90) {
    767 		/* ANSI C treats constant as unsigned, op %s */
    768 		warning(218, mp->m_name);
    769 		rn->tn_val->v_unsigned_since_c90 = false;
    770 	}
    771 
    772 	/* Make sure both operands are of the same type */
    773 	if (mp->m_balance_operands || (!allow_c90 && (op == SHL || op == SHR)))
    774 		balance(op, &ln, &rn);
    775 
    776 	/*
    777 	 * Check types for compatibility with the operation and mutual
    778 	 * compatibility. Return if there are serious problems.
    779 	 */
    780 	if (!typeok(op, 0, ln, rn))
    781 		return NULL;
    782 
    783 	/* And now create the node. */
    784 	switch (op) {
    785 	case POINT:
    786 	case ARROW:
    787 		ntn = build_struct_access(op, sys, ln, rn);
    788 		break;
    789 	case INCAFT:
    790 	case DECAFT:
    791 	case INCBEF:
    792 	case DECBEF:
    793 		ntn = build_prepost_incdec(op, sys, ln);
    794 		break;
    795 	case ADDR:
    796 		ntn = build_address(sys, ln, false);
    797 		break;
    798 	case INDIR:
    799 		ntn = new_tnode(INDIR, sys, ln->tn_type->t_subt, ln, NULL);
    800 		break;
    801 	case PLUS:
    802 	case MINUS:
    803 		ntn = build_plus_minus(op, sys, ln, rn);
    804 		break;
    805 	case SHL:
    806 	case SHR:
    807 		ntn = build_bit_shift(op, sys, ln, rn);
    808 		break;
    809 	case COLON:
    810 		ntn = build_colon(sys, ln, rn);
    811 		break;
    812 	case ASSIGN:
    813 	case MULASS:
    814 	case DIVASS:
    815 	case MODASS:
    816 	case ADDASS:
    817 	case SUBASS:
    818 	case SHLASS:
    819 	case SHRASS:
    820 	case ANDASS:
    821 	case XORASS:
    822 	case ORASS:
    823 	case RETURN:
    824 	case INIT:
    825 		ntn = build_assignment(op, sys, ln, rn);
    826 		break;
    827 	case COMMA:
    828 	case QUEST:
    829 		ntn = new_tnode(op, sys, rn->tn_type, ln, rn);
    830 		break;
    831 	case REAL:
    832 	case IMAG:
    833 		ntn = build_real_imag(op, sys, ln);
    834 		break;
    835 	default:
    836 		rettp = mp->m_returns_bool
    837 		    ? gettyp(Tflag ? BOOL : INT) : ln->tn_type;
    838 		lint_assert(mp->m_binary == (rn != NULL));
    839 		ntn = new_tnode(op, sys, rettp, ln, rn);
    840 		break;
    841 	}
    842 
    843 	/* Return if an error occurred. */
    844 	if (ntn == NULL)
    845 		return NULL;
    846 
    847 	/* Print a warning if precedence confusion is possible */
    848 	if (mp->m_possible_precedence_confusion)
    849 		check_precedence_confusion(ntn);
    850 
    851 	/*
    852 	 * Print a warning if one of the operands is in a context where
    853 	 * it is compared with zero and if this operand is a constant.
    854 	 */
    855 	if (hflag && !constcond_flag &&
    856 	    mp->m_compares_with_zero &&
    857 	    (ln->tn_op == CON ||
    858 	     ((mp->m_binary && op != QUEST) && rn->tn_op == CON)) &&
    859 	    /* XXX: rn->tn_system_dependent should be checked as well */
    860 	    !ln->tn_system_dependent) {
    861 		/* constant in conditional context */
    862 		warning(161);
    863 	}
    864 
    865 	/* Fold if the operator requires it */
    866 	if (mp->m_fold_constant_operands) {
    867 		if (ln->tn_op == CON && (!mp->m_binary || rn->tn_op == CON)) {
    868 			if (mp->m_compares_with_zero) {
    869 				ntn = fold_bool(ntn);
    870 			} else if (is_floating(ntn->tn_type->t_tspec)) {
    871 				ntn = fold_float(ntn);
    872 			} else {
    873 				ntn = fold(ntn);
    874 			}
    875 		} else if (op == QUEST && ln->tn_op == CON) {
    876 			ntn = ln->tn_val->v_quad != 0
    877 			    ? rn->tn_left : rn->tn_right;
    878 		}
    879 	}
    880 
    881 	return ntn;
    882 }
    883 
    884 tnode_t *
    885 build_unary(op_t op, bool sys, tnode_t *tn)
    886 {
    887 	return build_binary(tn, op, sys, NULL);
    888 }
    889 
    890 tnode_t *
    891 build_member_access(tnode_t *ln, op_t op, bool sys, sbuf_t *member)
    892 {
    893 	sym_t	*msym;
    894 
    895 	if (ln == NULL)
    896 		return NULL;
    897 
    898 	if (op == ARROW) {
    899 		/* must do this before struct_or_union_member is called */
    900 		ln = cconv(ln);
    901 	}
    902 	msym = struct_or_union_member(ln, op, getsym(member));
    903 	return build_binary(ln, op, sys, build_name(msym, false));
    904 }
    905 
    906 /*
    907  * Perform class conversions.
    908  *
    909  * Arrays of type T are converted into pointers to type T.
    910  * Functions are converted to pointers to functions.
    911  * Lvalues are converted to rvalues.
    912  *
    913  * C99 6.3 "Conversions"
    914  * C99 6.3.2 "Other operands"
    915  * C99 6.3.2.1 "Lvalues, arrays, and function designators"
    916  */
    917 tnode_t *
    918 cconv(tnode_t *tn)
    919 {
    920 	type_t	*tp;
    921 
    922 	/*
    923 	 * Array-lvalue (array of type T) is converted into rvalue
    924 	 * (pointer to type T)
    925 	 */
    926 	if (tn->tn_type->t_tspec == ARRAY) {
    927 		if (!tn->tn_lvalue) {
    928 			/* XXX print correct operator */
    929 			/* %soperand of '%s' must be lvalue */
    930 			gnuism(114, "", op_name(ADDR));
    931 		}
    932 		tn = new_tnode(ADDR, tn->tn_sys,
    933 		    expr_derive_type(tn->tn_type->t_subt, PTR), tn, NULL);
    934 	}
    935 
    936 	/*
    937 	 * Expression of type function (function with return value of type T)
    938 	 * in rvalue-expression (pointer to function with return value
    939 	 * of type T)
    940 	 */
    941 	if (tn->tn_type->t_tspec == FUNC)
    942 		tn = build_address(tn->tn_sys, tn, true);
    943 
    944 	/* lvalue to rvalue */
    945 	if (tn->tn_lvalue) {
    946 		tp = expr_dup_type(tn->tn_type);
    947 		/* C99 6.3.2.1p2 sentence 2 says to remove the qualifiers. */
    948 		tp->t_const = tp->t_volatile = false;
    949 		tn = new_tnode(LOAD, tn->tn_sys, tp, tn, NULL);
    950 	}
    951 
    952 	return tn;
    953 }
    954 
    955 const tnode_t *
    956 before_conversion(const tnode_t *tn)
    957 {
    958 	while (tn->tn_op == CVT && !tn->tn_cast)
    959 		tn = tn->tn_left;
    960 	return tn;
    961 }
    962 
    963 static bool
    964 is_null_pointer(const tnode_t *tn)
    965 {
    966 	tspec_t t = tn->tn_type->t_tspec;
    967 
    968 	return ((t == PTR && tn->tn_type->t_subt->t_tspec == VOID) ||
    969 		is_integer(t))
    970 	       && (tn->tn_op == CON && tn->tn_val->v_quad == 0);
    971 }
    972 
    973 /*
    974  * Most errors required by ANSI C are reported in struct_or_union_member().
    975  * Here we only check for totally wrong things.
    976  */
    977 static bool
    978 typeok_point(const tnode_t *ln, const type_t *ltp, tspec_t lt)
    979 {
    980 	if (is_struct_or_union(lt))
    981 		return true;
    982 
    983 	if (lt == FUNC || lt == VOID || ltp->t_bitfield)
    984 		goto wrong;
    985 
    986 	/*
    987 	 * Some C dialects from before C90 tolerated any lvalue on the
    988 	 * left-hand side of the '.' operator, allowing things like
    989 	 * char st[100]; st.st_mtime, assuming that the member 'st_mtime'
    990 	 * only occurred in a single struct; see typeok_arrow.
    991 	 */
    992 	if (ln->tn_lvalue)
    993 		return true;
    994 
    995 wrong:
    996 	/* With allow_c90 we already got an error */
    997 	if (!allow_c90)
    998 		/* unacceptable operand of '%s' */
    999 		error(111, op_name(POINT));
   1000 
   1001 	return false;
   1002 }
   1003 
   1004 static bool
   1005 typeok_arrow(tspec_t lt)
   1006 {
   1007 	/*
   1008 	 * C1978 Appendix A 14.1 says: <quote>In fact, any lvalue is allowed
   1009 	 * before '.', and that lvalue is then assumed to have the form of
   1010 	 * the structure of which the name of the right is a member. [...]
   1011 	 * Such constructions are non-portable.</quote>
   1012 	 */
   1013 	if (lt == PTR || (!allow_c90 && is_integer(lt)))
   1014 		return true;
   1015 
   1016 	/* With allow_c90 we already got an error */
   1017 	if (!allow_c90)
   1018 		/* unacceptable operand of '%s' */
   1019 		error(111, op_name(ARROW));
   1020 	return false;
   1021 }
   1022 
   1023 static bool
   1024 typeok_incdec(op_t op, const tnode_t *tn, const type_t *tp)
   1025 {
   1026 	/* operand has scalar type (checked in typeok) */
   1027 	if (!tn->tn_lvalue) {
   1028 		if (tn->tn_op == CVT && tn->tn_cast &&
   1029 		    tn->tn_left->tn_op == LOAD) {
   1030 			/* a cast does not yield an lvalue */
   1031 			error(163);
   1032 		}
   1033 		/* %soperand of '%s' must be lvalue */
   1034 		error(114, "", op_name(op));
   1035 		return false;
   1036 	} else if (tp->t_const) {
   1037 		if (allow_c90)
   1038 			/* %soperand of '%s' must be modifiable lvalue */
   1039 			warning(115, "", op_name(op));
   1040 	}
   1041 	return true;
   1042 }
   1043 
   1044 static bool
   1045 typeok_address(const mod_t *mp,
   1046 	       const tnode_t *tn, const type_t *tp, tspec_t t)
   1047 {
   1048 	if (t == ARRAY || t == FUNC) {
   1049 		/* ok, a warning comes later (in build_address()) */
   1050 	} else if (!tn->tn_lvalue) {
   1051 		if (tn->tn_op == CVT && tn->tn_cast &&
   1052 		    tn->tn_left->tn_op == LOAD) {
   1053 			/* a cast does not yield an lvalue */
   1054 			error(163);
   1055 		}
   1056 		/* %soperand of '%s' must be lvalue */
   1057 		error(114, "", mp->m_name);
   1058 		return false;
   1059 	} else if (is_scalar(t)) {
   1060 		if (tp->t_bitfield) {
   1061 			/* cannot take address of bit-field */
   1062 			error(112);
   1063 			return false;
   1064 		}
   1065 	} else if (t != STRUCT && t != UNION) {
   1066 		/* unacceptable operand of '%s' */
   1067 		error(111, mp->m_name);
   1068 		return false;
   1069 	}
   1070 	if (tn->tn_op == NAME && tn->tn_sym->s_register) {
   1071 		/* cannot take address of register %s */
   1072 		error(113, tn->tn_sym->s_name);
   1073 		return false;
   1074 	}
   1075 	return true;
   1076 }
   1077 
   1078 static bool
   1079 typeok_indir(const type_t *tp, tspec_t t)
   1080 {
   1081 
   1082 	if (t != PTR) {
   1083 		/* cannot dereference non-pointer type '%s' */
   1084 		error(96, type_name(tp));
   1085 		return false;
   1086 	}
   1087 	return true;
   1088 }
   1089 
   1090 static bool
   1091 typeok_plus(op_t op,
   1092 	    const type_t *ltp, tspec_t lt,
   1093 	    const type_t *rtp, tspec_t rt)
   1094 {
   1095 	/* operands have scalar types (checked in typeok) */
   1096 	if ((lt == PTR && !is_integer(rt)) || (rt == PTR && !is_integer(lt))) {
   1097 		warn_incompatible_types(op, ltp, lt, rtp, rt);
   1098 		return false;
   1099 	}
   1100 	return true;
   1101 }
   1102 
   1103 static bool
   1104 typeok_minus(op_t op,
   1105 	     const type_t *ltp, tspec_t lt,
   1106 	     const type_t *rtp, tspec_t rt)
   1107 {
   1108 	/* operands have scalar types (checked in typeok) */
   1109 	if (lt == PTR && (!is_integer(rt) && rt != PTR)) {
   1110 		warn_incompatible_types(op, ltp, lt, rtp, rt);
   1111 		return false;
   1112 	} else if (rt == PTR && lt != PTR) {
   1113 		warn_incompatible_types(op, ltp, lt, rtp, rt);
   1114 		return false;
   1115 	}
   1116 	if (lt == PTR && rt == PTR) {
   1117 		if (!eqtype(ltp->t_subt, rtp->t_subt, true, false, NULL)) {
   1118 			/* illegal pointer subtraction */
   1119 			error(116);
   1120 		}
   1121 	}
   1122 	return true;
   1123 }
   1124 
   1125 static void
   1126 typeok_shr(const mod_t *mp,
   1127 	   const tnode_t *ln, tspec_t lt,
   1128 	   const tnode_t *rn, tspec_t rt)
   1129 {
   1130 	tspec_t olt, ort;
   1131 
   1132 	olt = before_conversion(ln)->tn_type->t_tspec;
   1133 	ort = before_conversion(rn)->tn_type->t_tspec;
   1134 
   1135 	/* operands have integer types (checked in typeok) */
   1136 	if (pflag && !is_uinteger(olt)) {
   1137 		/*
   1138 		 * The left operand is signed. This means that
   1139 		 * the operation is (possibly) nonportable.
   1140 		 */
   1141 		if (ln->tn_op != CON) {
   1142 			/* bitwise '%s' on signed value possibly nonportable */
   1143 			warning(117, mp->m_name);
   1144 		} else if (ln->tn_val->v_quad < 0) {
   1145 			/* bitwise '%s' on signed value nonportable */
   1146 			warning(120, mp->m_name);
   1147 		}
   1148 	} else if (allow_trad && allow_c90 &&
   1149 		   !is_uinteger(olt) && is_uinteger(ort)) {
   1150 		/*
   1151 		 * The left operand would become unsigned in
   1152 		 * traditional C.
   1153 		 */
   1154 		if (hflag && (ln->tn_op != CON || ln->tn_val->v_quad < 0)) {
   1155 			/* semantics of '%s' change in ANSI C; use ... */
   1156 			warning(118, mp->m_name);
   1157 		}
   1158 	} else if (allow_trad && allow_c90 &&
   1159 		   !is_uinteger(olt) && !is_uinteger(ort) &&
   1160 		   portable_size_in_bits(lt) < portable_size_in_bits(rt)) {
   1161 		/*
   1162 		 * In traditional C the left operand would be extended
   1163 		 * (possibly sign-extended) and then shifted.
   1164 		 */
   1165 		if (hflag && (ln->tn_op != CON || ln->tn_val->v_quad < 0)) {
   1166 			/* semantics of '%s' change in ANSI C; use ... */
   1167 			warning(118, mp->m_name);
   1168 		}
   1169 	}
   1170 }
   1171 
   1172 static void
   1173 typeok_shl(const mod_t *mp, tspec_t lt, tspec_t rt)
   1174 {
   1175 	/*
   1176 	 * C90 does not perform balancing for shift operations,
   1177 	 * but traditional C does. If the width of the right operand
   1178 	 * is greater than the width of the left operand, then in
   1179 	 * traditional C the left operand would be extended to the
   1180 	 * width of the right operand. For SHL this may result in
   1181 	 * different results.
   1182 	 */
   1183 	if (portable_size_in_bits(lt) < portable_size_in_bits(rt)) {
   1184 		/*
   1185 		 * XXX If both operands are constant, make sure
   1186 		 * that there is really a difference between
   1187 		 * ANSI C and traditional C.
   1188 		 */
   1189 		if (hflag && !allow_c99)
   1190 			/* semantics of '%s' change in ANSI C; use ... */
   1191 			warning(118, mp->m_name);
   1192 	}
   1193 }
   1194 
   1195 static void
   1196 typeok_shift(tspec_t lt, const tnode_t *rn, tspec_t rt)
   1197 {
   1198 	if (rn->tn_op != CON)
   1199 		return;
   1200 
   1201 	if (!is_uinteger(rt) && rn->tn_val->v_quad < 0) {
   1202 		/* negative shift */
   1203 		warning(121);
   1204 	} else if ((uint64_t)rn->tn_val->v_quad ==
   1205 		   (uint64_t)size_in_bits(lt)) {
   1206 		/* shift equal to size of object */
   1207 		warning(267);
   1208 	} else if ((uint64_t)rn->tn_val->v_quad > (uint64_t)size_in_bits(lt)) {
   1209 		/* shift amount %llu is greater than bit-size %llu of '%s' */
   1210 		warning(122, (unsigned long long)rn->tn_val->v_quad,
   1211 		    (unsigned long long)size_in_bits(lt),
   1212 		    tspec_name(lt));
   1213 	}
   1214 }
   1215 
   1216 static bool
   1217 is_typeok_eq(const tnode_t *ln, tspec_t lt, const tnode_t *rn, tspec_t rt)
   1218 {
   1219 	if (lt == PTR && is_null_pointer(rn))
   1220 		return true;
   1221 	if (rt == PTR && is_null_pointer(ln))
   1222 		return true;
   1223 	return false;
   1224 }
   1225 
   1226 static bool
   1227 typeok_compare(op_t op,
   1228 	       const tnode_t *ln, const type_t *ltp, tspec_t lt,
   1229 	       const tnode_t *rn, const type_t *rtp, tspec_t rt)
   1230 {
   1231 	const char *lx, *rx;
   1232 
   1233 	if (lt == PTR && rt == PTR) {
   1234 		check_pointer_comparison(op, ln, rn);
   1235 		return true;
   1236 	}
   1237 
   1238 	if (lt != PTR && rt != PTR)
   1239 		return true;
   1240 
   1241 	if (!is_integer(lt) && !is_integer(rt)) {
   1242 		warn_incompatible_types(op, ltp, lt, rtp, rt);
   1243 		return false;
   1244 	}
   1245 
   1246 	lx = lt == PTR ? "pointer" : "integer";
   1247 	rx = rt == PTR ? "pointer" : "integer";
   1248 	/* illegal combination of %s '%s' and %s '%s', op '%s' */
   1249 	warning(123, lx, type_name(ltp), rx, type_name(rtp), op_name(op));
   1250 	return true;
   1251 }
   1252 
   1253 static bool
   1254 typeok_quest(tspec_t lt, const tnode_t *rn)
   1255 {
   1256 	if (!is_scalar(lt)) {
   1257 		/* first operand must have scalar type, op ? : */
   1258 		error(170);
   1259 		return false;
   1260 	}
   1261 	lint_assert(before_conversion(rn)->tn_op == COLON);
   1262 	return true;
   1263 }
   1264 
   1265 static void
   1266 typeok_colon_pointer(const mod_t *mp, const type_t *ltp, const type_t *rtp)
   1267 {
   1268 	type_t *lstp = ltp->t_subt;
   1269 	type_t *rstp = rtp->t_subt;
   1270 	tspec_t lst = lstp->t_tspec;
   1271 	tspec_t rst = rstp->t_tspec;
   1272 
   1273 	if ((lst == VOID && rst == FUNC) || (lst == FUNC && rst == VOID)) {
   1274 		/* (void *)0 is handled in typeok_colon */
   1275 		/* TODO: C99 behaves like C90 here. */
   1276 		if (!allow_trad && !allow_c99)
   1277 			/* ANSI C forbids conversion of %s to %s, op %s */
   1278 			warning(305, "function pointer", "'void *'",
   1279 			    mp->m_name);
   1280 		return;
   1281 	}
   1282 
   1283 	if (eqptrtype(lstp, rstp, true))
   1284 		return;
   1285 	if (!eqtype(lstp, rstp, true, false, NULL))
   1286 		warn_incompatible_pointers(mp, ltp, rtp);
   1287 }
   1288 
   1289 static bool
   1290 typeok_colon(const mod_t *mp,
   1291 	     const tnode_t *ln, const type_t *ltp, tspec_t lt,
   1292 	     const tnode_t *rn, const type_t *rtp, tspec_t rt)
   1293 {
   1294 
   1295 	if (is_arithmetic(lt) && is_arithmetic(rt))
   1296 		return true;
   1297 	if (lt == BOOL && rt == BOOL)
   1298 		return true;
   1299 
   1300 	if (lt == STRUCT && rt == STRUCT && ltp->t_str == rtp->t_str)
   1301 		return true;
   1302 	if (lt == UNION && rt == UNION && ltp->t_str == rtp->t_str)
   1303 		return true;
   1304 
   1305 	if (lt == PTR && is_null_pointer(rn))
   1306 		return true;
   1307 	if (rt == PTR && is_null_pointer(ln))
   1308 		return true;
   1309 
   1310 	if ((lt == PTR && is_integer(rt)) || (is_integer(lt) && rt == PTR)) {
   1311 		const char *lx = lt == PTR ? "pointer" : "integer";
   1312 		const char *rx = rt == PTR ? "pointer" : "integer";
   1313 		/* illegal combination of %s '%s' and %s '%s', op '%s' */
   1314 		warning(123, lx, type_name(ltp),
   1315 		    rx, type_name(rtp), mp->m_name);
   1316 		return true;
   1317 	}
   1318 
   1319 	if (lt == VOID || rt == VOID) {
   1320 		if (lt != VOID || rt != VOID)
   1321 			/* incompatible types '%s' and '%s' in conditional */
   1322 			warning(126, type_name(ltp), type_name(rtp));
   1323 		return true;
   1324 	}
   1325 
   1326 	if (lt == PTR && rt == PTR) {
   1327 		typeok_colon_pointer(mp, ltp, rtp);
   1328 		return true;
   1329 	}
   1330 
   1331 	/* incompatible types '%s' and '%s' in conditional */
   1332 	error(126, type_name(ltp), type_name(rtp));
   1333 	return false;
   1334 }
   1335 
   1336 static bool
   1337 typeok_assign(op_t op, const tnode_t *ln, const type_t *ltp, tspec_t lt)
   1338 {
   1339 	if (op == RETURN || op == INIT || op == FARG)
   1340 		return true;
   1341 
   1342 	if (!ln->tn_lvalue) {
   1343 		if (ln->tn_op == CVT && ln->tn_cast &&
   1344 		    ln->tn_left->tn_op == LOAD) {
   1345 			/* a cast does not yield an lvalue */
   1346 			error(163);
   1347 		}
   1348 		/* %soperand of '%s' must be lvalue */
   1349 		error(114, "left ", op_name(op));
   1350 		return false;
   1351 	} else if (ltp->t_const || (is_struct_or_union(lt) &&
   1352 				    has_constant_member(ltp))) {
   1353 		if (allow_c90)
   1354 			/* %soperand of '%s' must be modifiable lvalue */
   1355 			warning(115, "left ", op_name(op));
   1356 	}
   1357 	return true;
   1358 }
   1359 
   1360 /* Check the types using the information from modtab[]. */
   1361 static bool
   1362 typeok_scalar(op_t op, const mod_t *mp,
   1363 	      const type_t *ltp, tspec_t lt,
   1364 	      const type_t *rtp, tspec_t rt)
   1365 {
   1366 	if (mp->m_takes_bool && lt == BOOL && rt == BOOL)
   1367 		return true;
   1368 	if (mp->m_requires_integer) {
   1369 		if (!is_integer(lt) || (mp->m_binary && !is_integer(rt))) {
   1370 			warn_incompatible_types(op, ltp, lt, rtp, rt);
   1371 			return false;
   1372 		}
   1373 	} else if (mp->m_requires_integer_or_complex) {
   1374 		if ((!is_integer(lt) && !is_complex(lt)) ||
   1375 		    (mp->m_binary && (!is_integer(rt) && !is_complex(rt)))) {
   1376 			warn_incompatible_types(op, ltp, lt, rtp, rt);
   1377 			return false;
   1378 		}
   1379 	} else if (mp->m_requires_scalar) {
   1380 		if (!is_scalar(lt) || (mp->m_binary && !is_scalar(rt))) {
   1381 			warn_incompatible_types(op, ltp, lt, rtp, rt);
   1382 			return false;
   1383 		}
   1384 	} else if (mp->m_requires_arith) {
   1385 		if (!is_arithmetic(lt) ||
   1386 		    (mp->m_binary && !is_arithmetic(rt))) {
   1387 			warn_incompatible_types(op, ltp, lt, rtp, rt);
   1388 			return false;
   1389 		}
   1390 	}
   1391 	return true;
   1392 }
   1393 
   1394 /*
   1395  * Check the types for specific operators and type combinations.
   1396  *
   1397  * At this point, the operands already conform to the type requirements of
   1398  * the operator, such as being integer, floating or scalar.
   1399  */
   1400 static bool
   1401 typeok_op(op_t op, const mod_t *mp, int arg,
   1402 	  const tnode_t *ln, const type_t *ltp, tspec_t lt,
   1403 	  const tnode_t *rn, const type_t *rtp, tspec_t rt)
   1404 {
   1405 	switch (op) {
   1406 	case ARROW:
   1407 		return typeok_arrow(lt);
   1408 	case POINT:
   1409 		return typeok_point(ln, ltp, lt);
   1410 	case INCBEF:
   1411 	case DECBEF:
   1412 	case INCAFT:
   1413 	case DECAFT:
   1414 		return typeok_incdec(op, ln, ltp);
   1415 	case INDIR:
   1416 		return typeok_indir(ltp, lt);
   1417 	case ADDR:
   1418 		return typeok_address(mp, ln, ltp, lt);
   1419 	case PLUS:
   1420 		return typeok_plus(op, ltp, lt, rtp, rt);
   1421 	case MINUS:
   1422 		return typeok_minus(op, ltp, lt, rtp, rt);
   1423 	case SHL:
   1424 		typeok_shl(mp, lt, rt);
   1425 		goto shift;
   1426 	case SHR:
   1427 		typeok_shr(mp, ln, lt, rn, rt);
   1428 	shift:
   1429 		typeok_shift(lt, rn, rt);
   1430 		break;
   1431 	case LT:
   1432 	case LE:
   1433 	case GT:
   1434 	case GE:
   1435 	compare:
   1436 		return typeok_compare(op, ln, ltp, lt, rn, rtp, rt);
   1437 	case EQ:
   1438 	case NE:
   1439 		if (is_typeok_eq(ln, lt, rn, rt))
   1440 			break;
   1441 		goto compare;
   1442 	case QUEST:
   1443 		return typeok_quest(lt, rn);
   1444 	case COLON:
   1445 		return typeok_colon(mp, ln, ltp, lt, rn, rtp, rt);
   1446 	case ASSIGN:
   1447 	case INIT:
   1448 	case FARG:
   1449 	case RETURN:
   1450 		if (!check_assign_types_compatible(op, arg, ln, rn))
   1451 			return false;
   1452 		goto assign;
   1453 	case MULASS:
   1454 	case DIVASS:
   1455 	case MODASS:
   1456 		goto assign;
   1457 	case ADDASS:
   1458 	case SUBASS:
   1459 		if ((lt == PTR && !is_integer(rt)) || rt == PTR) {
   1460 			warn_incompatible_types(op, ltp, lt, rtp, rt);
   1461 			return false;
   1462 		}
   1463 		goto assign;
   1464 	case SHLASS:
   1465 		goto assign;
   1466 	case SHRASS:
   1467 		if (pflag && !is_uinteger(lt) &&
   1468 		    !(!allow_c90 && is_uinteger(rt))) {
   1469 			/* bitwise '%s' on signed value possibly nonportable */
   1470 			warning(117, mp->m_name);
   1471 		}
   1472 		goto assign;
   1473 	case ANDASS:
   1474 	case XORASS:
   1475 	case ORASS:
   1476 	assign:
   1477 		return typeok_assign(op, ln, ltp, lt);
   1478 	case COMMA:
   1479 		if (!modtab[ln->tn_op].m_has_side_effect)
   1480 			check_null_effect(ln);
   1481 		break;
   1482 	default:
   1483 		break;
   1484 	}
   1485 	return true;
   1486 }
   1487 
   1488 static void
   1489 typeok_enum(op_t op, const mod_t *mp, int arg,
   1490 	    const tnode_t *ln, const type_t *ltp,
   1491 	    const tnode_t *rn, const type_t *rtp)
   1492 {
   1493 	if (mp->m_bad_on_enum &&
   1494 	    (ltp->t_is_enum || (mp->m_binary && rtp->t_is_enum))) {
   1495 		check_bad_enum_operation(op, ln, rn);
   1496 	} else if (mp->m_valid_on_enum &&
   1497 		   (ltp->t_is_enum && rtp != NULL && rtp->t_is_enum)) {
   1498 		check_enum_type_mismatch(op, arg, ln, rn);
   1499 	} else if (mp->m_valid_on_enum &&
   1500 		   (ltp->t_is_enum || (rtp != NULL && rtp->t_is_enum))) {
   1501 		check_enum_int_mismatch(op, arg, ln, rn);
   1502 	}
   1503 }
   1504 
   1505 /* Perform most type checks. Return whether the types are ok. */
   1506 bool
   1507 typeok(op_t op, int arg, const tnode_t *ln, const tnode_t *rn)
   1508 {
   1509 	const mod_t *mp;
   1510 	tspec_t	lt, rt;
   1511 	type_t	*ltp, *rtp;
   1512 
   1513 	mp = &modtab[op];
   1514 
   1515 	lint_assert((ltp = ln->tn_type) != NULL);
   1516 	lt = ltp->t_tspec;
   1517 
   1518 	if (mp->m_binary) {
   1519 		lint_assert((rtp = rn->tn_type) != NULL);
   1520 		rt = rtp->t_tspec;
   1521 	} else {
   1522 		rtp = NULL;
   1523 		rt = NOTSPEC;
   1524 	}
   1525 
   1526 	if (Tflag && !typeok_scalar_strict_bool(op, mp, arg, ln, rn))
   1527 		return false;
   1528 	if (!typeok_scalar(op, mp, ltp, lt, rtp, rt))
   1529 		return false;
   1530 
   1531 	if (!typeok_op(op, mp, arg, ln, ltp, lt, rn, rtp, rt))
   1532 		return false;
   1533 
   1534 	typeok_enum(op, mp, arg, ln, ltp, rn, rtp);
   1535 	return true;
   1536 }
   1537 
   1538 static void
   1539 check_pointer_comparison(op_t op, const tnode_t *ln, const tnode_t *rn)
   1540 {
   1541 	type_t	*ltp, *rtp;
   1542 	tspec_t	lst, rst;
   1543 	const	char *lsts, *rsts;
   1544 
   1545 	lst = (ltp = ln->tn_type)->t_subt->t_tspec;
   1546 	rst = (rtp = rn->tn_type)->t_subt->t_tspec;
   1547 
   1548 	if (lst == VOID || rst == VOID) {
   1549 		/* TODO: C99 behaves like C90 here. */
   1550 		if ((!allow_trad && !allow_c99) &&
   1551 		    (lst == FUNC || rst == FUNC)) {
   1552 			/* (void *)0 already handled in typeok() */
   1553 			*(lst == FUNC ? &lsts : &rsts) = "function pointer";
   1554 			*(lst == VOID ? &lsts : &rsts) = "'void *'";
   1555 			/* ANSI C forbids comparison of %s with %s */
   1556 			warning(274, lsts, rsts);
   1557 		}
   1558 		return;
   1559 	}
   1560 
   1561 	if (!eqtype(ltp->t_subt, rtp->t_subt, true, false, NULL)) {
   1562 		warn_incompatible_pointers(&modtab[op], ltp, rtp);
   1563 		return;
   1564 	}
   1565 
   1566 	if (lst == FUNC && rst == FUNC) {
   1567 		/* TODO: C99 behaves like C90 here, see C99 6.5.8p2. */
   1568 		if ((!allow_trad && !allow_c99) && op != EQ && op != NE)
   1569 			/* ANSI C forbids ordered comparisons of ... */
   1570 			warning(125);
   1571 	}
   1572 }
   1573 
   1574 static bool
   1575 is_direct_function_call(const tnode_t *tn, const char **out_name)
   1576 {
   1577 
   1578 	if (!(tn->tn_op == CALL &&
   1579 	      tn->tn_left->tn_op == ADDR &&
   1580 	      tn->tn_left->tn_left->tn_op == NAME))
   1581 		return false;
   1582 
   1583 	*out_name = tn->tn_left->tn_left->tn_sym->s_name;
   1584 	return true;
   1585 }
   1586 
   1587 static bool
   1588 is_unconst_function(const char *name)
   1589 {
   1590 
   1591 	return strcmp(name, "memchr") == 0 ||
   1592 	       strcmp(name, "strchr") == 0 ||
   1593 	       strcmp(name, "strpbrk") == 0 ||
   1594 	       strcmp(name, "strrchr") == 0 ||
   1595 	       strcmp(name, "strstr") == 0;
   1596 }
   1597 
   1598 static bool
   1599 is_const_char_pointer(const tnode_t *tn)
   1600 {
   1601 	const type_t *tp;
   1602 
   1603 	/*
   1604 	 * For traditional reasons, C99 6.4.5p5 defines that string literals
   1605 	 * have type 'char[]'.  They are often implicitly converted to
   1606 	 * 'char *', for example when they are passed as function arguments.
   1607 	 *
   1608 	 * C99 6.4.5p6 further defines that modifying a string that is
   1609 	 * constructed from a string literal invokes undefined behavior.
   1610 	 *
   1611 	 * Out of these reasons, string literals are treated as 'effectively
   1612 	 * const' here.
   1613 	 */
   1614 	if (tn->tn_op == CVT &&
   1615 	    tn->tn_left->tn_op == ADDR &&
   1616 	    tn->tn_left->tn_left->tn_op == STRING)
   1617 		return true;
   1618 
   1619 	tp = before_conversion(tn)->tn_type;
   1620 	return tp->t_tspec == PTR &&
   1621 	       tp->t_subt->t_tspec == CHAR &&
   1622 	       tp->t_subt->t_const;
   1623 }
   1624 
   1625 static bool
   1626 is_const_pointer(const tnode_t *tn)
   1627 {
   1628 	const type_t *tp;
   1629 
   1630 	tp = before_conversion(tn)->tn_type;
   1631 	return tp->t_tspec == PTR && tp->t_subt->t_const;
   1632 }
   1633 
   1634 static bool
   1635 is_first_arg_const_char_pointer(const tnode_t *tn)
   1636 {
   1637 	const tnode_t *an;
   1638 
   1639 	an = tn->tn_right;
   1640 	if (an == NULL)
   1641 		return false;
   1642 
   1643 	while (an->tn_right != NULL)
   1644 		an = an->tn_right;
   1645 	return is_const_char_pointer(an->tn_left);
   1646 }
   1647 
   1648 static bool
   1649 is_second_arg_const_pointer(const tnode_t *tn)
   1650 {
   1651 	const tnode_t *an;
   1652 
   1653 	an = tn->tn_right;
   1654 	if (an == NULL || an->tn_right == NULL)
   1655 		return false;
   1656 
   1657 	while (an->tn_right->tn_right != NULL)
   1658 		an = an->tn_right;
   1659 	return is_const_pointer(an->tn_left);
   1660 }
   1661 
   1662 static void
   1663 check_unconst_function(const type_t *lstp, const tnode_t *rn)
   1664 {
   1665 	const char *function_name;
   1666 
   1667 	if (lstp->t_tspec == CHAR && !lstp->t_const &&
   1668 	    is_direct_function_call(rn, &function_name) &&
   1669 	    is_unconst_function(function_name) &&
   1670 	    is_first_arg_const_char_pointer(rn)) {
   1671 		/* call to '%s' effectively discards 'const' from argument */
   1672 		warning(346, function_name);
   1673 	}
   1674 
   1675 	if (!lstp->t_const &&
   1676 	    is_direct_function_call(rn, &function_name) &&
   1677 	    strcmp(function_name, "bsearch") == 0 &&
   1678 	    is_second_arg_const_pointer(rn)) {
   1679 		/* call to '%s' effectively discards 'const' from argument */
   1680 		warning(346, function_name);
   1681 	}
   1682 }
   1683 
   1684 static void
   1685 check_assign_void_pointer(op_t op, int arg,
   1686 			  tspec_t lt, tspec_t lst,
   1687 			  tspec_t rt, tspec_t rst)
   1688 {
   1689 	const char *lts, *rts;
   1690 
   1691 	if (!(lt == PTR && rt == PTR && (lst == VOID || rst == VOID)))
   1692 		return;
   1693 	/* two pointers, at least one pointer to void */
   1694 
   1695 	/* TODO: C99 behaves like C90 here. */
   1696 	if (!((!allow_trad && !allow_c99) && (lst == FUNC || rst == FUNC)))
   1697 		return;
   1698 	/* comb. of ptr to func and ptr to void */
   1699 
   1700 	*(lst == FUNC ? &lts : &rts) = "function pointer";
   1701 	*(lst == VOID ? &lts : &rts) = "'void *'";
   1702 
   1703 	switch (op) {
   1704 	case INIT:
   1705 	case RETURN:
   1706 		/* ANSI C forbids conversion of %s to %s */
   1707 		warning(303, rts, lts);
   1708 		break;
   1709 	case FARG:
   1710 		/* ANSI C forbids conversion of %s to %s, arg #%d */
   1711 		warning(304, rts, lts, arg);
   1712 		break;
   1713 	default:
   1714 		/* ANSI C forbids conversion of %s to %s, op %s */
   1715 		warning(305, rts, lts, op_name(op));
   1716 		break;
   1717 	}
   1718 }
   1719 
   1720 static bool
   1721 check_assign_void_pointer_compat(op_t op, int arg,
   1722 				 const type_t *const ltp, tspec_t const lt,
   1723 				 const type_t *const lstp, tspec_t const lst,
   1724 				 const tnode_t *const rn,
   1725 				 const type_t *const rtp, tspec_t const rt,
   1726 				 const type_t *const rstp, tspec_t const rst)
   1727 {
   1728 	if (!(lt == PTR && rt == PTR && (lst == VOID || rst == VOID ||
   1729 					 eqtype(lstp, rstp, true, false, NULL))))
   1730 		return false;
   1731 
   1732 	/* compatible pointer types (qualifiers ignored) */
   1733 	if (allow_c90 &&
   1734 	    ((!lstp->t_const && rstp->t_const) ||
   1735 	     (!lstp->t_volatile && rstp->t_volatile))) {
   1736 		/* left side has not all qualifiers of right */
   1737 		switch (op) {
   1738 		case INIT:
   1739 		case RETURN:
   1740 			/* incompatible pointer types (%s != %s) */
   1741 			warning(182, type_name(lstp), type_name(rstp));
   1742 			break;
   1743 		case FARG:
   1744 			/* converting '%s' to incompatible '%s' ... */
   1745 			warning(153,
   1746 			    type_name(rtp), type_name(ltp), arg);
   1747 			break;
   1748 		default:
   1749 			/* operands have incompatible pointer type... */
   1750 			warning(128, op_name(op),
   1751 			    type_name(lstp), type_name(rstp));
   1752 			break;
   1753 		}
   1754 	}
   1755 
   1756 	if (allow_c90)
   1757 		check_unconst_function(lstp, rn);
   1758 
   1759 	return true;
   1760 }
   1761 
   1762 static bool
   1763 check_assign_pointer_integer(op_t op, int arg,
   1764 			     const type_t *const ltp, tspec_t const lt,
   1765 			     const type_t *const rtp, tspec_t const rt)
   1766 {
   1767 	const char *lx, *rx;
   1768 
   1769 	if (!((lt == PTR && is_integer(rt)) || (is_integer(lt) && rt == PTR)))
   1770 		return false;
   1771 
   1772 	lx = lt == PTR ? "pointer" : "integer";
   1773 	rx = rt == PTR ? "pointer" : "integer";
   1774 
   1775 	switch (op) {
   1776 	case INIT:
   1777 	case RETURN:
   1778 		/* illegal combination of %s (%s) and %s (%s) */
   1779 		warning(183, lx, type_name(ltp), rx, type_name(rtp));
   1780 		break;
   1781 	case FARG:
   1782 		/* illegal combination of %s (%s) and %s (%s), arg #%d */
   1783 		warning(154,
   1784 		    lx, type_name(ltp), rx, type_name(rtp), arg);
   1785 		break;
   1786 	default:
   1787 		/* illegal combination of %s '%s' and %s '%s', op '%s' */
   1788 		warning(123,
   1789 		    lx, type_name(ltp), rx, type_name(rtp), op_name(op));
   1790 		break;
   1791 	}
   1792 	return true;
   1793 }
   1794 
   1795 static bool
   1796 check_assign_pointer(op_t op, int arg,
   1797 		     const type_t *ltp, tspec_t lt,
   1798 		     const type_t *rtp, tspec_t rt)
   1799 {
   1800 	if (!(lt == PTR && rt == PTR))
   1801 		return false;
   1802 
   1803 	switch (op) {
   1804 	case RETURN:
   1805 		warn_incompatible_pointers(NULL, ltp, rtp);
   1806 		break;
   1807 	case FARG:
   1808 		/* converting '%s' to incompatible '%s' for ... */
   1809 		warning(153, type_name(rtp), type_name(ltp), arg);
   1810 		break;
   1811 	default:
   1812 		warn_incompatible_pointers(&modtab[op], ltp, rtp);
   1813 		break;
   1814 	}
   1815 	return true;
   1816 }
   1817 
   1818 static void
   1819 warn_assign(op_t op, int arg,
   1820 	    const type_t *ltp, tspec_t lt,
   1821 	    const type_t *rtp, tspec_t rt)
   1822 {
   1823 	switch (op) {
   1824 	case INIT:
   1825 		/* cannot initialize '%s' from '%s' */
   1826 		error(185, type_name(ltp), type_name(rtp));
   1827 		break;
   1828 	case RETURN:
   1829 		/* return value type mismatch (%s) and (%s) */
   1830 		error(211, type_name(ltp), type_name(rtp));
   1831 		break;
   1832 	case FARG:
   1833 		/* passing '%s' to incompatible '%s', arg #%d */
   1834 		warning(155, type_name(rtp), type_name(ltp), arg);
   1835 		break;
   1836 	default:
   1837 		warn_incompatible_types(op, ltp, lt, rtp, rt);
   1838 		break;
   1839 	}
   1840 }
   1841 
   1842 /*
   1843  * Checks type compatibility for ASSIGN, INIT, FARG and RETURN
   1844  * and prints warnings/errors if necessary.
   1845  * Returns whether the types are (almost) compatible.
   1846  */
   1847 static bool
   1848 check_assign_types_compatible(op_t op, int arg,
   1849 			      const tnode_t *ln, const tnode_t *rn)
   1850 {
   1851 	tspec_t	lt, rt, lst = NOTSPEC, rst = NOTSPEC;
   1852 	type_t	*ltp, *rtp, *lstp = NULL, *rstp = NULL;
   1853 
   1854 	if ((lt = (ltp = ln->tn_type)->t_tspec) == PTR)
   1855 		lst = (lstp = ltp->t_subt)->t_tspec;
   1856 	if ((rt = (rtp = rn->tn_type)->t_tspec) == PTR)
   1857 		rst = (rstp = rtp->t_subt)->t_tspec;
   1858 
   1859 	if (lt == BOOL && is_scalar(rt))	/* C99 6.3.1.2 */
   1860 		return true;
   1861 
   1862 	if (is_arithmetic(lt) && (is_arithmetic(rt) || rt == BOOL))
   1863 		return true;
   1864 
   1865 	if (is_struct_or_union(lt) && is_struct_or_union(rt))
   1866 		/* both are struct or union */
   1867 		return ltp->t_str == rtp->t_str;
   1868 
   1869 	/* a null pointer may be assigned to any pointer */
   1870 	if (lt == PTR && is_null_pointer(rn))
   1871 		return true;
   1872 
   1873 	check_assign_void_pointer(op, arg, lt, lst, rt, rst);
   1874 
   1875 	if (check_assign_void_pointer_compat(op, arg,
   1876 	    ltp, lt, lstp, lst, rn, rtp, rt, rstp, rst))
   1877 		return true;
   1878 
   1879 	if (check_assign_pointer_integer(op, arg, ltp, lt, rtp, rt))
   1880 		return true;
   1881 
   1882 	if (check_assign_pointer(op, arg, ltp, lt, rtp, rt))
   1883 		return true;
   1884 
   1885 	warn_assign(op, arg, ltp, lt, rtp, rt);
   1886 	return false;
   1887 }
   1888 
   1889 /* Prints a warning if a strange operator is used on an enum type. */
   1890 static void
   1891 check_bad_enum_operation(op_t op, const tnode_t *ln, const tnode_t *rn)
   1892 {
   1893 
   1894 	if (!eflag)
   1895 		return;
   1896 
   1897 	/*
   1898 	 * Enum as offset to a pointer is an exception (otherwise enums
   1899 	 * could not be used as array indices).
   1900 	 */
   1901 	if (op == PLUS &&
   1902 	    ((ln->tn_type->t_is_enum && rn->tn_type->t_tspec == PTR) ||
   1903 	     (rn->tn_type->t_is_enum && ln->tn_type->t_tspec == PTR))) {
   1904 		return;
   1905 	}
   1906 
   1907 	/* dubious operation on enum, op %s */
   1908 	warning(241, op_name(op));
   1909 }
   1910 
   1911 /*
   1912  * Prints a warning if an operator is applied to two different enum types.
   1913  */
   1914 static void
   1915 check_enum_type_mismatch(op_t op, int arg, const tnode_t *ln, const tnode_t *rn)
   1916 {
   1917 	const mod_t *mp;
   1918 
   1919 	mp = &modtab[op];
   1920 
   1921 	if (ln->tn_type->t_enum != rn->tn_type->t_enum) {
   1922 		switch (op) {
   1923 		case INIT:
   1924 			/* enum type mismatch between '%s' and '%s' in ... */
   1925 			warning(210,
   1926 			    type_name(ln->tn_type), type_name(rn->tn_type));
   1927 			break;
   1928 		case FARG:
   1929 			/* enum type mismatch, arg #%d (%s != %s) */
   1930 			warning(156, arg,
   1931 			    type_name(ln->tn_type), type_name(rn->tn_type));
   1932 			break;
   1933 		case RETURN:
   1934 			/* return value type mismatch (%s) and (%s) */
   1935 			warning(211,
   1936 			    type_name(ln->tn_type), type_name(rn->tn_type));
   1937 			break;
   1938 		default:
   1939 			/* enum type mismatch: '%s' '%s' '%s' */
   1940 			warning(130, type_name(ln->tn_type), mp->m_name,
   1941 			    type_name(rn->tn_type));
   1942 			break;
   1943 		}
   1944 	} else if (Pflag && mp->m_comparison && op != EQ && op != NE) {
   1945 		if (eflag)
   1946 			/* dubious comparison of enums, op %s */
   1947 			warning(243, mp->m_name);
   1948 	}
   1949 }
   1950 
   1951 /* Prints a warning if the operands mix between enum and integer. */
   1952 static void
   1953 check_enum_int_mismatch(op_t op, int arg, const tnode_t *ln, const tnode_t *rn)
   1954 {
   1955 
   1956 	if (!eflag)
   1957 		return;
   1958 
   1959 	switch (op) {
   1960 	case INIT:
   1961 		/*
   1962 		 * Initialization with 0 is allowed. Otherwise, all implicit
   1963 		 * initializations would need to be warned upon as well.
   1964 		 */
   1965 		if (!rn->tn_type->t_is_enum && rn->tn_op == CON &&
   1966 		    is_integer(rn->tn_type->t_tspec) &&
   1967 		    rn->tn_val->v_quad == 0) {
   1968 			return;
   1969 		}
   1970 		/* initialization of '%s' with '%s' */
   1971 		warning(277, type_name(ln->tn_type), type_name(rn->tn_type));
   1972 		break;
   1973 	case FARG:
   1974 		/* combination of '%s' and '%s', arg #%d */
   1975 		warning(278,
   1976 		    type_name(ln->tn_type), type_name(rn->tn_type), arg);
   1977 		break;
   1978 	case RETURN:
   1979 		/* combination of '%s' and '%s' in return */
   1980 		warning(279, type_name(ln->tn_type), type_name(rn->tn_type));
   1981 		break;
   1982 	default:
   1983 		/* combination of '%s' and '%s', op %s */
   1984 		warning(242, type_name(ln->tn_type), type_name(rn->tn_type),
   1985 		    op_name(op));
   1986 		break;
   1987 	}
   1988 }
   1989 
   1990 static void
   1991 check_enum_array_index(const tnode_t *ln, const tnode_t *rn)
   1992 {
   1993 	int max_array_index;
   1994 	int64_t max_enum_value;
   1995 	const struct sym *ec, *max_ec;
   1996 	const type_t *lt, *rt;
   1997 
   1998 	if (ln->tn_op != ADDR || ln->tn_left->tn_op != NAME)
   1999 		return;
   2000 
   2001 	lt = ln->tn_left->tn_type;
   2002 	if (lt->t_tspec != ARRAY || lt->t_incomplete_array)
   2003 		return;
   2004 
   2005 	if (rn->tn_op != CVT || !rn->tn_type->t_is_enum)
   2006 		return;
   2007 	if (rn->tn_left->tn_op != LOAD)
   2008 		return;
   2009 
   2010 	rt = rn->tn_left->tn_type;
   2011 	ec = rt->t_enum->en_first_enumerator;
   2012 	max_ec = ec;
   2013 	lint_assert(ec != NULL);
   2014 	for (ec = ec->s_next; ec != NULL; ec = ec->s_next)
   2015 		if (ec->u.s_enum_constant > max_ec->u.s_enum_constant)
   2016 			max_ec = ec;
   2017 
   2018 	max_enum_value = max_ec->u.s_enum_constant;
   2019 	lint_assert(INT_MIN <= max_enum_value && max_enum_value <= INT_MAX);
   2020 
   2021 	max_array_index = lt->t_dim - 1;
   2022 	if (max_enum_value == max_array_index)
   2023 		return;
   2024 
   2025 	/*
   2026 	 * If the largest enum constant is named '*_NUM_*', it is typically
   2027 	 * not part of the allowed enum values but a marker for the number
   2028 	 * of actual enum values.
   2029 	 */
   2030 	if (max_enum_value == max_array_index + 1 &&
   2031 	    (strstr(max_ec->s_name, "NUM") != NULL ||
   2032 	     strstr(max_ec->s_name, "num") != NULL))
   2033 		return;
   2034 
   2035 	/* maximum value %d of '%s' does not match maximum array index %d */
   2036 	warning(348, (int)max_enum_value, type_name(rt), max_array_index);
   2037 	print_previous_declaration(-1, max_ec);
   2038 }
   2039 
   2040 /*
   2041  * Build and initialize a new node.
   2042  */
   2043 static tnode_t *
   2044 new_tnode(op_t op, bool sys, type_t *type, tnode_t *ln, tnode_t *rn)
   2045 {
   2046 	tnode_t	*ntn;
   2047 	tspec_t	t;
   2048 #if 0 /* not yet */
   2049 	size_t l;
   2050 	uint64_t rnum;
   2051 #endif
   2052 
   2053 	ntn = expr_alloc_tnode();
   2054 
   2055 	ntn->tn_op = op;
   2056 	ntn->tn_type = type;
   2057 	ntn->tn_sys = sys;
   2058 	ntn->tn_left = ln;
   2059 	ntn->tn_right = rn;
   2060 
   2061 	switch (op) {
   2062 #if 0 /* not yet */
   2063 	case SHR:
   2064 		if (rn->tn_op != CON)
   2065 			break;
   2066 		rnum = rn->tn_val->v_quad;
   2067 		l = type_size_in_bits(ln->tn_type) / CHAR_SIZE;
   2068 		t = ln->tn_type->t_tspec;
   2069 		switch (l) {
   2070 		case 8:
   2071 			if (rnum >= 56)
   2072 				t = UCHAR;
   2073 			else if (rnum >= 48)
   2074 				t = USHORT;
   2075 			else if (rnum >= 32)
   2076 				t = UINT;
   2077 			break;
   2078 		case 4:
   2079 			if (rnum >= 24)
   2080 				t = UCHAR;
   2081 			else if (rnum >= 16)
   2082 				t = USHORT;
   2083 			break;
   2084 		case 2:
   2085 			if (rnum >= 8)
   2086 				t = UCHAR;
   2087 			break;
   2088 		default:
   2089 			break;
   2090 		}
   2091 		if (t != ln->tn_type->t_tspec)
   2092 			ntn->tn_type->t_tspec = t;
   2093 		break;
   2094 #endif
   2095 	case INDIR:
   2096 	case FSEL:
   2097 		lint_assert(ln->tn_type->t_tspec == PTR);
   2098 		t = ln->tn_type->t_subt->t_tspec;
   2099 		if (t != FUNC && t != VOID)
   2100 			ntn->tn_lvalue = true;
   2101 		break;
   2102 	default:
   2103 		break;
   2104 	}
   2105 
   2106 	return ntn;
   2107 }
   2108 
   2109 /*
   2110  * Performs the "integer promotions" (C99 6.3.1.1p2), which convert small
   2111  * integer types to either int or unsigned int.
   2112  *
   2113  * If allow_c90 is unset or the operand is a function argument with no type
   2114  * information (no prototype or variable # of args), converts float to double.
   2115  */
   2116 tnode_t *
   2117 promote(op_t op, bool farg, tnode_t *tn)
   2118 {
   2119 	tspec_t	t;
   2120 	type_t	*ntp;
   2121 	unsigned int len;
   2122 
   2123 	t = tn->tn_type->t_tspec;
   2124 
   2125 	if (!is_arithmetic(t))
   2126 		return tn;
   2127 
   2128 	if (allow_c90) {
   2129 		/*
   2130 		 * C99 6.3.1.1p2 requires for types with lower rank than int
   2131 		 * that "If an int can represent all the values of the
   2132 		 * original type, the value is converted to an int; otherwise
   2133 		 * it is converted to an unsigned int", and that "All other
   2134 		 * types are unchanged by the integer promotions".
   2135 		 */
   2136 		if (tn->tn_type->t_bitfield) {
   2137 			len = tn->tn_type->t_flen;
   2138 			if (len < size_in_bits(INT)) {
   2139 				t = INT;
   2140 			} else if (len == size_in_bits(INT)) {
   2141 				t = is_uinteger(t) ? UINT : INT;
   2142 			}
   2143 		} else if (t == CHAR || t == UCHAR || t == SCHAR) {
   2144 			t = (size_in_bits(CHAR) < size_in_bits(INT)
   2145 			     || t != UCHAR) ? INT : UINT;
   2146 		} else if (t == SHORT || t == USHORT) {
   2147 			t = (size_in_bits(SHORT) < size_in_bits(INT)
   2148 			     || t == SHORT) ? INT : UINT;
   2149 		} else if (t == ENUM) {
   2150 			t = INT;
   2151 		} else if (farg && t == FLOAT) {
   2152 			t = DOUBLE;
   2153 		}
   2154 	} else {
   2155 		/*
   2156 		 * In traditional C, keep unsigned and promote FLOAT
   2157 		 * to DOUBLE.
   2158 		 */
   2159 		if (t == UCHAR || t == USHORT) {
   2160 			t = UINT;
   2161 		} else if (t == CHAR || t == SCHAR || t == SHORT) {
   2162 			t = INT;
   2163 		} else if (t == FLOAT) {
   2164 			t = DOUBLE;
   2165 		} else if (t == ENUM) {
   2166 			t = INT;
   2167 		}
   2168 	}
   2169 
   2170 	if (t != tn->tn_type->t_tspec) {
   2171 		ntp = expr_dup_type(tn->tn_type);
   2172 		ntp->t_tspec = t;
   2173 		/*
   2174 		 * Keep t_is_enum even though t_tspec gets converted from
   2175 		 * ENUM to INT, so we are later able to check compatibility
   2176 		 * of enum types.
   2177 		 */
   2178 		tn = convert(op, 0, ntp, tn);
   2179 	}
   2180 
   2181 	return tn;
   2182 }
   2183 
   2184 /*
   2185  * Apply the "usual arithmetic conversions" (C99 6.3.1.8).
   2186  *
   2187  * This gives both operands the same type.
   2188  * This is done in different ways for traditional C and C90.
   2189  */
   2190 static void
   2191 balance(op_t op, tnode_t **lnp, tnode_t **rnp)
   2192 {
   2193 	tspec_t	lt, rt, t;
   2194 	int	i;
   2195 	bool	u;
   2196 	type_t	*ntp;
   2197 	static const tspec_t tl[] = {
   2198 		LDOUBLE, DOUBLE, FLOAT,
   2199 #ifdef INT128_SIZE
   2200 		UINT128, INT128,
   2201 #endif
   2202 		UQUAD, QUAD,
   2203 		ULONG, LONG,
   2204 		UINT, INT,
   2205 	};
   2206 
   2207 	lt = (*lnp)->tn_type->t_tspec;
   2208 	rt = (*rnp)->tn_type->t_tspec;
   2209 
   2210 	if (!is_arithmetic(lt) || !is_arithmetic(rt))
   2211 		return;
   2212 
   2213 	if (allow_c90) {
   2214 		if (lt == rt) {
   2215 			t = lt;
   2216 		} else if (lt == LCOMPLEX || rt == LCOMPLEX) {
   2217 			t = LCOMPLEX;
   2218 		} else if (lt == DCOMPLEX || rt == DCOMPLEX) {
   2219 			t = DCOMPLEX;
   2220 		} else if (lt == FCOMPLEX || rt == FCOMPLEX) {
   2221 			t = FCOMPLEX;
   2222 		} else if (lt == LDOUBLE || rt == LDOUBLE) {
   2223 			t = LDOUBLE;
   2224 		} else if (lt == DOUBLE || rt == DOUBLE) {
   2225 			t = DOUBLE;
   2226 		} else if (lt == FLOAT || rt == FLOAT) {
   2227 			t = FLOAT;
   2228 		} else {
   2229 			/*
   2230 			 * If type A has more bits than type B it should
   2231 			 * be able to hold all possible values of type B.
   2232 			 */
   2233 			if (size_in_bits(lt) > size_in_bits(rt)) {
   2234 				t = lt;
   2235 			} else if (size_in_bits(lt) < size_in_bits(rt)) {
   2236 				t = rt;
   2237 			} else {
   2238 				for (i = 3; tl[i] != INT; i++) {
   2239 					if (tl[i] == lt || tl[i] == rt)
   2240 						break;
   2241 				}
   2242 				if ((is_uinteger(lt) || is_uinteger(rt)) &&
   2243 				    !is_uinteger(tl[i])) {
   2244 					i--;
   2245 				}
   2246 				t = tl[i];
   2247 			}
   2248 		}
   2249 	} else {
   2250 		/* Keep unsigned in traditional C */
   2251 		u = is_uinteger(lt) || is_uinteger(rt);
   2252 		for (i = 0; tl[i] != INT; i++) {
   2253 			if (lt == tl[i] || rt == tl[i])
   2254 				break;
   2255 		}
   2256 		t = tl[i];
   2257 		if (u && is_integer(t) && !is_uinteger(t))
   2258 			t = unsigned_type(t);
   2259 	}
   2260 
   2261 	if (t != lt) {
   2262 		ntp = expr_dup_type((*lnp)->tn_type);
   2263 		ntp->t_tspec = t;
   2264 		*lnp = convert(op, 0, ntp, *lnp);
   2265 	}
   2266 	if (t != rt) {
   2267 		ntp = expr_dup_type((*rnp)->tn_type);
   2268 		ntp->t_tspec = t;
   2269 		*rnp = convert(op, 0, ntp, *rnp);
   2270 	}
   2271 }
   2272 
   2273 /*
   2274  * Insert a conversion operator, which converts the type of the node
   2275  * to another given type.
   2276  * If op is FARG, arg is the number of the argument (used for warnings).
   2277  */
   2278 tnode_t *
   2279 convert(op_t op, int arg, type_t *tp, tnode_t *tn)
   2280 {
   2281 	tnode_t	*ntn;
   2282 	tspec_t	nt, ot;
   2283 
   2284 	nt = tp->t_tspec;
   2285 	ot = tn->tn_type->t_tspec;
   2286 
   2287 	if (allow_trad && allow_c90 && op == FARG)
   2288 		check_prototype_conversion(arg, nt, ot, tp, tn);
   2289 
   2290 	if (is_integer(nt) && is_integer(ot)) {
   2291 		check_integer_conversion(op, arg, nt, ot, tp, tn);
   2292 	} else if (nt == PTR && is_null_pointer(tn)) {
   2293 		/* a null pointer may be assigned to any pointer. */
   2294 	} else if (is_integer(nt) && nt != BOOL && ot == PTR) {
   2295 		check_pointer_integer_conversion(op, nt, tp, tn);
   2296 	} else if (nt == PTR && ot == PTR && op == CVT) {
   2297 		check_pointer_conversion(tn, tp);
   2298 	}
   2299 
   2300 	ntn = expr_alloc_tnode();
   2301 	ntn->tn_op = CVT;
   2302 	ntn->tn_type = tp;
   2303 	ntn->tn_cast = op == CVT;
   2304 	ntn->tn_sys |= tn->tn_sys;
   2305 	ntn->tn_right = NULL;
   2306 	if (tn->tn_op != CON || nt == VOID) {
   2307 		ntn->tn_left = tn;
   2308 	} else {
   2309 		ntn->tn_op = CON;
   2310 		ntn->tn_val = expr_zero_alloc(sizeof(*ntn->tn_val));
   2311 		convert_constant(op, arg, ntn->tn_type, ntn->tn_val,
   2312 		    tn->tn_val);
   2313 	}
   2314 
   2315 	return ntn;
   2316 }
   2317 
   2318 static bool
   2319 should_warn_about_prototype_conversion(tspec_t nt,
   2320 				       tspec_t ot, const tnode_t *ptn)
   2321 {
   2322 
   2323 	if (nt == ot)
   2324 		return false;
   2325 
   2326 	if (nt == ENUM && ot == INT)
   2327 		return false;
   2328 
   2329 	if (is_floating(nt) != is_floating(ot) ||
   2330 	    portable_size_in_bits(nt) != portable_size_in_bits(ot)) {
   2331 		/* representation and/or width change */
   2332 		if (!is_integer(ot))
   2333 			return true;
   2334 		/*
   2335 		 * XXX: Investigate whether this rule makes sense; see
   2336 		 * tests/usr.bin/xlint/lint1/platform_long.c.
   2337 		 */
   2338 		return portable_size_in_bits(ot) > portable_size_in_bits(INT);
   2339 	}
   2340 
   2341 	if (!hflag)
   2342 		return false;
   2343 
   2344 	/*
   2345 	 * If the types differ only in sign and the argument has the same
   2346 	 * representation in both types, print no warning.
   2347 	 */
   2348 	if (ptn->tn_op == CON && is_integer(nt) &&
   2349 	    signed_type(nt) == signed_type(ot) &&
   2350 	    !msb(ptn->tn_val->v_quad, ot))
   2351 		return false;
   2352 
   2353 	return true;
   2354 }
   2355 
   2356 /*
   2357  * Warn if a prototype causes a type conversion that is different from what
   2358  * would happen to the same argument in the absence of a prototype.  This
   2359  * check is intended for code that needs to stay compatible with pre-C90 C.
   2360  *
   2361  * Errors/warnings about illegal type combinations are already printed
   2362  * in check_assign_types_compatible().
   2363  */
   2364 static void
   2365 check_prototype_conversion(int arg, tspec_t nt, tspec_t ot, type_t *tp,
   2366 			   tnode_t *tn)
   2367 {
   2368 	tnode_t	*ptn;
   2369 
   2370 	if (!is_arithmetic(nt) || !is_arithmetic(ot))
   2371 		return;
   2372 
   2373 	/*
   2374 	 * If the type of the formal parameter is char/short, a warning
   2375 	 * would be useless, because functions declared the old style
   2376 	 * can't expect char/short arguments.
   2377 	 */
   2378 	if (nt == CHAR || nt == SCHAR || nt == UCHAR ||
   2379 	    nt == SHORT || nt == USHORT)
   2380 		return;
   2381 
   2382 	/* apply the default promotion */
   2383 	ptn = promote(NOOP, true, tn);
   2384 	ot = ptn->tn_type->t_tspec;
   2385 
   2386 	if (should_warn_about_prototype_conversion(nt, ot, ptn)) {
   2387 		/* argument #%d is converted from '%s' to '%s' ... */
   2388 		warning(259, arg, type_name(tn->tn_type), type_name(tp));
   2389 	}
   2390 }
   2391 
   2392 /*
   2393  * When converting a large integer type to a small integer type, in some
   2394  * cases the value of the actual expression is further restricted than the
   2395  * type bounds, such as in (expr & 0xFF) or (expr % 100) or (expr >> 24).
   2396  *
   2397  * See new_tnode, the '#if 0' code for SHR.
   2398  */
   2399 static bool
   2400 can_represent(const type_t *tp, const tnode_t *tn)
   2401 {
   2402 
   2403 	debug_step("%s: type '%s'", __func__, type_name(tp));
   2404 	debug_node(tn);
   2405 
   2406 	uint64_t nmask = value_bits(ic_length_in_bits(tp));
   2407 	if (!is_uinteger(tp->t_tspec))
   2408 		nmask >>= 1;
   2409 
   2410 	integer_constraints c = ic_expr(tn);
   2411 	if ((~c.bclr & ~nmask) == 0)
   2412 		return true;
   2413 
   2414 	return false;
   2415 }
   2416 
   2417 /*
   2418  * Print warnings for conversions of integer types which may cause problems.
   2419  */
   2420 static void
   2421 check_integer_conversion(op_t op, int arg, tspec_t nt, tspec_t ot, type_t *tp,
   2422 			 tnode_t *tn)
   2423 {
   2424 
   2425 	if (tn->tn_op == CON)
   2426 		return;
   2427 
   2428 	if (op == CVT)
   2429 		return;
   2430 
   2431 	if (allow_c99 && nt == BOOL)
   2432 		return;		/* See C99 6.3.1.2 */
   2433 
   2434 	if (Pflag && pflag && aflag > 0 &&
   2435 	    portable_size_in_bits(nt) > portable_size_in_bits(ot) &&
   2436 	    is_uinteger(nt) != is_uinteger(ot)) {
   2437 		if (op == FARG) {
   2438 			/* conversion to '%s' may sign-extend ... */
   2439 			warning(297, type_name(tp), arg);
   2440 		} else {
   2441 			/* conversion to '%s' may sign-extend ... */
   2442 			warning(131, type_name(tp));
   2443 		}
   2444 	}
   2445 
   2446 	if (Pflag && portable_size_in_bits(nt) > portable_size_in_bits(ot) &&
   2447 	    (tn->tn_op == PLUS || tn->tn_op == MINUS || tn->tn_op == MULT ||
   2448 	     tn->tn_op == SHL)) {
   2449 		/* suggest cast from '%s' to '%s' on op %s to ... */
   2450 		warning(324, type_name(gettyp(ot)), type_name(tp),
   2451 		    op_name(tn->tn_op));
   2452 	}
   2453 
   2454 	if (aflag > 0 &&
   2455 	    portable_size_in_bits(nt) < portable_size_in_bits(ot) &&
   2456 	    (ot == LONG || ot == ULONG || ot == QUAD || ot == UQUAD ||
   2457 	     aflag > 1) &&
   2458 	    !can_represent(tp, tn)) {
   2459 		if (op == FARG) {
   2460 			/* conversion from '%s' to '%s' may lose ... */
   2461 			warning(298,
   2462 			    type_name(tn->tn_type), type_name(tp), arg);
   2463 		} else {
   2464 			/* conversion from '%s' to '%s' may lose accuracy */
   2465 			warning(132,
   2466 			    type_name(tn->tn_type), type_name(tp));
   2467 		}
   2468 	}
   2469 }
   2470 
   2471 /*
   2472  * Print warnings for dubious conversions of pointer to integer.
   2473  */
   2474 static void
   2475 check_pointer_integer_conversion(op_t op, tspec_t nt, type_t *tp, tnode_t *tn)
   2476 {
   2477 
   2478 	if (tn->tn_op == CON)
   2479 		return;
   2480 	if (op != CVT)
   2481 		return;		/* We got already an error. */
   2482 	if (portable_size_in_bits(nt) >= portable_size_in_bits(PTR))
   2483 		return;
   2484 
   2485 	if (pflag && size_in_bits(nt) >= size_in_bits(PTR)) {
   2486 		/* conversion of pointer to '%s' may lose bits */
   2487 		warning(134, type_name(tp));
   2488 	} else {
   2489 		/* conversion of pointer to '%s' loses bits */
   2490 		warning(133, type_name(tp));
   2491 	}
   2492 }
   2493 
   2494 static bool
   2495 should_warn_about_pointer_cast(const type_t *nstp, tspec_t nst,
   2496 			       const type_t *ostp, tspec_t ost)
   2497 {
   2498 	/*
   2499 	 * Casting a pointer to 'struct S' to a pointer to another struct that
   2500 	 * has 'struct S' as its first member is ok, see msg_247.c, 'struct
   2501 	 * counter'.
   2502 	 */
   2503 	if (nst == STRUCT && ost == STRUCT &&
   2504 	    nstp->t_str->sou_first_member != NULL &&
   2505 	    nstp->t_str->sou_first_member->s_type == ostp)
   2506 		return false;
   2507 
   2508 	if (is_incomplete(nstp) || is_incomplete(ostp))
   2509 		return false;
   2510 
   2511 	if (is_struct_or_union(nst) && nstp->t_str != ostp->t_str)
   2512 		return true;
   2513 
   2514 	if (nst == CHAR || nst == UCHAR)
   2515 		return false;	/* for the sake of traditional C code */
   2516 	if (ost == CHAR || ost == UCHAR)
   2517 		return false;	/* for the sake of traditional C code */
   2518 
   2519 	return portable_size_in_bits(nst) != portable_size_in_bits(ost);
   2520 }
   2521 
   2522 /*
   2523  * Warn about questionable pointer conversions.
   2524  */
   2525 static void
   2526 check_pointer_conversion(tnode_t *tn, type_t *ntp)
   2527 {
   2528 	const type_t *nstp, *otp, *ostp;
   2529 	tspec_t nst, ost;
   2530 	const char *nts, *ots;
   2531 
   2532 	nstp = ntp->t_subt;
   2533 	otp = tn->tn_type;
   2534 	ostp = otp->t_subt;
   2535 	nst = nstp->t_tspec;
   2536 	ost = ostp->t_tspec;
   2537 
   2538 	if (nst == VOID || ost == VOID) {
   2539 		/* TODO: C99 behaves like C90 here. */
   2540 		if ((!allow_trad && !allow_c99) && (nst == FUNC || ost == FUNC)) {
   2541 			/* null pointers are already handled in convert() */
   2542 			*(nst == FUNC ? &nts : &ots) = "function pointer";
   2543 			*(nst == VOID ? &nts : &ots) = "'void *'";
   2544 			/* ANSI C forbids conversion of %s to %s */
   2545 			warning(303, ots, nts);
   2546 		}
   2547 		return;
   2548 	} else if (nst == FUNC && ost == FUNC) {
   2549 		return;
   2550 	} else if (nst == FUNC || ost == FUNC) {
   2551 		/* converting '%s' to '%s' is questionable */
   2552 		warning(229, type_name(otp), type_name(ntp));
   2553 		return;
   2554 	}
   2555 
   2556 	if (hflag && alignment_in_bits(nstp) > alignment_in_bits(ostp) &&
   2557 	    ost != CHAR && ost != UCHAR &&
   2558 	    !is_incomplete(ostp)) {
   2559 		/* converting '%s' to '%s' may cause alignment problem */
   2560 		warning(135, type_name(otp), type_name(ntp));
   2561 	}
   2562 
   2563 	if (cflag && should_warn_about_pointer_cast(nstp, nst, ostp, ost)) {
   2564 		/* pointer cast from '%s' to '%s' may be troublesome */
   2565 		warning(247, type_name(otp), type_name(ntp));
   2566 	}
   2567 }
   2568 
   2569 static void
   2570 convert_constant_floating(op_t op, int arg, tspec_t ot, const type_t *tp,
   2571 			  tspec_t nt, val_t *v, val_t *nv)
   2572 {
   2573 	ldbl_t	max = 0.0, min = 0.0;
   2574 
   2575 	switch (nt) {
   2576 	case CHAR:
   2577 		max = TARG_CHAR_MAX;	min = TARG_CHAR_MIN;	break;
   2578 	case UCHAR:
   2579 		max = TARG_UCHAR_MAX;	min = 0;		break;
   2580 	case SCHAR:
   2581 		max = TARG_SCHAR_MAX;	min = TARG_SCHAR_MIN;	break;
   2582 	case SHORT:
   2583 		max = TARG_SHRT_MAX;	min = TARG_SHRT_MIN;	break;
   2584 	case USHORT:
   2585 		max = TARG_USHRT_MAX;	min = 0;		break;
   2586 	case ENUM:
   2587 	case INT:
   2588 		max = TARG_INT_MAX;	min = TARG_INT_MIN;	break;
   2589 	case UINT:
   2590 		max = TARG_UINT_MAX;	min = 0;		break;
   2591 	case LONG:
   2592 		max = TARG_LONG_MAX;	min = TARG_LONG_MIN;	break;
   2593 	case ULONG:
   2594 		max = TARG_ULONG_MAX;	min = 0;		break;
   2595 	case QUAD:
   2596 		max = QUAD_MAX;		min = QUAD_MIN;		break;
   2597 	case UQUAD:
   2598 		max = UQUAD_MAX;	min = 0;		break;
   2599 	case FLOAT:
   2600 	case FCOMPLEX:
   2601 		max = FLT_MAX;		min = -FLT_MAX;		break;
   2602 	case DOUBLE:
   2603 	case DCOMPLEX:
   2604 		max = DBL_MAX;		min = -DBL_MAX;		break;
   2605 	case PTR:
   2606 		/* Got already an error because of float --> ptr */
   2607 	case LDOUBLE:
   2608 	case LCOMPLEX:
   2609 		/* LINTED 248 */
   2610 		max = LDBL_MAX;		min = -max;		break;
   2611 	default:
   2612 		lint_assert(/*CONSTCOND*/false);
   2613 	}
   2614 	if (v->v_ldbl > max || v->v_ldbl < min) {
   2615 		lint_assert(nt != LDOUBLE);
   2616 		if (op == FARG) {
   2617 			/* conversion of '%s' to '%s' is out of range, ... */
   2618 			warning(295,
   2619 			    type_name(gettyp(ot)), type_name(tp), arg);
   2620 		} else {
   2621 			/* conversion of '%s' to '%s' is out of range */
   2622 			warning(119,
   2623 			    type_name(gettyp(ot)), type_name(tp));
   2624 		}
   2625 		v->v_ldbl = v->v_ldbl > 0 ? max : min;
   2626 	}
   2627 
   2628 	if (nt == FLOAT) {
   2629 		nv->v_ldbl = (float)v->v_ldbl;
   2630 	} else if (nt == DOUBLE) {
   2631 		nv->v_ldbl = (double)v->v_ldbl;
   2632 	} else if (nt == LDOUBLE) {
   2633 		nv->v_ldbl = v->v_ldbl;
   2634 	} else {
   2635 		nv->v_quad = (int64_t)v->v_ldbl;
   2636 	}
   2637 }
   2638 
   2639 static bool
   2640 convert_constant_to_floating(tspec_t nt, val_t *nv,
   2641 			     tspec_t ot, const val_t *v)
   2642 {
   2643 	if (nt == FLOAT) {
   2644 		nv->v_ldbl = (ot == PTR || is_uinteger(ot)) ?
   2645 		    (float)(uint64_t)v->v_quad : (float)v->v_quad;
   2646 	} else if (nt == DOUBLE) {
   2647 		nv->v_ldbl = (ot == PTR || is_uinteger(ot)) ?
   2648 		    (double)(uint64_t)v->v_quad : (double)v->v_quad;
   2649 	} else if (nt == LDOUBLE) {
   2650 		nv->v_ldbl = (ot == PTR || is_uinteger(ot)) ?
   2651 		    (ldbl_t)(uint64_t)v->v_quad : (ldbl_t)v->v_quad;
   2652 	} else
   2653 		return false;
   2654 	return true;
   2655 }
   2656 
   2657 /*
   2658  * Print a warning if bits which were set are lost due to the conversion.
   2659  * This can happen with operator ORASS only.
   2660  */
   2661 static void
   2662 convert_constant_check_range_bitor(size_t nsz, size_t osz, const val_t *v,
   2663 				   uint64_t xmask, op_t op)
   2664 {
   2665 	if (nsz < osz && (v->v_quad & xmask) != 0) {
   2666 		/* constant truncated by conversion, op %s */
   2667 		warning(306, op_name(op));
   2668 	}
   2669 }
   2670 
   2671 /*
   2672  * Print a warning if additional bits are not all 1
   2673  * and the most significant bit of the old value is 1,
   2674  * or if at least one (but not all) removed bit was 0.
   2675  */
   2676 static void
   2677 convert_constant_check_range_bitand(size_t nsz, size_t osz,
   2678 				    uint64_t xmask, const val_t *nv,
   2679 				    tspec_t ot, const val_t *v,
   2680 				    const type_t *tp, op_t op)
   2681 {
   2682 	if (nsz > osz &&
   2683 	    (nv->v_quad & bit((unsigned int)(osz - 1))) != 0 &&
   2684 	    (nv->v_quad & xmask) != xmask) {
   2685 		/* extra bits set to 0 in conversion of '%s' to '%s', ... */
   2686 		warning(309, type_name(gettyp(ot)),
   2687 		    type_name(tp), op_name(op));
   2688 	} else if (nsz < osz &&
   2689 		   (v->v_quad & xmask) != xmask &&
   2690 		   (v->v_quad & xmask) != 0) {
   2691 		/* constant truncated by conversion, op %s */
   2692 		warning(306, op_name(op));
   2693 	}
   2694 }
   2695 
   2696 static void
   2697 convert_constant_check_range_signed(op_t op, int arg)
   2698 {
   2699 	if (op == ASSIGN) {
   2700 		/* assignment of negative constant to unsigned type */
   2701 		warning(164);
   2702 	} else if (op == INIT) {
   2703 		/* initialization of unsigned with negative constant */
   2704 		warning(221);
   2705 	} else if (op == FARG) {
   2706 		/* conversion of negative constant to unsigned type, ... */
   2707 		warning(296, arg);
   2708 	} else if (modtab[op].m_comparison) {
   2709 		/* handled by check_integer_comparison() */
   2710 	} else {
   2711 		/* conversion of negative constant to unsigned type */
   2712 		warning(222);
   2713 	}
   2714 }
   2715 
   2716 /*
   2717  * Loss of significant bit(s). All truncated bits
   2718  * of unsigned types or all truncated bits plus the
   2719  * msb of the target for signed types are considered
   2720  * to be significant bits. Loss of significant bits
   2721  * means that at least one of the bits was set in an
   2722  * unsigned type or that at least one but not all of
   2723  * the bits was set in a signed type.
   2724  * Loss of significant bits means that it is not
   2725  * possible, also not with necessary casts, to convert
   2726  * back to the original type. A example for a
   2727  * necessary cast is:
   2728  *	char c;	int	i; c = 128;
   2729  *	i = c;			** yields -128 **
   2730  *	i = (unsigned char)c;	** yields 128 **
   2731  */
   2732 static void
   2733 convert_constant_check_range_truncated(op_t op, int arg, const type_t *tp,
   2734 				       tspec_t ot)
   2735 {
   2736 	if (op == ASSIGN && tp->t_bitfield) {
   2737 		/* precision lost in bit-field assignment */
   2738 		warning(166);
   2739 	} else if (op == ASSIGN) {
   2740 		/* constant truncated by assignment */
   2741 		warning(165);
   2742 	} else if (op == INIT && tp->t_bitfield) {
   2743 		/* bit-field initializer does not fit */
   2744 		warning(180);
   2745 	} else if (op == INIT) {
   2746 		/* initializer does not fit */
   2747 		warning(178);
   2748 	} else if (op == CASE) {
   2749 		/* case label affected by conversion */
   2750 		warning(196);
   2751 	} else if (op == FARG) {
   2752 		/* conversion of '%s' to '%s' is out of range, arg #%d */
   2753 		warning(295,
   2754 		    type_name(gettyp(ot)), type_name(tp), arg);
   2755 	} else {
   2756 		/* conversion of '%s' to '%s' is out of range */
   2757 		warning(119,
   2758 		    type_name(gettyp(ot)), type_name(tp));
   2759 	}
   2760 }
   2761 
   2762 static void
   2763 convert_constant_check_range_loss(op_t op, int arg, const type_t *tp,
   2764 				  tspec_t ot)
   2765 {
   2766 	if (op == ASSIGN && tp->t_bitfield) {
   2767 		/* precision lost in bit-field assignment */
   2768 		warning(166);
   2769 	} else if (op == INIT && tp->t_bitfield) {
   2770 		/* bit-field initializer out of range */
   2771 		warning(11);
   2772 	} else if (op == CASE) {
   2773 		/* case label affected by conversion */
   2774 		warning(196);
   2775 	} else if (op == FARG) {
   2776 		/* conversion of '%s' to '%s' is out of range, arg #%d */
   2777 		warning(295,
   2778 		    type_name(gettyp(ot)), type_name(tp), arg);
   2779 	} else {
   2780 		/* conversion of '%s' to '%s' is out of range */
   2781 		warning(119,
   2782 		    type_name(gettyp(ot)), type_name(tp));
   2783 	}
   2784 }
   2785 
   2786 static void
   2787 convert_constant_check_range(tspec_t ot, const type_t *tp, tspec_t nt,
   2788 			     op_t op, int arg, const val_t *v, val_t *nv)
   2789 {
   2790 	unsigned int osz, nsz;
   2791 	uint64_t xmask, xmsk1;
   2792 
   2793 	osz = size_in_bits(ot);
   2794 	nsz = tp->t_bitfield ? tp->t_flen : size_in_bits(nt);
   2795 	xmask = value_bits(nsz) ^ value_bits(osz);
   2796 	xmsk1 = value_bits(nsz) ^ value_bits(osz - 1);
   2797 	/*
   2798 	 * For bitwise operations we are not interested in the
   2799 	 * value, but in the bits itself.
   2800 	 */
   2801 	if (op == ORASS || op == BITOR || op == BITXOR) {
   2802 		convert_constant_check_range_bitor(nsz, osz, v, xmask, op);
   2803 	} else if (op == ANDASS || op == BITAND) {
   2804 		convert_constant_check_range_bitand(nsz, osz, xmask, nv, ot,
   2805 		    v, tp, op);
   2806 	} else if ((nt != PTR && is_uinteger(nt)) &&
   2807 		   (ot != PTR && !is_uinteger(ot)) &&
   2808 		   v->v_quad < 0) {
   2809 		convert_constant_check_range_signed(op, arg);
   2810 	} else if (nv->v_quad != v->v_quad && nsz <= osz &&
   2811 		   (v->v_quad & xmask) != 0 &&
   2812 		   (is_uinteger(ot) || (v->v_quad & xmsk1) != xmsk1)) {
   2813 		convert_constant_check_range_truncated(op, arg, tp, ot);
   2814 	} else if (nv->v_quad != v->v_quad) {
   2815 		convert_constant_check_range_loss(op, arg, tp, ot);
   2816 	}
   2817 }
   2818 
   2819 /*
   2820  * Converts a typed constant to a constant of another type.
   2821  *
   2822  * op		operator which requires conversion
   2823  * arg		if op is FARG, # of argument
   2824  * tp		type in which to convert the constant
   2825  * nv		new constant
   2826  * v		old constant
   2827  */
   2828 void
   2829 convert_constant(op_t op, int arg, const type_t *tp, val_t *nv, val_t *v)
   2830 {
   2831 	tspec_t ot, nt;
   2832 	unsigned int sz;
   2833 	bool range_check;
   2834 
   2835 	/*
   2836 	 * TODO: make 'v' const; the name of this function does not suggest
   2837 	 *  that it modifies 'v'.
   2838 	 */
   2839 	ot = v->v_tspec;
   2840 	nt = nv->v_tspec = tp->t_tspec;
   2841 	range_check = false;
   2842 
   2843 	if (nt == BOOL) {	/* C99 6.3.1.2 */
   2844 		nv->v_unsigned_since_c90 = false;
   2845 		nv->v_quad = is_nonzero_val(v) ? 1 : 0;
   2846 		return;
   2847 	}
   2848 
   2849 	if (ot == FLOAT || ot == DOUBLE || ot == LDOUBLE) {
   2850 		convert_constant_floating(op, arg, ot, tp, nt, v, nv);
   2851 	} else if (!convert_constant_to_floating(nt, nv, ot, v)) {
   2852 		range_check = true;	/* Check for lost precision. */
   2853 		nv->v_quad = v->v_quad;
   2854 	}
   2855 
   2856 	if (allow_trad && allow_c90 && v->v_unsigned_since_c90 &&
   2857 	    (is_floating(nt) || (
   2858 		(is_integer(nt) && !is_uinteger(nt) &&
   2859 		 portable_size_in_bits(nt) > portable_size_in_bits(ot))))) {
   2860 		/* ANSI C treats constant as unsigned */
   2861 		warning(157);
   2862 		v->v_unsigned_since_c90 = false;
   2863 	}
   2864 
   2865 	if (is_integer(nt)) {
   2866 		sz = tp->t_bitfield ? tp->t_flen : size_in_bits(nt);
   2867 		nv->v_quad = convert_integer(nv->v_quad, nt, sz);
   2868 	}
   2869 
   2870 	if (range_check && op != CVT)
   2871 		convert_constant_check_range(ot, tp, nt, op, arg, v, nv);
   2872 }
   2873 
   2874 /*
   2875  * Called if incompatible types were detected.
   2876  * Prints a appropriate warning.
   2877  */
   2878 static void
   2879 warn_incompatible_types(op_t op,
   2880 			const type_t *ltp, tspec_t lt,
   2881 			const type_t *rtp, tspec_t rt)
   2882 {
   2883 	const mod_t *mp;
   2884 
   2885 	mp = &modtab[op];
   2886 
   2887 	if (lt == VOID || (mp->m_binary && rt == VOID)) {
   2888 		/* void type illegal in expression */
   2889 		error(109);
   2890 	} else if (op == ASSIGN) {
   2891 		if (is_struct_or_union(lt) && is_struct_or_union(rt)) {
   2892 			/* assignment of different structures (%s != %s) */
   2893 			error(240, tspec_name(lt), tspec_name(rt));
   2894 		} else {
   2895 			/* cannot assign to '%s' from '%s' */
   2896 			error(171, type_name(ltp), type_name(rtp));
   2897 		}
   2898 	} else if (mp->m_binary) {
   2899 		/* operands of '%s' have incompatible types '%s' and '%s' */
   2900 		error(107, mp->m_name, tspec_name(lt), tspec_name(rt));
   2901 	} else {
   2902 		lint_assert(rt == NOTSPEC);
   2903 		/* operand of '%s' has invalid type '%s' */
   2904 		error(108, mp->m_name, type_name(ltp));
   2905 	}
   2906 }
   2907 
   2908 /*
   2909  * Called if incompatible pointer types are detected.
   2910  * Print an appropriate warning.
   2911  */
   2912 static void
   2913 warn_incompatible_pointers(const mod_t *mp,
   2914 			   const type_t *ltp, const type_t *rtp)
   2915 {
   2916 	tspec_t	lt, rt;
   2917 
   2918 	lint_assert(ltp->t_tspec == PTR);
   2919 	lint_assert(rtp->t_tspec == PTR);
   2920 
   2921 	lt = ltp->t_subt->t_tspec;
   2922 	rt = rtp->t_subt->t_tspec;
   2923 
   2924 	if (is_struct_or_union(lt) && is_struct_or_union(rt)) {
   2925 		if (mp == NULL) {
   2926 			/* illegal structure pointer combination */
   2927 			warning(244);
   2928 		} else {
   2929 			/* incompatible structure pointers: '%s' '%s' '%s' */
   2930 			warning(245, type_name(ltp), mp->m_name, type_name(rtp));
   2931 		}
   2932 	} else {
   2933 		if (mp == NULL) {
   2934 			/* illegal combination of '%s' and '%s' */
   2935 			warning(184, type_name(ltp), type_name(rtp));
   2936 		} else {
   2937 			/* illegal combination of '%s' and '%s', op '%s' */
   2938 			warning(124,
   2939 			    type_name(ltp), type_name(rtp), mp->m_name);
   2940 		}
   2941 	}
   2942 }
   2943 
   2944 /* Return a type based on tp1, with added qualifiers from tp2. */
   2945 static type_t *
   2946 merge_qualifiers(type_t *tp1, const type_t *tp2)
   2947 {
   2948 	type_t *ntp, *nstp;
   2949 	bool c1, c2, v1, v2;
   2950 
   2951 	lint_assert(tp1->t_tspec == PTR);
   2952 	lint_assert(tp2->t_tspec == PTR);
   2953 
   2954 	c1 = tp1->t_subt->t_const;
   2955 	c2 = tp2->t_subt->t_const;
   2956 	v1 = tp1->t_subt->t_volatile;
   2957 	v2 = tp2->t_subt->t_volatile;
   2958 
   2959 	if (c1 == (c1 | c2) && v1 == (v1 | v2))
   2960 		return tp1;
   2961 
   2962 	nstp = expr_dup_type(tp1->t_subt);
   2963 	nstp->t_const |= c2;
   2964 	nstp->t_volatile |= v2;
   2965 
   2966 	ntp = expr_dup_type(tp1);
   2967 	ntp->t_subt = nstp;
   2968 	return ntp;
   2969 }
   2970 
   2971 /*
   2972  * Returns true if the given structure or union has a constant member
   2973  * (maybe recursively).
   2974  */
   2975 static bool
   2976 has_constant_member(const type_t *tp)
   2977 {
   2978 	sym_t *m;
   2979 
   2980 	lint_assert(is_struct_or_union(tp->t_tspec));
   2981 
   2982 	for (m = tp->t_str->sou_first_member; m != NULL; m = m->s_next) {
   2983 		const type_t *mtp = m->s_type;
   2984 		if (mtp->t_const)
   2985 			return true;
   2986 		if (is_struct_or_union(mtp->t_tspec) &&
   2987 		    has_constant_member(mtp))
   2988 			return true;
   2989 	}
   2990 	return false;
   2991 }
   2992 
   2993 /*
   2994  * Create a new node for one of the operators POINT and ARROW.
   2995  */
   2996 static tnode_t *
   2997 build_struct_access(op_t op, bool sys, tnode_t *ln, tnode_t *rn)
   2998 {
   2999 	tnode_t	*ntn, *ctn;
   3000 	bool	nolval;
   3001 
   3002 	lint_assert(rn->tn_op == NAME);
   3003 	lint_assert(is_member(rn->tn_sym));
   3004 
   3005 	/*
   3006 	 * Remember if the left operand is an lvalue (structure members
   3007 	 * are lvalues if and only if the structure itself is an lvalue).
   3008 	 */
   3009 	nolval = op == POINT && !ln->tn_lvalue;
   3010 
   3011 	if (op == POINT) {
   3012 		ln = build_address(sys, ln, true);
   3013 	} else if (ln->tn_type->t_tspec != PTR) {
   3014 		lint_assert(!allow_c90);
   3015 		lint_assert(is_integer(ln->tn_type->t_tspec));
   3016 		ln = convert(NOOP, 0, expr_derive_type(gettyp(VOID), PTR), ln);
   3017 	}
   3018 
   3019 	ctn = build_integer_constant(PTRDIFF_TSPEC,
   3020 	    rn->tn_sym->u.s_member.sm_offset_in_bits / CHAR_SIZE);
   3021 
   3022 	ntn = new_tnode(PLUS, sys, expr_derive_type(rn->tn_type, PTR),
   3023 	    ln, ctn);
   3024 	if (ln->tn_op == CON)
   3025 		ntn = fold(ntn);
   3026 
   3027 	if (rn->tn_type->t_bitfield) {
   3028 		ntn = new_tnode(FSEL, sys, ntn->tn_type->t_subt, ntn, NULL);
   3029 	} else {
   3030 		ntn = new_tnode(INDIR, sys, ntn->tn_type->t_subt, ntn, NULL);
   3031 	}
   3032 
   3033 	if (nolval)
   3034 		ntn->tn_lvalue = false;
   3035 
   3036 	return ntn;
   3037 }
   3038 
   3039 /*
   3040  * Create a node for INCAFT, INCBEF, DECAFT and DECBEF.
   3041  */
   3042 static tnode_t *
   3043 build_prepost_incdec(op_t op, bool sys, tnode_t *ln)
   3044 {
   3045 	tnode_t	*cn, *ntn;
   3046 
   3047 	lint_assert(ln != NULL);
   3048 
   3049 	if (ln->tn_type->t_tspec == PTR) {
   3050 		cn = subt_size_in_bytes(ln->tn_type);
   3051 	} else {
   3052 		cn = build_integer_constant(INT, (int64_t)1);
   3053 	}
   3054 	ntn = new_tnode(op, sys, ln->tn_type, ln, cn);
   3055 
   3056 	return ntn;
   3057 }
   3058 
   3059 /*
   3060  * Create a node for REAL, IMAG
   3061  */
   3062 static tnode_t *
   3063 build_real_imag(op_t op, bool sys, tnode_t *ln)
   3064 {
   3065 	tnode_t	*cn, *ntn;
   3066 
   3067 	lint_assert(ln != NULL);
   3068 
   3069 	if (ln->tn_op == NAME) {
   3070 		/*
   3071 		 * This may be too much, but it avoids wrong warnings.
   3072 		 * See d_c99_complex_split.c.
   3073 		 */
   3074 		mark_as_used(ln->tn_sym, false, false);
   3075 		mark_as_set(ln->tn_sym);
   3076 	}
   3077 
   3078 	switch (ln->tn_type->t_tspec) {
   3079 	case LCOMPLEX:
   3080 		/* XXX: integer and LDOUBLE don't match. */
   3081 		cn = build_integer_constant(LDOUBLE, (int64_t)1);
   3082 		break;
   3083 	case DCOMPLEX:
   3084 		/* XXX: integer and DOUBLE don't match. */
   3085 		cn = build_integer_constant(DOUBLE, (int64_t)1);
   3086 		break;
   3087 	case FCOMPLEX:
   3088 		/* XXX: integer and FLOAT don't match. */
   3089 		cn = build_integer_constant(FLOAT, (int64_t)1);
   3090 		break;
   3091 	default:
   3092 		/* __%s__ is illegal for type %s */
   3093 		error(276, op == REAL ? "real" : "imag",
   3094 		    type_name(ln->tn_type));
   3095 		return NULL;
   3096 	}
   3097 	ntn = new_tnode(op, sys, cn->tn_type, ln, cn);
   3098 	ntn->tn_lvalue = true;
   3099 
   3100 	return ntn;
   3101 }
   3102 
   3103 /*
   3104  * Create a tree node for the unary & operator
   3105  */
   3106 static tnode_t *
   3107 build_address(bool sys, tnode_t *tn, bool noign)
   3108 {
   3109 	tspec_t	t;
   3110 
   3111 	if (!noign && ((t = tn->tn_type->t_tspec) == ARRAY || t == FUNC)) {
   3112 		if (!allow_c90)
   3113 			/* '&' before array or function: ignored */
   3114 			warning(127);
   3115 		return tn;
   3116 	}
   3117 
   3118 	/* eliminate &* */
   3119 	if (tn->tn_op == INDIR &&
   3120 	    tn->tn_left->tn_type->t_tspec == PTR &&
   3121 	    tn->tn_left->tn_type->t_subt == tn->tn_type) {
   3122 		return tn->tn_left;
   3123 	}
   3124 
   3125 	return new_tnode(ADDR, sys, expr_derive_type(tn->tn_type, PTR),
   3126 	    tn, NULL);
   3127 }
   3128 
   3129 /*
   3130  * Create a node for operators PLUS and MINUS.
   3131  */
   3132 static tnode_t *
   3133 build_plus_minus(op_t op, bool sys, tnode_t *ln, tnode_t *rn)
   3134 {
   3135 
   3136 	/* If pointer and integer, then pointer to the lhs. */
   3137 	if (rn->tn_type->t_tspec == PTR && is_integer(ln->tn_type->t_tspec)) {
   3138 		tnode_t *tmp = ln;
   3139 		ln = rn;
   3140 		rn = tmp;
   3141 	}
   3142 
   3143 	/* pointer +- integer */
   3144 	if (ln->tn_type->t_tspec == PTR && rn->tn_type->t_tspec != PTR) {
   3145 		lint_assert(is_integer(rn->tn_type->t_tspec));
   3146 
   3147 		check_ctype_macro_invocation(ln, rn);
   3148 		check_enum_array_index(ln, rn);
   3149 
   3150 		tnode_t *elsz = subt_size_in_bytes(ln->tn_type);
   3151 		if (rn->tn_type->t_tspec != elsz->tn_type->t_tspec)
   3152 			rn = convert(NOOP, 0, elsz->tn_type, rn);
   3153 
   3154 		tnode_t *prod = new_tnode(MULT, sys, rn->tn_type, rn, elsz);
   3155 		if (rn->tn_op == CON)
   3156 			prod = fold(prod);
   3157 
   3158 		return new_tnode(op, sys, ln->tn_type, ln, prod);
   3159 	}
   3160 
   3161 	/* pointer - pointer */
   3162 	if (rn->tn_type->t_tspec == PTR) {
   3163 		lint_assert(ln->tn_type->t_tspec == PTR);
   3164 		lint_assert(op == MINUS);
   3165 
   3166 		type_t *ptrdiff = gettyp(PTRDIFF_TSPEC);
   3167 		tnode_t *raw_diff = new_tnode(op, sys, ptrdiff, ln, rn);
   3168 		if (ln->tn_op == CON && rn->tn_op == CON)
   3169 			raw_diff = fold(raw_diff);
   3170 
   3171 		tnode_t *elsz = subt_size_in_bytes(ln->tn_type);
   3172 		balance(NOOP, &raw_diff, &elsz);
   3173 
   3174 		return new_tnode(DIV, sys, ptrdiff, raw_diff, elsz);
   3175 	}
   3176 
   3177 	return new_tnode(op, sys, ln->tn_type, ln, rn);
   3178 }
   3179 
   3180 /*
   3181  * Create a node for operators SHL and SHR.
   3182  */
   3183 static tnode_t *
   3184 build_bit_shift(op_t op, bool sys, tnode_t *ln, tnode_t *rn)
   3185 {
   3186 	tspec_t	t;
   3187 	tnode_t	*ntn;
   3188 
   3189 	if ((t = rn->tn_type->t_tspec) != INT && t != UINT)
   3190 		rn = convert(CVT, 0, gettyp(INT), rn);
   3191 	ntn = new_tnode(op, sys, ln->tn_type, ln, rn);
   3192 	return ntn;
   3193 }
   3194 
   3195 /*
   3196  * Create a node for COLON.
   3197  */
   3198 static tnode_t *
   3199 build_colon(bool sys, tnode_t *ln, tnode_t *rn)
   3200 {
   3201 	tspec_t	lt, rt, pdt;
   3202 	type_t	*tp;
   3203 	tnode_t	*ntn;
   3204 
   3205 	lt = ln->tn_type->t_tspec;
   3206 	rt = rn->tn_type->t_tspec;
   3207 	pdt = PTRDIFF_TSPEC;
   3208 
   3209 	/*
   3210 	 * Arithmetic types are balanced, all other type combinations
   3211 	 * still need to be handled.
   3212 	 */
   3213 	if (is_arithmetic(lt) && is_arithmetic(rt)) {
   3214 		tp = ln->tn_type;
   3215 	} else if (lt == BOOL && rt == BOOL) {
   3216 		tp = ln->tn_type;
   3217 	} else if (lt == VOID || rt == VOID) {
   3218 		tp = gettyp(VOID);
   3219 	} else if (is_struct_or_union(lt)) {
   3220 		/* Both types must be identical. */
   3221 		lint_assert(is_struct_or_union(rt));
   3222 		lint_assert(ln->tn_type->t_str == rn->tn_type->t_str);
   3223 		if (is_incomplete(ln->tn_type)) {
   3224 			/* unknown operand size, op %s */
   3225 			error(138, op_name(COLON));
   3226 			return NULL;
   3227 		}
   3228 		tp = ln->tn_type;
   3229 	} else if (lt == PTR && is_integer(rt)) {
   3230 		if (rt != pdt) {
   3231 			rn = convert(NOOP, 0, gettyp(pdt), rn);
   3232 			rt = pdt;
   3233 		}
   3234 		tp = ln->tn_type;
   3235 	} else if (rt == PTR && is_integer(lt)) {
   3236 		if (lt != pdt) {
   3237 			ln = convert(NOOP, 0, gettyp(pdt), ln);
   3238 			lt = pdt;
   3239 		}
   3240 		tp = rn->tn_type;
   3241 	} else if (lt == PTR && ln->tn_type->t_subt->t_tspec == VOID) {
   3242 		tp = merge_qualifiers(rn->tn_type, ln->tn_type);
   3243 	} else if (rt == PTR && rn->tn_type->t_subt->t_tspec == VOID) {
   3244 		tp = merge_qualifiers(ln->tn_type, rn->tn_type);
   3245 	} else {
   3246 		/*
   3247 		 * XXX For now we simply take the left type. This is
   3248 		 * probably wrong, if one type contains a function prototype
   3249 		 * and the other one, at the same place, only an old style
   3250 		 * declaration.
   3251 		 */
   3252 		tp = merge_qualifiers(ln->tn_type, rn->tn_type);
   3253 	}
   3254 
   3255 	ntn = new_tnode(COLON, sys, tp, ln, rn);
   3256 
   3257 	return ntn;
   3258 }
   3259 
   3260 /*
   3261  * Create a node for an assignment operator (both = and op= ).
   3262  */
   3263 static tnode_t *
   3264 build_assignment(op_t op, bool sys, tnode_t *ln, tnode_t *rn)
   3265 {
   3266 	tspec_t	lt, rt;
   3267 	tnode_t	*ntn, *ctn;
   3268 
   3269 	lint_assert(ln != NULL);
   3270 	lint_assert(rn != NULL);
   3271 
   3272 	lt = ln->tn_type->t_tspec;
   3273 	rt = rn->tn_type->t_tspec;
   3274 
   3275 	if ((op == ADDASS || op == SUBASS) && lt == PTR) {
   3276 		lint_assert(is_integer(rt));
   3277 		ctn = subt_size_in_bytes(ln->tn_type);
   3278 		if (rn->tn_type->t_tspec != ctn->tn_type->t_tspec)
   3279 			rn = convert(NOOP, 0, ctn->tn_type, rn);
   3280 		rn = new_tnode(MULT, sys, rn->tn_type, rn, ctn);
   3281 		if (rn->tn_left->tn_op == CON)
   3282 			rn = fold(rn);
   3283 	}
   3284 
   3285 	if ((op == ASSIGN || op == RETURN || op == INIT) &&
   3286 	    (lt == STRUCT || rt == STRUCT)) {
   3287 		lint_assert(lt == rt);
   3288 		lint_assert(ln->tn_type->t_str == rn->tn_type->t_str);
   3289 		if (is_incomplete(ln->tn_type)) {
   3290 			if (op == RETURN) {
   3291 				/* cannot return incomplete type */
   3292 				error(212);
   3293 			} else {
   3294 				/* unknown operand size, op %s */
   3295 				error(138, op_name(op));
   3296 			}
   3297 			return NULL;
   3298 		}
   3299 	}
   3300 
   3301 	if (op == SHLASS) {
   3302 		if (portable_size_in_bits(lt) < portable_size_in_bits(rt)) {
   3303 			if (hflag)
   3304 				/* semantics of '%s' change in ANSI C; ... */
   3305 				warning(118, "<<=");
   3306 		}
   3307 	} else if (op != SHRASS) {
   3308 		if (op == ASSIGN || lt != PTR) {
   3309 			if (lt != rt ||
   3310 			    (ln->tn_type->t_bitfield && rn->tn_op == CON)) {
   3311 				rn = convert(op, 0, ln->tn_type, rn);
   3312 				rt = lt;
   3313 			}
   3314 		}
   3315 	}
   3316 
   3317 	ntn = new_tnode(op, sys, ln->tn_type, ln, rn);
   3318 
   3319 	return ntn;
   3320 }
   3321 
   3322 /*
   3323  * Get the size in bytes of type tp->t_subt, as a constant expression of type
   3324  * ptrdiff_t as seen from the target platform.
   3325  */
   3326 static tnode_t *
   3327 subt_size_in_bytes(type_t *tp)
   3328 {
   3329 	int elem, elsz_in_bits;
   3330 
   3331 	lint_assert(tp->t_tspec == PTR);
   3332 	tp = tp->t_subt;
   3333 
   3334 	elem = 1;
   3335 	elsz_in_bits = 0;
   3336 
   3337 	while (tp->t_tspec == ARRAY) {
   3338 		elem *= tp->t_dim;
   3339 		tp = tp->t_subt;
   3340 	}
   3341 
   3342 	switch (tp->t_tspec) {
   3343 	case FUNC:
   3344 		/* pointer to function is not allowed here */
   3345 		error(110);
   3346 		break;
   3347 	case VOID:
   3348 		/* cannot do pointer arithmetic on operand of unknown size */
   3349 		gnuism(136);
   3350 		break;
   3351 	case STRUCT:
   3352 	case UNION:
   3353 		if ((elsz_in_bits = tp->t_str->sou_size_in_bits) == 0)
   3354 			/* cannot do pointer arithmetic on operand of ... */
   3355 			error(136);
   3356 		break;
   3357 	case ENUM:
   3358 		if (is_incomplete(tp)) {
   3359 			/* cannot do pointer arithmetic on operand of ... */
   3360 			warning(136);
   3361 		}
   3362 		/* FALLTHROUGH */
   3363 	default:
   3364 		if ((elsz_in_bits = size_in_bits(tp->t_tspec)) == 0) {
   3365 			/* cannot do pointer arithmetic on operand of ... */
   3366 			error(136);
   3367 		} else {
   3368 			lint_assert(elsz_in_bits != -1);
   3369 		}
   3370 		break;
   3371 	}
   3372 
   3373 	if (elem == 0 && elsz_in_bits != 0) {
   3374 		/* cannot do pointer arithmetic on operand of unknown size */
   3375 		error(136);
   3376 	}
   3377 
   3378 	if (elsz_in_bits == 0)
   3379 		elsz_in_bits = CHAR_SIZE;
   3380 
   3381 	return build_integer_constant(PTRDIFF_TSPEC,
   3382 	    (int64_t)(elem * elsz_in_bits / CHAR_SIZE));
   3383 }
   3384 
   3385 /*
   3386  * XXX
   3387  * Note: There appear to be a number of bugs in detecting overflow in
   3388  * this function. An audit and a set of proper regression tests are needed.
   3389  *     --Perry Metzger, Nov. 16, 2001
   3390  */
   3391 /*
   3392  * Do only as much as necessary to compute constant expressions.
   3393  * Called only if the operator allows folding and all operands are constants.
   3394  */
   3395 static tnode_t *
   3396 fold(tnode_t *tn)
   3397 {
   3398 	val_t *v;
   3399 	tspec_t t;
   3400 	bool utyp, ovfl;
   3401 	int64_t sl, sr = 0, q = 0, mask;
   3402 	uint64_t ul, ur = 0;
   3403 	tnode_t *cn;
   3404 
   3405 	v = xcalloc(1, sizeof(*v));
   3406 	v->v_tspec = tn->tn_type->t_tspec;
   3407 
   3408 	t = tn->tn_left->tn_type->t_tspec;
   3409 	utyp = !is_integer(t) || is_uinteger(t);
   3410 	ul = sl = tn->tn_left->tn_val->v_quad;
   3411 	if (is_binary(tn))
   3412 		ur = sr = tn->tn_right->tn_val->v_quad;
   3413 
   3414 	mask = value_bits(size_in_bits(t));
   3415 	ovfl = false;
   3416 
   3417 	switch (tn->tn_op) {
   3418 	case UPLUS:
   3419 		q = sl;
   3420 		break;
   3421 	case UMINUS:
   3422 		q = sl == INT64_MIN ? sl : -sl;
   3423 		if (sl != 0 && msb(q, t) == msb(sl, t))
   3424 			ovfl = true;
   3425 		break;
   3426 	case COMPL:
   3427 		q = ~sl;
   3428 		break;
   3429 	case MULT:
   3430 		if (utyp) {
   3431 			q = ul * ur;
   3432 			if (q != (q & mask))
   3433 				ovfl = true;
   3434 			else if ((ul != 0) && ((q / ul) != ur))
   3435 				ovfl = true;
   3436 		} else {
   3437 			q = sl * sr;
   3438 			if (msb(q, t) != (msb(sl, t) ^ msb(sr, t)))
   3439 				ovfl = true;
   3440 		}
   3441 		break;
   3442 	case DIV:
   3443 		if (sr == 0) {
   3444 			/* division by 0 */
   3445 			error(139);
   3446 			q = utyp ? -1 : INT64_MAX;
   3447 		} else {
   3448 			q = utyp ? (int64_t)(ul / ur) : sl / sr;
   3449 		}
   3450 		break;
   3451 	case MOD:
   3452 		if (sr == 0) {
   3453 			/* modulus by 0 */
   3454 			error(140);
   3455 			q = 0;
   3456 		} else {
   3457 			q = utyp ? (int64_t)(ul % ur) : sl % sr;
   3458 		}
   3459 		break;
   3460 	case PLUS:
   3461 		q = utyp ? (int64_t)(ul + ur) : sl + sr;
   3462 		if (msb(sl, t) && msb(sr, t) && !msb(q, t))
   3463 			ovfl = true;
   3464 		if (!utyp && !msb(sl, t) && !msb(sr, t) && msb(q, t))
   3465 			ovfl = true;
   3466 		break;
   3467 	case MINUS:
   3468 		q = utyp ? (int64_t)(ul - ur) : sl - sr;
   3469 		if (!utyp && msb(sl, t) && !msb(sr, t) && !msb(q, t))
   3470 			ovfl = true;
   3471 		if (!msb(sl, t) && msb(sr, t) && msb(q, t))
   3472 			ovfl = true;
   3473 		break;
   3474 	case SHL:
   3475 		q = utyp ? (int64_t)(ul << sr) : sl << sr;
   3476 		break;
   3477 	case SHR:
   3478 		/*
   3479 		 * The sign must be explicitly extended because
   3480 		 * shifts of signed values are implementation dependent.
   3481 		 */
   3482 		q = ul >> sr;
   3483 		q = convert_integer(q, t, size_in_bits(t) - (int)sr);
   3484 		break;
   3485 	case LT:
   3486 		q = (utyp ? ul < ur : sl < sr) ? 1 : 0;
   3487 		break;
   3488 	case LE:
   3489 		q = (utyp ? ul <= ur : sl <= sr) ? 1 : 0;
   3490 		break;
   3491 	case GE:
   3492 		q = (utyp ? ul >= ur : sl >= sr) ? 1 : 0;
   3493 		break;
   3494 	case GT:
   3495 		q = (utyp ? ul > ur : sl > sr) ? 1 : 0;
   3496 		break;
   3497 	case EQ:
   3498 		q = (utyp ? ul == ur : sl == sr) ? 1 : 0;
   3499 		break;
   3500 	case NE:
   3501 		q = (utyp ? ul != ur : sl != sr) ? 1 : 0;
   3502 		break;
   3503 	case BITAND:
   3504 		q = utyp ? (int64_t)(ul & ur) : sl & sr;
   3505 		break;
   3506 	case BITXOR:
   3507 		q = utyp ? (int64_t)(ul ^ ur) : sl ^ sr;
   3508 		break;
   3509 	case BITOR:
   3510 		q = utyp ? (int64_t)(ul | ur) : sl | sr;
   3511 		break;
   3512 	default:
   3513 		lint_assert(/*CONSTCOND*/false);
   3514 	}
   3515 
   3516 	/* XXX does not work for quads. */
   3517 	if (ovfl ||
   3518 	    ((uint64_t)(q | mask) != ~(uint64_t)0 && (q & ~mask) != 0)) {
   3519 		if (hflag)
   3520 			/* integer overflow detected, op '%s' */
   3521 			warning(141, op_name(tn->tn_op));
   3522 	}
   3523 
   3524 	v->v_quad = convert_integer(q, t, 0);
   3525 
   3526 	cn = build_constant(tn->tn_type, v);
   3527 	if (tn->tn_left->tn_system_dependent)
   3528 		cn->tn_system_dependent = true;
   3529 	if (is_binary(tn) && tn->tn_right->tn_system_dependent)
   3530 		cn->tn_system_dependent = true;
   3531 
   3532 	return cn;
   3533 }
   3534 
   3535 /*
   3536  * Fold constant nodes, as much as is needed for comparing the value with 0.
   3537  */
   3538 static tnode_t *
   3539 fold_bool(tnode_t *tn)
   3540 {
   3541 	bool	l, r;
   3542 	val_t	*v;
   3543 
   3544 	v = xcalloc(1, sizeof(*v));
   3545 	v->v_tspec = tn->tn_type->t_tspec;
   3546 	lint_assert(v->v_tspec == INT || (Tflag && v->v_tspec == BOOL));
   3547 
   3548 	l = constant_is_nonzero(tn->tn_left);
   3549 	r = is_binary(tn) && constant_is_nonzero(tn->tn_right);
   3550 
   3551 	switch (tn->tn_op) {
   3552 	case NOT:
   3553 		if (hflag && !constcond_flag)
   3554 			/* constant argument to '!' */
   3555 			warning(239);
   3556 		v->v_quad = !l ? 1 : 0;
   3557 		break;
   3558 	case LOGAND:
   3559 		v->v_quad = l && r ? 1 : 0;
   3560 		break;
   3561 	case LOGOR:
   3562 		v->v_quad = l || r ? 1 : 0;
   3563 		break;
   3564 	default:
   3565 		lint_assert(/*CONSTCOND*/false);
   3566 	}
   3567 
   3568 	return build_constant(tn->tn_type, v);
   3569 }
   3570 
   3571 static ldbl_t
   3572 floating_error_value(tspec_t t, ldbl_t lv)
   3573 {
   3574 	if (t == FLOAT) {
   3575 		return lv < 0 ? -FLT_MAX : FLT_MAX;
   3576 	} else if (t == DOUBLE) {
   3577 		return lv < 0 ? -DBL_MAX : DBL_MAX;
   3578 	} else {
   3579 		/* LINTED 248: floating-point constant out of range */
   3580 		ldbl_t max = LDBL_MAX;
   3581 		return lv < 0 ? -max : max;
   3582 	}
   3583 }
   3584 
   3585 /*
   3586  * Fold constant nodes having operands with floating point type.
   3587  */
   3588 static tnode_t *
   3589 fold_float(tnode_t *tn)
   3590 {
   3591 	val_t	*v;
   3592 	tspec_t	t;
   3593 	ldbl_t	lv, rv = 0;
   3594 
   3595 	fpe = 0;
   3596 	v = xcalloc(1, sizeof(*v));
   3597 	v->v_tspec = t = tn->tn_type->t_tspec;
   3598 
   3599 	lint_assert(is_floating(t));
   3600 	lint_assert(t == tn->tn_left->tn_type->t_tspec);
   3601 	lint_assert(!is_binary(tn) || t == tn->tn_right->tn_type->t_tspec);
   3602 
   3603 	lv = tn->tn_left->tn_val->v_ldbl;
   3604 	if (is_binary(tn))
   3605 		rv = tn->tn_right->tn_val->v_ldbl;
   3606 
   3607 	switch (tn->tn_op) {
   3608 	case UPLUS:
   3609 		v->v_ldbl = lv;
   3610 		break;
   3611 	case UMINUS:
   3612 		v->v_ldbl = -lv;
   3613 		break;
   3614 	case MULT:
   3615 		v->v_ldbl = lv * rv;
   3616 		break;
   3617 	case DIV:
   3618 		if (rv == 0.0) {
   3619 			/* division by 0 */
   3620 			error(139);
   3621 			v->v_ldbl = floating_error_value(t, lv);
   3622 		} else {
   3623 			v->v_ldbl = lv / rv;
   3624 		}
   3625 		break;
   3626 	case PLUS:
   3627 		v->v_ldbl = lv + rv;
   3628 		break;
   3629 	case MINUS:
   3630 		v->v_ldbl = lv - rv;
   3631 		break;
   3632 	case LT:
   3633 		v->v_quad = lv < rv ? 1 : 0;
   3634 		break;
   3635 	case LE:
   3636 		v->v_quad = lv <= rv ? 1 : 0;
   3637 		break;
   3638 	case GE:
   3639 		v->v_quad = lv >= rv ? 1 : 0;
   3640 		break;
   3641 	case GT:
   3642 		v->v_quad = lv > rv ? 1 : 0;
   3643 		break;
   3644 	case EQ:
   3645 		v->v_quad = lv == rv ? 1 : 0;
   3646 		break;
   3647 	case NE:
   3648 		v->v_quad = lv != rv ? 1 : 0;
   3649 		break;
   3650 	default:
   3651 		lint_assert(/*CONSTCOND*/false);
   3652 	}
   3653 
   3654 	lint_assert(fpe != 0 || isnan((double)v->v_ldbl) == 0);
   3655 	if (fpe != 0 || isfinite((double)v->v_ldbl) == 0 ||
   3656 	    (t == FLOAT &&
   3657 	     (v->v_ldbl > FLT_MAX || v->v_ldbl < -FLT_MAX)) ||
   3658 	    (t == DOUBLE &&
   3659 	     (v->v_ldbl > DBL_MAX || v->v_ldbl < -DBL_MAX))) {
   3660 		/* floating point overflow detected, op %s */
   3661 		warning(142, op_name(tn->tn_op));
   3662 		v->v_ldbl = floating_error_value(t, v->v_ldbl);
   3663 		fpe = 0;
   3664 	}
   3665 
   3666 	return build_constant(tn->tn_type, v);
   3667 }
   3668 
   3669 
   3670 /*
   3671  * Create a constant node for sizeof.
   3672  */
   3673 tnode_t *
   3674 build_sizeof(const type_t *tp)
   3675 {
   3676 	unsigned int size_in_bytes = type_size_in_bits(tp) / CHAR_SIZE;
   3677 	tnode_t *tn = build_integer_constant(SIZEOF_TSPEC, size_in_bytes);
   3678 	tn->tn_system_dependent = true;
   3679 	debug_step("build_sizeof '%s' = %u", type_name(tp), size_in_bytes);
   3680 	return tn;
   3681 }
   3682 
   3683 /*
   3684  * Create a constant node for offsetof.
   3685  */
   3686 /* ARGSUSED */ /* See implementation comments. */
   3687 tnode_t *
   3688 build_offsetof(const type_t *tp, const sym_t *sym)
   3689 {
   3690 	unsigned int offset_in_bytes;
   3691 	tnode_t *tn;
   3692 
   3693 	if (!is_struct_or_union(tp->t_tspec))
   3694 		/* unacceptable operand of '%s' */
   3695 		error(111, "offsetof");
   3696 
   3697 	/* XXX: wrong size, no checking for sym fixme */
   3698 	offset_in_bytes = type_size_in_bits(tp) / CHAR_SIZE;
   3699 	tn = build_integer_constant(SIZEOF_TSPEC, offset_in_bytes);
   3700 	tn->tn_system_dependent = true;
   3701 	return tn;
   3702 }
   3703 
   3704 unsigned int
   3705 type_size_in_bits(const type_t *tp)
   3706 {
   3707 	unsigned int elem, elsz;
   3708 	bool	flex;
   3709 
   3710 	elem = 1;
   3711 	flex = false;
   3712 	lint_assert(tp != NULL);
   3713 	while (tp->t_tspec == ARRAY) {
   3714 		flex = true;	/* allow c99 flex arrays [] [0] */
   3715 		elem *= tp->t_dim;
   3716 		tp = tp->t_subt;
   3717 	}
   3718 	if (elem == 0) {
   3719 		if (!flex) {
   3720 			/* cannot take size/alignment of incomplete type */
   3721 			error(143);
   3722 			elem = 1;
   3723 		}
   3724 	}
   3725 	switch (tp->t_tspec) {
   3726 	case FUNC:
   3727 		/* cannot take size/alignment of function type '%s' */
   3728 		error(144, type_name(tp));
   3729 		elsz = 1;
   3730 		break;
   3731 	case STRUCT:
   3732 	case UNION:
   3733 		if (is_incomplete(tp)) {
   3734 			/* cannot take size/alignment of incomplete type */
   3735 			error(143);
   3736 			elsz = 1;
   3737 		} else {
   3738 			elsz = tp->t_str->sou_size_in_bits;
   3739 		}
   3740 		break;
   3741 	case ENUM:
   3742 		if (is_incomplete(tp)) {
   3743 			/* cannot take size/alignment of incomplete type */
   3744 			warning(143);
   3745 		}
   3746 		/* FALLTHROUGH */
   3747 	default:
   3748 		if (tp->t_bitfield) {
   3749 			/* cannot take size/alignment of bit-field */
   3750 			error(145);
   3751 		}
   3752 		if (tp->t_tspec == VOID) {
   3753 			/* cannot take size/alignment of void */
   3754 			error(146);
   3755 			elsz = 1;
   3756 		} else {
   3757 			elsz = size_in_bits(tp->t_tspec);
   3758 			lint_assert(elsz > 0);
   3759 		}
   3760 		break;
   3761 	}
   3762 
   3763 	return elem * elsz;
   3764 }
   3765 
   3766 tnode_t *
   3767 build_alignof(const type_t *tp)
   3768 {
   3769 	switch (tp->t_tspec) {
   3770 	case ARRAY:
   3771 		break;
   3772 
   3773 	case FUNC:
   3774 		/* cannot take size/alignment of function type '%s' */
   3775 		error(144, type_name(tp));
   3776 		return 0;
   3777 
   3778 	case STRUCT:
   3779 	case UNION:
   3780 		if (is_incomplete(tp)) {
   3781 			/* cannot take size/alignment of incomplete type */
   3782 			error(143);
   3783 			return 0;
   3784 		}
   3785 		break;
   3786 	case ENUM:
   3787 		break;
   3788 	default:
   3789 		if (tp->t_bitfield) {
   3790 			/* cannot take size/alignment of bit-field */
   3791 			error(145);
   3792 			return 0;
   3793 		}
   3794 		if (tp->t_tspec == VOID) {
   3795 			/* cannot take size/alignment of void */
   3796 			error(146);
   3797 			return 0;
   3798 		}
   3799 		break;
   3800 	}
   3801 
   3802 	return build_integer_constant(SIZEOF_TSPEC,
   3803 	    (int64_t)alignment_in_bits(tp) / CHAR_SIZE);
   3804 }
   3805 
   3806 /*
   3807  * Type casts.
   3808  */
   3809 tnode_t *
   3810 cast(tnode_t *tn, type_t *tp)
   3811 {
   3812 	tspec_t	nt, ot;
   3813 
   3814 	if (tn == NULL)
   3815 		return NULL;
   3816 
   3817 	tn = cconv(tn);
   3818 
   3819 	lint_assert(tp != NULL);
   3820 	nt = tp->t_tspec;
   3821 	ot = tn->tn_type->t_tspec;
   3822 
   3823 	if (nt == VOID) {
   3824 		/*
   3825 		 * C90 6.3.4, C99 6.5.4p2 and C11 6.5.4p2 allow any type to
   3826 		 * be cast to void.  The only other allowed casts are from a
   3827 		 * scalar type to a scalar type.
   3828 		 */
   3829 	} else if (nt == UNION) {
   3830 		sym_t *m;
   3831 		struct_or_union *str = tp->t_str;
   3832 		if (!allow_gcc) {
   3833 			/* union cast is a GCC extension */
   3834 			error(328);
   3835 			return NULL;
   3836 		}
   3837 		for (m = str->sou_first_member; m != NULL; m = m->s_next) {
   3838 			if (eqtype(m->s_type, tn->tn_type,
   3839 			    false, false, NULL)) {
   3840 				tn = expr_alloc_tnode();
   3841 				tn->tn_op = CVT;
   3842 				tn->tn_type = tp;
   3843 				tn->tn_cast = true;
   3844 				tn->tn_right = NULL;
   3845 				return tn;
   3846 			}
   3847 		}
   3848 		/* type '%s' is not a member of '%s' */
   3849 		error(329, type_name(tn->tn_type), type_name(tp));
   3850 		return NULL;
   3851 	} else if (nt == STRUCT || nt == ARRAY || nt == FUNC) {
   3852 		/* Casting to a struct is an undocumented GCC extension. */
   3853 		if (!(allow_gcc && nt == STRUCT))
   3854 			goto invalid_cast;
   3855 	} else if (is_struct_or_union(ot)) {
   3856 		goto invalid_cast;
   3857 	} else if (ot == VOID) {
   3858 		/* improper cast of void expression */
   3859 		error(148);
   3860 		return NULL;
   3861 	} else if (is_integer(nt) && is_scalar(ot)) {
   3862 		/* ok */
   3863 	} else if (is_floating(nt) && is_arithmetic(ot)) {
   3864 		/* ok */
   3865 	} else if (nt == PTR && is_integer(ot)) {
   3866 		/* ok */
   3867 	} else if (nt == PTR && ot == PTR) {
   3868 		if (!tp->t_subt->t_const && tn->tn_type->t_subt->t_const) {
   3869 			if (hflag)
   3870 				/* cast discards 'const' from type '%s' */
   3871 				warning(275, type_name(tn->tn_type));
   3872 		}
   3873 	} else
   3874 		goto invalid_cast;
   3875 
   3876 	tn = convert(CVT, 0, tp, tn);
   3877 	tn->tn_cast = true;
   3878 
   3879 	return tn;
   3880 
   3881 invalid_cast:
   3882 	/* invalid cast from '%s' to '%s' */
   3883 	error(147, type_name(tn->tn_type), type_name(tp));
   3884 	return NULL;
   3885 }
   3886 
   3887 /*
   3888  * Create the node for a function argument.
   3889  * All necessary conversions and type checks are done in
   3890  * build_function_call because build_function_argument has no
   3891  * information about expected argument types.
   3892  */
   3893 tnode_t *
   3894 build_function_argument(tnode_t *args, tnode_t *arg)
   3895 {
   3896 	tnode_t	*ntn;
   3897 
   3898 	/*
   3899 	 * If there was a serious error in the expression for the argument,
   3900 	 * create a dummy argument so the positions of the remaining arguments
   3901 	 * will not change.
   3902 	 */
   3903 	if (arg == NULL)
   3904 		arg = build_integer_constant(INT, 0);
   3905 
   3906 	ntn = new_tnode(PUSH, arg->tn_sys, arg->tn_type, arg, args);
   3907 
   3908 	return ntn;
   3909 }
   3910 
   3911 /*
   3912  * Create the node for a function call. Also check types of
   3913  * function arguments and insert conversions, if necessary.
   3914  */
   3915 tnode_t *
   3916 build_function_call(tnode_t *func, bool sys, tnode_t *args)
   3917 {
   3918 	tnode_t	*ntn;
   3919 	op_t	fcop;
   3920 
   3921 	if (func == NULL)
   3922 		return NULL;
   3923 
   3924 	if (func->tn_op == NAME && func->tn_type->t_tspec == FUNC) {
   3925 		fcop = CALL;
   3926 	} else {
   3927 		fcop = ICALL;
   3928 	}
   3929 
   3930 	check_ctype_function_call(func, args);
   3931 
   3932 	/*
   3933 	 * after cconv() func will always be a pointer to a function
   3934 	 * if it is a valid function designator.
   3935 	 */
   3936 	func = cconv(func);
   3937 
   3938 	if (func->tn_type->t_tspec != PTR ||
   3939 	    func->tn_type->t_subt->t_tspec != FUNC) {
   3940 		/* illegal function (type %s) */
   3941 		error(149, type_name(func->tn_type));
   3942 		return NULL;
   3943 	}
   3944 
   3945 	args = check_function_arguments(func->tn_type->t_subt, args);
   3946 
   3947 	ntn = new_tnode(fcop, sys, func->tn_type->t_subt->t_subt, func, args);
   3948 
   3949 	return ntn;
   3950 }
   3951 
   3952 /*
   3953  * Check types of all function arguments and insert conversions,
   3954  * if necessary.
   3955  */
   3956 static tnode_t *
   3957 check_function_arguments(type_t *ftp, tnode_t *args)
   3958 {
   3959 	tnode_t	*arg;
   3960 	sym_t	*asym;
   3961 	tspec_t	at;
   3962 	int	narg, npar, n, i;
   3963 
   3964 	/* get # of args in the prototype */
   3965 	npar = 0;
   3966 	for (asym = ftp->t_args; asym != NULL; asym = asym->s_next)
   3967 		npar++;
   3968 
   3969 	/* get # of args in function call */
   3970 	narg = 0;
   3971 	for (arg = args; arg != NULL; arg = arg->tn_right)
   3972 		narg++;
   3973 
   3974 	asym = ftp->t_args;
   3975 	if (ftp->t_proto && npar != narg && !(ftp->t_vararg && npar < narg)) {
   3976 		/* argument mismatch: %d arg%s passed, %d expected */
   3977 		error(150, narg, narg > 1 ? "s" : "", npar);
   3978 		asym = NULL;
   3979 	}
   3980 
   3981 	for (n = 1; n <= narg; n++) {
   3982 
   3983 		/*
   3984 		 * The rightmost argument is at the top of the argument
   3985 		 * subtree.
   3986 		 */
   3987 		for (i = narg, arg = args; i > n; i--, arg = arg->tn_right)
   3988 			continue;
   3989 
   3990 		/* some things which are always not allowed */
   3991 		if ((at = arg->tn_left->tn_type->t_tspec) == VOID) {
   3992 			/* void expressions may not be arguments, arg #%d */
   3993 			error(151, n);
   3994 			return NULL;
   3995 		} else if (is_struct_or_union(at) &&
   3996 			   is_incomplete(arg->tn_left->tn_type)) {
   3997 			/* argument cannot have unknown size, arg #%d */
   3998 			error(152, n);
   3999 			return NULL;
   4000 		} else if (is_integer(at) &&
   4001 			   arg->tn_left->tn_type->t_is_enum &&
   4002 			   is_incomplete(arg->tn_left->tn_type)) {
   4003 			/* argument cannot have unknown size, arg #%d */
   4004 			warning(152, n);
   4005 		}
   4006 
   4007 		/* class conversions (arg in value context) */
   4008 		arg->tn_left = cconv(arg->tn_left);
   4009 
   4010 		if (asym != NULL) {
   4011 			arg->tn_left = check_prototype_argument(
   4012 			    n, asym->s_type, arg->tn_left);
   4013 		} else {
   4014 			arg->tn_left = promote(NOOP, true, arg->tn_left);
   4015 		}
   4016 		arg->tn_type = arg->tn_left->tn_type;
   4017 
   4018 		if (asym != NULL)
   4019 			asym = asym->s_next;
   4020 	}
   4021 
   4022 	return args;
   4023 }
   4024 
   4025 /*
   4026  * Compare the type of an argument with the corresponding type of a
   4027  * prototype parameter. If it is a valid combination, but both types
   4028  * are not the same, insert a conversion to convert the argument into
   4029  * the type of the parameter.
   4030  */
   4031 static tnode_t *
   4032 check_prototype_argument(
   4033 	int	n,		/* pos of arg */
   4034 	type_t	*tp,		/* expected type (from prototype) */
   4035 	tnode_t	*tn)		/* argument */
   4036 {
   4037 	tnode_t	*ln;
   4038 	bool	dowarn;
   4039 
   4040 	ln = xcalloc(1, sizeof(*ln));
   4041 	ln->tn_type = expr_unqualified_type(tp);
   4042 	ln->tn_lvalue = true;
   4043 	if (typeok(FARG, n, ln, tn)) {
   4044 		if (!eqtype(tp, tn->tn_type,
   4045 		    true, false, (dowarn = false, &dowarn)) || dowarn)
   4046 			tn = convert(FARG, n, tp, tn);
   4047 	}
   4048 	free(ln);
   4049 	return tn;
   4050 }
   4051 
   4052 /*
   4053  * Return the value of an integral constant expression.
   4054  * If the expression is not constant or its type is not an integer
   4055  * type, an error message is printed.
   4056  */
   4057 val_t *
   4058 constant(tnode_t *tn, bool required)
   4059 {
   4060 	val_t	*v;
   4061 
   4062 	if (tn != NULL)
   4063 		tn = cconv(tn);
   4064 	if (tn != NULL)
   4065 		tn = promote(NOOP, false, tn);
   4066 
   4067 	v = xcalloc(1, sizeof(*v));
   4068 
   4069 	if (tn == NULL) {
   4070 		lint_assert(nerr != 0);
   4071 		debug_step("constant node is null; returning 1 instead");
   4072 		v->v_tspec = INT;
   4073 		v->v_quad = 1;
   4074 		return v;
   4075 	}
   4076 
   4077 	v->v_tspec = tn->tn_type->t_tspec;
   4078 
   4079 	if (tn->tn_op == CON) {
   4080 		lint_assert(tn->tn_type->t_tspec == tn->tn_val->v_tspec);
   4081 		if (is_integer(tn->tn_val->v_tspec)) {
   4082 			v->v_unsigned_since_c90 =
   4083 			    tn->tn_val->v_unsigned_since_c90;
   4084 			v->v_quad = tn->tn_val->v_quad;
   4085 			return v;
   4086 		}
   4087 		v->v_quad = tn->tn_val->v_ldbl;
   4088 	} else {
   4089 		v->v_quad = 1;
   4090 	}
   4091 
   4092 	if (required)
   4093 		/* integral constant expression expected */
   4094 		error(55);
   4095 	else
   4096 		/* variable array dimension is a C99/GCC extension */
   4097 		c99ism(318);
   4098 
   4099 	if (!is_integer(v->v_tspec))
   4100 		v->v_tspec = INT;
   4101 
   4102 	return v;
   4103 }
   4104 
   4105 static bool
   4106 is_constcond_false(const tnode_t *tn, tspec_t t)
   4107 {
   4108 	return (t == BOOL || t == INT) &&
   4109 	       tn->tn_op == CON && tn->tn_val->v_quad == 0;
   4110 }
   4111 
   4112 /*
   4113  * Perform some tests on expressions which can't be done in build_binary()
   4114  * and functions called by build_binary(). These tests must be done here
   4115  * because we need some information about the context in which the operations
   4116  * are performed.
   4117  * After all tests are performed and dofreeblk is true, expr() frees the
   4118  * memory which is used for the expression.
   4119  */
   4120 void
   4121 expr(tnode_t *tn, bool vctx, bool cond, bool dofreeblk, bool is_do_while)
   4122 {
   4123 
   4124 	if (tn == NULL) {	/* in case of errors */
   4125 		expr_free_all();
   4126 		return;
   4127 	}
   4128 
   4129 	/* expr() is also called in global initializations */
   4130 	if (dcs->d_kind != DK_EXTERN && !is_do_while)
   4131 		check_statement_reachable();
   4132 
   4133 	check_expr_misc(tn, vctx, cond, !cond, false, false, false);
   4134 	if (tn->tn_op == ASSIGN) {
   4135 		if (hflag && cond)
   4136 			/* assignment in conditional context */
   4137 			warning(159);
   4138 	} else if (tn->tn_op == CON) {
   4139 		if (hflag && cond && !constcond_flag &&
   4140 		    !tn->tn_system_dependent &&
   4141 		    !(is_do_while &&
   4142 		      is_constcond_false(tn, tn->tn_type->t_tspec)))
   4143 			/* constant in conditional context */
   4144 			warning(161);
   4145 	}
   4146 	if (!modtab[tn->tn_op].m_has_side_effect) {
   4147 		/*
   4148 		 * for left operands of COMMA this warning is already
   4149 		 * printed
   4150 		 */
   4151 		if (tn->tn_op != COMMA && !vctx && !cond)
   4152 			check_null_effect(tn);
   4153 	}
   4154 	debug_node(tn);
   4155 
   4156 	/* free the tree memory */
   4157 	if (dofreeblk)
   4158 		expr_free_all();
   4159 }
   4160 
   4161 static bool
   4162 has_side_effect(const tnode_t *tn) /* NOLINT(misc-no-recursion) */
   4163 {
   4164 	op_t op = tn->tn_op;
   4165 
   4166 	if (modtab[op].m_has_side_effect)
   4167 		return true;
   4168 
   4169 	if (op == CVT && tn->tn_type->t_tspec == VOID)
   4170 		return has_side_effect(tn->tn_left);
   4171 
   4172 	/* XXX: Why not has_side_effect(tn->tn_left) as well? */
   4173 	if (op == LOGAND || op == LOGOR)
   4174 		return has_side_effect(tn->tn_right);
   4175 
   4176 	/* XXX: Why not has_side_effect(tn->tn_left) as well? */
   4177 	if (op == QUEST)
   4178 		return has_side_effect(tn->tn_right);
   4179 
   4180 	if (op == COLON || op == COMMA) {
   4181 		return has_side_effect(tn->tn_left) ||
   4182 		       has_side_effect(tn->tn_right);
   4183 	}
   4184 
   4185 	return false;
   4186 }
   4187 
   4188 static bool
   4189 is_void_cast(const tnode_t *tn)
   4190 {
   4191 
   4192 	return tn->tn_op == CVT && tn->tn_cast &&
   4193 	       tn->tn_type->t_tspec == VOID;
   4194 }
   4195 
   4196 static bool
   4197 is_local_symbol(const tnode_t *tn)
   4198 {
   4199 
   4200 	return tn->tn_op == LOAD &&
   4201 	       tn->tn_left->tn_op == NAME &&
   4202 	       tn->tn_left->tn_sym->s_scl == AUTO;
   4203 }
   4204 
   4205 static bool
   4206 is_int_constant_zero(const tnode_t *tn)
   4207 {
   4208 
   4209 	return tn->tn_op == CON &&
   4210 	       tn->tn_type->t_tspec == INT &&
   4211 	       tn->tn_val->v_quad == 0;
   4212 }
   4213 
   4214 static void
   4215 check_null_effect(const tnode_t *tn)
   4216 {
   4217 
   4218 	if (!hflag)
   4219 		return;
   4220 	if (has_side_effect(tn))
   4221 		return;
   4222 	if (is_void_cast(tn) && is_local_symbol(tn->tn_left))
   4223 		return;
   4224 	if (is_void_cast(tn) && is_int_constant_zero(tn->tn_left))
   4225 		return;
   4226 
   4227 	/* expression has null effect */
   4228 	warning(129);
   4229 }
   4230 
   4231 static void
   4232 check_expr_addr(const tnode_t *ln, bool szof, bool fcall)
   4233 {
   4234 	/* XXX: Taking warn_about_unreachable into account here feels wrong. */
   4235 	if (ln->tn_op == NAME && (reached || !warn_about_unreachable)) {
   4236 		if (!szof)
   4237 			mark_as_set(ln->tn_sym);
   4238 		mark_as_used(ln->tn_sym, fcall, szof);
   4239 	}
   4240 	if (ln->tn_op == INDIR && ln->tn_left->tn_op == PLUS)
   4241 		/* check the range of array indices */
   4242 		check_array_index(ln->tn_left, true);
   4243 }
   4244 
   4245 static void
   4246 check_expr_load(const tnode_t *ln)
   4247 {
   4248 	if (ln->tn_op == INDIR && ln->tn_left->tn_op == PLUS)
   4249 		/* check the range of array indices */
   4250 		check_array_index(ln->tn_left, false);
   4251 }
   4252 
   4253 static void
   4254 check_expr_side_effect(const tnode_t *ln, bool szof)
   4255 {
   4256 	scl_t sc;
   4257 	dinfo_t *di;
   4258 
   4259 	/* XXX: Taking warn_about_unreachable into account here feels wrong. */
   4260 	if (ln->tn_op == NAME && (reached || !warn_about_unreachable)) {
   4261 		sc = ln->tn_sym->s_scl;
   4262 		/*
   4263 		 * Look if there was a asm statement in one of the
   4264 		 * compound statements we are in. If not, we don't
   4265 		 * print a warning.
   4266 		 */
   4267 		for (di = dcs; di != NULL; di = di->d_enclosing) {
   4268 			if (di->d_asm)
   4269 				break;
   4270 		}
   4271 		if (sc != EXTERN && sc != STATIC &&
   4272 		    !ln->tn_sym->s_set && !szof && di == NULL) {
   4273 			/* %s may be used before set */
   4274 			warning(158, ln->tn_sym->s_name);
   4275 			mark_as_set(ln->tn_sym);
   4276 		}
   4277 		mark_as_used(ln->tn_sym, false, false);
   4278 	}
   4279 }
   4280 
   4281 static void
   4282 check_expr_assign(const tnode_t *ln, bool szof)
   4283 {
   4284 	/* XXX: Taking warn_about_unreachable into account here feels wrong. */
   4285 	if (ln->tn_op == NAME && !szof && (reached || !warn_about_unreachable)) {
   4286 		mark_as_set(ln->tn_sym);
   4287 		if (ln->tn_sym->s_scl == EXTERN)
   4288 			outusg(ln->tn_sym);
   4289 	}
   4290 	if (ln->tn_op == INDIR && ln->tn_left->tn_op == PLUS)
   4291 		/* check the range of array indices */
   4292 		check_array_index(ln->tn_left, false);
   4293 }
   4294 
   4295 static void
   4296 check_expr_call(const tnode_t *tn, const tnode_t *ln,
   4297 		bool szof, bool vctx, bool cond, bool retval_discarded)
   4298 {
   4299 	lint_assert(ln->tn_op == ADDR);
   4300 	lint_assert(ln->tn_left->tn_op == NAME);
   4301 	if (!szof &&
   4302 	    !is_compiler_builtin(ln->tn_left->tn_sym->s_name))
   4303 		outcall(tn, vctx || cond, retval_discarded);
   4304 }
   4305 
   4306 static bool
   4307 check_expr_op(const tnode_t *tn, op_t op, const tnode_t *ln,
   4308 	      bool szof, bool fcall, bool vctx, bool cond,
   4309 	      bool retval_discarded, bool eqwarn)
   4310 {
   4311 	switch (op) {
   4312 	case ADDR:
   4313 		check_expr_addr(ln, szof, fcall);
   4314 		break;
   4315 	case LOAD:
   4316 		check_expr_load(ln);
   4317 		/* FALLTHROUGH */
   4318 	case PUSH:
   4319 	case INCBEF:
   4320 	case DECBEF:
   4321 	case INCAFT:
   4322 	case DECAFT:
   4323 	case ADDASS:
   4324 	case SUBASS:
   4325 	case MULASS:
   4326 	case DIVASS:
   4327 	case MODASS:
   4328 	case ANDASS:
   4329 	case ORASS:
   4330 	case XORASS:
   4331 	case SHLASS:
   4332 	case SHRASS:
   4333 	case REAL:
   4334 	case IMAG:
   4335 		check_expr_side_effect(ln, szof);
   4336 		break;
   4337 	case ASSIGN:
   4338 		check_expr_assign(ln, szof);
   4339 		break;
   4340 	case CALL:
   4341 		check_expr_call(tn, ln, szof, vctx, cond, retval_discarded);
   4342 		break;
   4343 	case EQ:
   4344 		if (hflag && eqwarn)
   4345 			/* operator '==' found where '=' was expected */
   4346 			warning(160);
   4347 		break;
   4348 	case CON:
   4349 	case NAME:
   4350 	case STRING:
   4351 		return false;
   4352 	default:
   4353 		break;
   4354 	}
   4355 	return true;
   4356 }
   4357 
   4358 /*
   4359  *	vctx			???
   4360  *	cond			whether the expression is a condition that
   4361  *				will be compared with 0
   4362  *	eqwarn			whether the operator '==' might be a
   4363  *				misspelled '='
   4364  *	fcall			whether the expression is a function call
   4365  *	retval_discarded	whether the return value of a function call
   4366  *				is discarded; such calls will be analyzed by
   4367  *				lint2 in messages 4, 8 and 9
   4368  *	szof			whether the expression is part of a sizeof
   4369  *				expression, which means that its value is
   4370  *				discarded since only the type is relevant
   4371  */
   4372 void
   4373 check_expr_misc(const tnode_t *tn, bool vctx, bool cond,
   4374 		bool eqwarn, bool fcall, bool retval_discarded, bool szof)
   4375 {
   4376 	tnode_t *ln, *rn;
   4377 	const mod_t *mp;
   4378 	op_t op;
   4379 	bool cvctx, ccond, eq, discard;
   4380 
   4381 	if (tn == NULL)
   4382 		return;
   4383 
   4384 	ln = tn->tn_left;
   4385 	rn = tn->tn_right;
   4386 	mp = &modtab[op = tn->tn_op];
   4387 
   4388 	if (!check_expr_op(tn, op, ln,
   4389 	    szof, fcall, vctx, cond, retval_discarded, eqwarn))
   4390 		return;
   4391 
   4392 	cvctx = mp->m_value_context;
   4393 	ccond = mp->m_compares_with_zero;
   4394 	eq = mp->m_warn_if_operand_eq &&
   4395 	     !ln->tn_parenthesized &&
   4396 	     rn != NULL && !rn->tn_parenthesized;
   4397 
   4398 	/*
   4399 	 * values of operands of ':' are not used if the type of at least
   4400 	 * one of the operands (for gcc compatibility) is void
   4401 	 * XXX test/value context of QUEST should probably be used as
   4402 	 * context for both operands of COLON
   4403 	 */
   4404 	if (op == COLON && tn->tn_type->t_tspec == VOID)
   4405 		cvctx = ccond = false;
   4406 	discard = op == CVT && tn->tn_type->t_tspec == VOID;
   4407 	check_expr_misc(ln, cvctx, ccond, eq, op == CALL, discard, szof);
   4408 
   4409 	switch (op) {
   4410 	case PUSH:
   4411 		if (rn != NULL)
   4412 			check_expr_misc(rn, false, false, eq, false, false,
   4413 			    szof);
   4414 		break;
   4415 	case LOGAND:
   4416 	case LOGOR:
   4417 		check_expr_misc(rn, false, true, eq, false, false, szof);
   4418 		break;
   4419 	case COLON:
   4420 		check_expr_misc(rn, cvctx, ccond, eq, false, false, szof);
   4421 		break;
   4422 	case COMMA:
   4423 		check_expr_misc(rn, vctx, cond, false, false, false, szof);
   4424 		break;
   4425 	default:
   4426 		if (mp->m_binary)
   4427 			check_expr_misc(rn, true, false, eq, false, false,
   4428 			    szof);
   4429 		break;
   4430 	}
   4431 }
   4432 
   4433 /*
   4434  * Checks the range of array indices, if possible.
   4435  * amper is set if only the address of the element is used. This
   4436  * means that the index is allowed to refer to the first element
   4437  * after the array.
   4438  */
   4439 static void
   4440 check_array_index(tnode_t *tn, bool amper)
   4441 {
   4442 	int	dim;
   4443 	tnode_t	*ln, *rn;
   4444 	int	elsz;
   4445 	int64_t	con;
   4446 
   4447 	ln = tn->tn_left;
   4448 	rn = tn->tn_right;
   4449 
   4450 	/* We can only check constant indices. */
   4451 	if (rn->tn_op != CON)
   4452 		return;
   4453 
   4454 	/* Return if the left node does not stem from an array. */
   4455 	if (ln->tn_op != ADDR)
   4456 		return;
   4457 	if (ln->tn_left->tn_op != STRING && ln->tn_left->tn_op != NAME)
   4458 		return;
   4459 	if (ln->tn_left->tn_type->t_tspec != ARRAY)
   4460 		return;
   4461 
   4462 	/*
   4463 	 * For incomplete array types, we can print a warning only if
   4464 	 * the index is negative.
   4465 	 */
   4466 	if (is_incomplete(ln->tn_left->tn_type) && rn->tn_val->v_quad >= 0)
   4467 		return;
   4468 
   4469 	/* Get the size of one array element */
   4470 	if ((elsz = length_in_bits(ln->tn_type->t_subt, NULL)) == 0)
   4471 		return;
   4472 	elsz /= CHAR_SIZE;
   4473 
   4474 	/* Change the unit of the index from bytes to element size. */
   4475 	if (is_uinteger(rn->tn_type->t_tspec)) {
   4476 		con = (uint64_t)rn->tn_val->v_quad / elsz;
   4477 	} else {
   4478 		con = rn->tn_val->v_quad / elsz;
   4479 	}
   4480 
   4481 	dim = ln->tn_left->tn_type->t_dim + (amper ? 1 : 0);
   4482 
   4483 	if (!is_uinteger(rn->tn_type->t_tspec) && con < 0) {
   4484 		/* array subscript cannot be negative: %ld */
   4485 		warning(167, (long)con);
   4486 	} else if (dim > 0 && (uint64_t)con >= (uint64_t)dim) {
   4487 		/* array subscript cannot be > %d: %ld */
   4488 		warning(168, dim - 1, (long)con);
   4489 	}
   4490 }
   4491 
   4492 static bool
   4493 is_out_of_char_range(const tnode_t *tn)
   4494 {
   4495 	return tn->tn_op == CON &&
   4496 	       !(0 <= tn->tn_val->v_quad &&
   4497 		 tn->tn_val->v_quad < 1 << (CHAR_SIZE - 1));
   4498 }
   4499 
   4500 /*
   4501  * Check for ordered comparisons of unsigned values with 0.
   4502  */
   4503 static void
   4504 check_integer_comparison(op_t op, tnode_t *ln, tnode_t *rn)
   4505 {
   4506 	tspec_t	lt, rt;
   4507 
   4508 	lt = ln->tn_type->t_tspec;
   4509 	rt = rn->tn_type->t_tspec;
   4510 
   4511 	if (ln->tn_op != CON && rn->tn_op != CON)
   4512 		return;
   4513 
   4514 	if (!is_integer(lt) || !is_integer(rt))
   4515 		return;
   4516 
   4517 	if (hflag || pflag) {
   4518 		if (lt == CHAR && is_out_of_char_range(rn)) {
   4519 			/* nonportable character comparison '%s %d' */
   4520 			warning(230, op_name(op), (int)rn->tn_val->v_quad);
   4521 			return;
   4522 		}
   4523 		if (rt == CHAR && is_out_of_char_range(ln)) {
   4524 			/* nonportable character comparison '%s %d' */
   4525 			warning(230, op_name(op), (int)ln->tn_val->v_quad);
   4526 			return;
   4527 		}
   4528 	}
   4529 
   4530 	if (is_uinteger(lt) && !is_uinteger(rt) &&
   4531 	    rn->tn_op == CON && rn->tn_val->v_quad <= 0) {
   4532 		if (rn->tn_val->v_quad < 0) {
   4533 			/* comparison of %s with %s, op %s */
   4534 			warning(162, type_name(ln->tn_type),
   4535 			    "negative constant", op_name(op));
   4536 		} else if (op == LT || op == GE) {
   4537 			/* comparison of %s with %s, op %s */
   4538 			warning(162, type_name(ln->tn_type), "0", op_name(op));
   4539 		}
   4540 		return;
   4541 	}
   4542 	if (is_uinteger(rt) && !is_uinteger(lt) &&
   4543 	    ln->tn_op == CON && ln->tn_val->v_quad <= 0) {
   4544 		if (ln->tn_val->v_quad < 0) {
   4545 			/* comparison of %s with %s, op %s */
   4546 			warning(162, "negative constant",
   4547 			    type_name(rn->tn_type), op_name(op));
   4548 		} else if (op == GT || op == LE) {
   4549 			/* comparison of %s with %s, op %s */
   4550 			warning(162, "0", type_name(rn->tn_type), op_name(op));
   4551 		}
   4552 		return;
   4553 	}
   4554 }
   4555 
   4556 /*
   4557  * Return whether the expression can be used for static initialization.
   4558  *
   4559  * Constant initialization expressions must be constant or an address
   4560  * of a static object with an optional offset. In the first case,
   4561  * the result is returned in *offsp. In the second case, the static
   4562  * object is returned in *symp and the offset in *offsp.
   4563  *
   4564  * The expression can consist of PLUS, MINUS, ADDR, NAME, STRING and
   4565  * CON. Type conversions are allowed if they do not change binary
   4566  * representation (including width).
   4567  *
   4568  * C99 6.6 "Constant expressions"
   4569  * C99 6.7.8p4 restricts initializers for static storage duration
   4570  */
   4571 bool
   4572 constant_addr(const tnode_t *tn, const sym_t **symp, ptrdiff_t *offsp)
   4573 {
   4574 	const sym_t *sym;
   4575 	ptrdiff_t offs1, offs2;
   4576 	tspec_t	t, ot;
   4577 
   4578 	switch (tn->tn_op) {
   4579 	case MINUS:
   4580 		if (tn->tn_right->tn_op == CVT)
   4581 			return constant_addr(tn->tn_right, symp, offsp);
   4582 		else if (tn->tn_right->tn_op != CON)
   4583 			return false;
   4584 		/* FALLTHROUGH */
   4585 	case PLUS:
   4586 		offs1 = offs2 = 0;
   4587 		if (tn->tn_left->tn_op == CON) {
   4588 			offs1 = (ptrdiff_t)tn->tn_left->tn_val->v_quad;
   4589 			if (!constant_addr(tn->tn_right, &sym, &offs2))
   4590 				return false;
   4591 		} else if (tn->tn_right->tn_op == CON) {
   4592 			offs2 = (ptrdiff_t)tn->tn_right->tn_val->v_quad;
   4593 			if (tn->tn_op == MINUS)
   4594 				offs2 = -offs2;
   4595 			if (!constant_addr(tn->tn_left, &sym, &offs1))
   4596 				return false;
   4597 		} else {
   4598 			return false;
   4599 		}
   4600 		*symp = sym;
   4601 		*offsp = offs1 + offs2;
   4602 		return true;
   4603 	case ADDR:
   4604 		if (tn->tn_left->tn_op == NAME) {
   4605 			*symp = tn->tn_left->tn_sym;
   4606 			*offsp = 0;
   4607 			return true;
   4608 		} else {
   4609 			/*
   4610 			 * If this would be the front end of a compiler we
   4611 			 * would return a label instead of 0, at least if
   4612 			 * 'tn->tn_left->tn_op == STRING'.
   4613 			 */
   4614 			*symp = NULL;
   4615 			*offsp = 0;
   4616 			return true;
   4617 		}
   4618 	case CVT:
   4619 		t = tn->tn_type->t_tspec;
   4620 		ot = tn->tn_left->tn_type->t_tspec;
   4621 		if ((!is_integer(t) && t != PTR) ||
   4622 		    (!is_integer(ot) && ot != PTR)) {
   4623 			return false;
   4624 		}
   4625 #if 0
   4626 		/*
   4627 		 * consider:
   4628 		 *	struct foo {
   4629 		 *		unsigned char a;
   4630 		 *	} f = {
   4631 		 *		(unsigned char)(unsigned long)
   4632 		 *		    (&(((struct foo *)0)->a))
   4633 		 *	};
   4634 		 * since psize(unsigned long) != psize(unsigned char),
   4635 		 * this fails.
   4636 		 */
   4637 		else if (psize(t) != psize(ot))
   4638 			return -1;
   4639 #endif
   4640 		return constant_addr(tn->tn_left, symp, offsp);
   4641 	default:
   4642 		return false;
   4643 	}
   4644 }
   4645 
   4646 /* Append s2 to s1, then free s2. */
   4647 strg_t *
   4648 cat_strings(strg_t *s1, strg_t *s2)
   4649 {
   4650 
   4651 	if (s1->st_char != s2->st_char) {
   4652 		/* cannot concatenate wide and regular string literals */
   4653 		error(292);
   4654 		return s1;
   4655 	}
   4656 
   4657 	size_t len1 = s1->st_len;
   4658 	size_t len2 = s2->st_len;
   4659 	size_t chsize = s1->st_char ? sizeof(char) : sizeof(wchar_t);
   4660 	size_t size1 = len1 * chsize;
   4661 	size_t size2 = (len2 + 1) * chsize;
   4662 	s1->st_mem = xrealloc(s1->st_mem, size1 + size2);
   4663 	memcpy((char *)s1->st_mem + size1, s2->st_mem, size2);
   4664 	free(s2->st_mem);
   4665 
   4666 	s1->st_len = len1 + len2;
   4667 	free(s2);
   4668 
   4669 	return s1;
   4670 }
   4671 
   4672 static bool
   4673 is_confusing_precedence(op_t op, op_t lop, bool lparen, op_t rop, bool rparen)
   4674 {
   4675 
   4676 	if (op == SHL || op == SHR) {
   4677 		if (!lparen && (lop == PLUS || lop == MINUS))
   4678 			return true;
   4679 		if (!rparen && (rop == PLUS || rop == MINUS))
   4680 			return true;
   4681 		return false;
   4682 	}
   4683 
   4684 	if (op == LOGOR) {
   4685 		if (!lparen && lop == LOGAND)
   4686 			return true;
   4687 		if (!rparen && rop == LOGAND)
   4688 			return true;
   4689 		return false;
   4690 	}
   4691 
   4692 	lint_assert(op == BITAND || op == BITXOR || op == BITOR);
   4693 	if (!lparen && lop != op) {
   4694 		if (lop == PLUS || lop == MINUS)
   4695 			return true;
   4696 		if (lop == BITAND || lop == BITXOR)
   4697 			return true;
   4698 	}
   4699 	if (!rparen && rop != op) {
   4700 		if (rop == PLUS || rop == MINUS)
   4701 			return true;
   4702 		if (rop == BITAND || rop == BITXOR)
   4703 			return true;
   4704 	}
   4705 	return false;
   4706 }
   4707 
   4708 /*
   4709  * Print a warning if the given node has operands which should be
   4710  * parenthesized.
   4711  *
   4712  * XXX Does not work if an operand is a constant expression. Constant
   4713  * expressions are already folded.
   4714  */
   4715 static void
   4716 check_precedence_confusion(tnode_t *tn)
   4717 {
   4718 	tnode_t *ln, *rn;
   4719 
   4720 	if (!hflag)
   4721 		return;
   4722 
   4723 	debug_node(tn);
   4724 
   4725 	lint_assert(is_binary(tn));
   4726 	for (ln = tn->tn_left; ln->tn_op == CVT; ln = ln->tn_left)
   4727 		continue;
   4728 	for (rn = tn->tn_right; rn->tn_op == CVT; rn = rn->tn_left)
   4729 		continue;
   4730 
   4731 	if (is_confusing_precedence(tn->tn_op,
   4732 	    ln->tn_op, ln->tn_parenthesized,
   4733 	    rn->tn_op, rn->tn_parenthesized)) {
   4734 		/* precedence confusion possible: parenthesize! */
   4735 		warning(169);
   4736 	}
   4737 }
   4738 
   4739 typedef struct stmt_expr {
   4740 	struct memory_block *se_mem;
   4741 	sym_t *se_sym;
   4742 	struct stmt_expr *se_enclosing;
   4743 } stmt_expr;
   4744 
   4745 static stmt_expr *stmt_exprs;
   4746 
   4747 void
   4748 begin_statement_expr(void)
   4749 {
   4750 	stmt_expr *se = xmalloc(sizeof(*se));
   4751 	se->se_mem = expr_save_memory();
   4752 	se->se_sym = NULL;
   4753 	se->se_enclosing = stmt_exprs;
   4754 	stmt_exprs = se;
   4755 }
   4756 
   4757 void
   4758 do_statement_expr(tnode_t *tn)
   4759 {
   4760 	block_level--;
   4761 	mem_block_level--;
   4762 	stmt_exprs->se_sym = tn != NULL
   4763 	    ? mktempsym(block_dup_type(tn->tn_type))
   4764 	    : NULL;		/* after a syntax error */
   4765 	mem_block_level++;
   4766 	block_level++;
   4767 	/* ({ }) is a GCC extension */
   4768 	gnuism(320);
   4769 }
   4770 
   4771 tnode_t *
   4772 end_statement_expr(void)
   4773 {
   4774 	stmt_expr *se = stmt_exprs;
   4775 	if (se->se_sym == NULL)
   4776 		return NULL;	/* after a syntax error */
   4777 	tnode_t *tn = build_name(se->se_sym, false);
   4778 	(void)expr_save_memory();	/* leak */
   4779 	expr_restore_memory(se->se_mem);
   4780 	stmt_exprs = se->se_enclosing;
   4781 	free(se);
   4782 	return tn;
   4783 }
   4784