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expr_sizeof.c revision 1.9
      1  1.9  rillig /*	$NetBSD: expr_sizeof.c,v 1.9 2023/06/30 09:21:52 rillig Exp $	*/
      2  1.1  rillig # 3 "expr_sizeof.c"
      3  1.1  rillig 
      4  1.1  rillig /*
      5  1.1  rillig  * C99 6.5.3.4 "The sizeof operator"
      6  1.1  rillig  * C11 6.5.3.4 "The sizeof operator"
      7  1.1  rillig  */
      8  1.1  rillig 
      9  1.5  rillig /* lint1-extra-flags: -X 351 */
     10  1.5  rillig 
     11  1.1  rillig /*
     12  1.1  rillig  * A sizeof expression can either take a type name or an expression.
     13  1.1  rillig  */
     14  1.1  rillig void sink(unsigned long);
     15  1.1  rillig 
     16  1.1  rillig struct {
     17  1.1  rillig 	int member;
     18  1.1  rillig } s, *ps;
     19  1.1  rillig 
     20  1.1  rillig /*
     21  1.1  rillig  * In a sizeof expression taking a type name, the type name must be enclosed
     22  1.1  rillig  * in parentheses.
     23  1.1  rillig  */
     24  1.1  rillig /* expect+1: error: negative array dimension (-4) [20] */
     25  1.1  rillig typedef int sizeof_int[-(int)sizeof(int)];
     26  1.1  rillig 
     27  1.1  rillig /*
     28  1.1  rillig  * In a sizeof expression taking an expression, the expression may or may not
     29  1.1  rillig  * be enclosed in parentheses, like any other expression.
     30  1.1  rillig  */
     31  1.1  rillig /* expect+1: error: negative array dimension (-4) [20] */
     32  1.1  rillig typedef int sizeof_paren_zero[-(int)sizeof(0)];
     33  1.1  rillig /* expect+1: error: negative array dimension (-4) [20] */
     34  1.1  rillig typedef int sizeof_zero[-(int)sizeof 0];
     35  1.1  rillig 
     36  1.1  rillig /*
     37  1.1  rillig  * Even though 's' is not a constant expression, 'sizeof s' is.
     38  1.1  rillig  */
     39  1.1  rillig /* expect+1: error: negative array dimension (-4) [20] */
     40  1.1  rillig typedef int sizeof_global_var[-(int)sizeof s];
     41  1.1  rillig /* expect+1: error: negative array dimension (-4) [20] */
     42  1.1  rillig typedef int sizeof_paren_global_var[-(int)sizeof(s)];
     43  1.1  rillig 
     44  1.1  rillig /*
     45  1.1  rillig  * Even though 'sizeof(s)' may look like a function call expression, the
     46  1.1  rillig  * parentheses around 's' are ordinary parentheses and do not influence the
     47  1.2  rillig  * precedence.
     48  1.2  rillig  *
     49  1.2  rillig  * Therefore, the '.' following the '(s)' takes precedence over the 'sizeof'.
     50  1.2  rillig  * Same for the '->' following the '(ps)'.  Same for the '[0]' following the
     51  1.2  rillig  * '(arr)'.
     52  1.1  rillig  */
     53  1.1  rillig /* expect+1: error: negative array dimension (-4) [20] */
     54  1.1  rillig typedef int sizeof_paren_global_struct_member[-(int)sizeof(s).member];
     55  1.1  rillig /* expect+1: error: negative array dimension (-4) [20] */
     56  1.1  rillig typedef int sizeof_paren_global_ptr_struct_member[-(int)sizeof(ps)->member];
     57  1.2  rillig int arr[] = { 1, 2, 3 };
     58  1.2  rillig /* expect+1: error: negative array dimension (-3) [20] */
     59  1.2  rillig typedef int arr_count[-(int)sizeof(arr) / (int)sizeof(arr)[0]];
     60  1.2  rillig 
     61  1.2  rillig /* FIXME: 'n' is actually used, for the variable length array. */
     62  1.2  rillig /* expect+2: warning: argument 'n' unused in function 'variable_length_array' [231] */
     63  1.2  rillig void
     64  1.2  rillig variable_length_array(int n)
     65  1.2  rillig {
     66  1.2  rillig 	int local_arr[n + 5];
     67  1.3  rillig 
     68  1.3  rillig 	/*
     69  1.3  rillig 	 * Since the array length is not constant, it cannot be used in a
     70  1.4  rillig 	 * typedef.  Code like this is already rejected by the compiler.  For
     71  1.3  rillig 	 * simplicity, lint assumes that the array has length 1.
     72  1.3  rillig 	 */
     73  1.2  rillig 	/* expect+1: error: negative array dimension (-4) [20] */
     74  1.2  rillig 	typedef int sizeof_local_arr[-(int)sizeof(local_arr)];
     75  1.2  rillig }
     76  1.6  rillig 
     77  1.7  rillig void
     78  1.7  rillig bit_fields(void)
     79  1.7  rillig {
     80  1.7  rillig 	struct {
     81  1.7  rillig 		_Bool flag0:1;
     82  1.7  rillig 		_Bool flag1:1;
     83  1.7  rillig 		_Bool flag2:1;
     84  1.7  rillig 	} flags;
     85  1.7  rillig 	/* expect+1: error: negative array dimension (-1) [20] */
     86  1.7  rillig 	typedef int sizeof_flags[-(int)sizeof(flags)];
     87  1.7  rillig 
     88  1.7  rillig 	struct {
     89  1.7  rillig 		struct {
     90  1.7  rillig 			_Bool flag0:1;
     91  1.7  rillig 			_Bool flag1:1;
     92  1.7  rillig 			_Bool flag2:1;
     93  1.7  rillig 		};
     94  1.7  rillig 	} anonymous_flags;
     95  1.7  rillig 	/* FIXME: sizeof must be 1, not 0. */
     96  1.7  rillig 	typedef int sizeof_anonymous_flags[-(int)sizeof(anonymous_flags)];
     97  1.7  rillig 
     98  1.7  rillig 	struct {
     99  1.7  rillig 		unsigned int bits0:16;
    100  1.7  rillig 		unsigned int bits1:16;
    101  1.7  rillig 	} same_storage_unit;
    102  1.7  rillig 	/* expect+1: error: negative array dimension (-4) [20] */
    103  1.7  rillig 	typedef int sizeof_same_storage_unit[-(int)sizeof(same_storage_unit)];
    104  1.7  rillig 
    105  1.7  rillig 	// Detect whether a bit-field can span multiple storage units.
    106  1.7  rillig 	// If so, the size is 12, if not, the size is 16.
    107  1.7  rillig 	struct {
    108  1.7  rillig 		unsigned int bits0:24;
    109  1.7  rillig 		unsigned int bits1:24;
    110  1.7  rillig 		unsigned int bits2:24;
    111  1.7  rillig 		unsigned int bits3:24;
    112  1.7  rillig 	} cross_storage_unit;
    113  1.7  rillig 	/* expect+1: error: negative array dimension (-16) [20] */
    114  1.7  rillig 	typedef int sizeof_cross_storage_unit[-(int)sizeof(cross_storage_unit)];
    115  1.8  rillig 
    116  1.8  rillig 	/*
    117  1.8  rillig 	 * The bit-fields in a struct may be merged into the same storage
    118  1.8  rillig 	 * units, even if their types differ. GCC 10, Clang 15 and lint all
    119  1.9  rillig 	 * agree in packing the first group of bit-fields and the char into
    120  1.9  rillig 	 * 4 bytes, even though their underlying types differ.  The second
    121  1.9  rillig 	 * group of bit-fields gets its own storage unit.
    122  1.8  rillig 	 */
    123  1.8  rillig 	struct mixed {
    124  1.8  rillig 		_Bool flag0:1;
    125  1.8  rillig 		signed int signed0:1;
    126  1.8  rillig 		unsigned int unsigned0:1;
    127  1.9  rillig 		char ch[3];
    128  1.8  rillig 		_Bool flag1:1;
    129  1.8  rillig 		signed int signed1:1;
    130  1.8  rillig 		unsigned int unsigned1:1;
    131  1.8  rillig 	} mixed;
    132  1.9  rillig 	/* expect+1: error: negative array dimension (-8) [20] */
    133  1.8  rillig 	typedef int sizeof_mixed[-(int)sizeof(mixed)];
    134  1.8  rillig 	/* FIXME: Implement build_offsetof correctly. */
    135  1.9  rillig 	/* expect+3: error: negative array dimension (-8) [20] */
    136  1.8  rillig 	typedef int offsetof_mixed_ch[
    137  1.8  rillig 	    -(int)__builtin_offsetof(struct mixed, ch)
    138  1.8  rillig 	];
    139  1.7  rillig }
    140  1.7  rillig 
    141  1.6  rillig /*
    142  1.6  rillig  * Ensure that anonymous structs and unions are handled correctly.  They were
    143  1.6  rillig  * added in C11, and lint did not properly support them until 2023.
    144  1.6  rillig  */
    145  1.6  rillig void
    146  1.6  rillig anonymous_struct_and_union(void)
    147  1.6  rillig {
    148  1.6  rillig 	struct {
    149  1.6  rillig 		union {
    150  1.6  rillig 			unsigned char uc16[16];
    151  1.6  rillig 			unsigned char uc32[32];
    152  1.6  rillig 		};
    153  1.6  rillig 	} su_16_32;
    154  1.6  rillig 	/* FIXME: Must be 32, not 48. */
    155  1.6  rillig 	/* expect+1: error: negative array dimension (-48) [20] */
    156  1.6  rillig 	typedef int sizeof_su_16_32[-(int)sizeof(su_16_32)];
    157  1.6  rillig 
    158  1.6  rillig 	union {
    159  1.6  rillig 		struct {
    160  1.6  rillig 			unsigned char uc16[16];
    161  1.6  rillig 			unsigned char uc32[32];
    162  1.6  rillig 		};
    163  1.6  rillig 	} us_16_32;
    164  1.6  rillig 	/* expect+1: error: negative array dimension (-48) [20] */
    165  1.6  rillig 	typedef int sizeof_us_16_32[-(int)sizeof(us_16_32)];
    166  1.6  rillig }
    167