xref: /src/usr.bin/make/for.c

/*	$NetBSD: for.c,v 1.118 2020/12/15 16:24:17 rillig Exp $	*/

/*
 * Copyright (c) 1992, The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*-
 * Handling of .for/.endfor loops in a makefile.
 *
 * For loops are of the form:
 *
 * .for <varname...> in <value...>
 * ...
 * .endfor
 *
 * When a .for line is parsed, all following lines are accumulated into a
 * buffer, up to but excluding the corresponding .endfor line.  To find the
 * corresponding .endfor, the number of nested .for and .endfor directives
 * are counted.
 *
 * During parsing, any nested .for loops are just passed through; they get
 * handled recursively in For_Eval when the enclosing .for loop is evaluated
 * in For_Run.
 *
 * When the .for loop has been parsed completely, the variable expressions
 * for the iteration variables are replaced with expressions of the form
 * ${:Uvalue}, and then this modified body is "included" as a special file.
 *
 * Interface:
 *	For_Eval	Evaluate the loop in the passed line.
 *
 *	For_Run		Run accumulated loop
 */

#include "make.h"

/*	"@(#)for.c	8.1 (Berkeley) 6/6/93"	*/
MAKE_RCSID("$NetBSD: for.c,v 1.118 2020/12/15 16:24:17 rillig Exp $");

static int forLevel = 0;	/* Nesting level */

/* One of the variables to the left of the "in" in a .for loop. */
typedef struct ForVar {
	char *name;
	size_t len;
} ForVar;

/*
 * State of a for loop.
 */
typedef struct For {
	Buffer body;		/* Unexpanded body of the loop */
	Vector /* of ForVar */ vars; /* Iteration variables */
	Words items;		/* Substitution items */
	Buffer curBody;		/* Expanded body of the current iteration */
	/* Is any of the names 1 character long? If so, when the variable values
	 * are substituted, the parser must handle $V expressions as well, not
	 * only ${V} and $(V). */
	Boolean short_var;
	unsigned int sub_next;	/* Where to continue iterating */
} For;

static For *accumFor;		/* Loop being accumulated */

static void
ForAddVar(For *f, const char *name, size_t len)
{
	ForVar *var = Vector_Push(&f->vars);
	var->name = bmake_strldup(name, len);
	var->len = len;
}

static void
For_Free(For *f)
{
	Buf_Destroy(&f->body, TRUE);

	while (f->vars.len > 0) {
		ForVar *var = Vector_Pop(&f->vars);
		free(var->name);
	}
	Vector_Done(&f->vars);

	Words_Free(f->items);
	Buf_Destroy(&f->curBody, TRUE);

	free(f);
}

static Boolean
IsFor(const char *p)
{
	return p[0] == 'f' && p[1] == 'o' && p[2] == 'r' && ch_isspace(p[3]);
}

static Boolean
IsEndfor(const char *p)
{
	return p[0] == 'e' && strncmp(p, "endfor", 6) == 0 &&
	       (p[6] == '\0' || ch_isspace(p[6]));
}

/* Evaluate the for loop in the passed line. The line looks like this:
 *	.for <varname...> in <value...>
 *
 * Input:
 *	line		Line to parse
 *
 * Results:
 *      0: Not a .for statement, parse the line
 *	1: We found a for loop
 *     -1: A .for statement with a bad syntax error, discard.
 */
int
For_Eval(const char *line)
{
	For *f;
	const char *p;

	p = line + 1;		/* skip the '.' */
	cpp_skip_whitespace(&p);

	if (!IsFor(p)) {
		if (IsEndfor(p)) {
			Parse_Error(PARSE_FATAL, "for-less endfor");
			return -1;
		}
		return 0;
	}
	p += 3;

	/*
	 * we found a for loop, and now we are going to parse it.
	 */

	f = bmake_malloc(sizeof *f);
	Buf_Init(&f->body);
	Vector_Init(&f->vars, sizeof(ForVar));
	f->items.words = NULL;
	f->items.freeIt = NULL;
	Buf_Init(&f->curBody);
	f->short_var = FALSE;
	f->sub_next = 0;

	/* Grab the variables. Terminate on "in". */
	for (;;) {
		size_t len;

		cpp_skip_whitespace(&p);
		if (*p == '\0') {
			Parse_Error(PARSE_FATAL, "missing `in' in for");
			For_Free(f);
			return -1;
		}

		/*
		 * XXX: This allows arbitrary variable names;
		 * see directive-for.mk.
		 */
		for (len = 1; p[len] != '\0' && !ch_isspace(p[len]); len++)
			continue;

		if (len == 2 && p[0] == 'i' && p[1] == 'n') {
			p += 2;
			break;
		}
		if (len == 1)
			f->short_var = TRUE;

		ForAddVar(f, p, len);
		p += len;
	}

	if (f->vars.len == 0) {
		Parse_Error(PARSE_FATAL, "no iteration variables in for");
		For_Free(f);
		return -1;
	}

	cpp_skip_whitespace(&p);

	{
		char *items;
		(void)Var_Subst(p, VAR_GLOBAL, VARE_WANTRES, &items);
		/* TODO: handle errors */
		f->items = Str_Words(items, FALSE);
		free(items);

		if (f->items.len == 1 && f->items.words[0][0] == '\0')
			f->items.len = 0; /* .for var in ${:U} */
	}

	{
		size_t nitems, nvars;

		if ((nitems = f->items.len) > 0 &&
		    nitems % (nvars = f->vars.len)) {
			Parse_Error(PARSE_FATAL,
			    "Wrong number of words (%u) in .for "
			    "substitution list with %u variables",
			    (unsigned)nitems, (unsigned)nvars);
			/*
			 * Return 'success' so that the body of the .for loop
			 * is accumulated.
			 * Remove all items so that the loop doesn't iterate.
			 */
			f->items.len = 0;
		}
	}

	accumFor = f;
	forLevel = 1;
	return 1;
}

/*
 * Add another line to a .for loop.
 * Returns FALSE when the matching .endfor is reached.
 */
Boolean
For_Accum(const char *line)
{
	const char *ptr = line;

	if (*ptr == '.') {
		ptr++;
		cpp_skip_whitespace(&ptr);

		if (IsEndfor(ptr)) {
			DEBUG1(FOR, "For: end for %d\n", forLevel);
			if (--forLevel <= 0)
				return FALSE;
		} else if (IsFor(ptr)) {
			forLevel++;
			DEBUG1(FOR, "For: new loop %d\n", forLevel);
		}
	}

	Buf_AddStr(&accumFor->body, line);
	Buf_AddByte(&accumFor->body, '\n');
	return TRUE;
}


static size_t
for_var_len(const char *var)
{
	char ch, var_start, var_end;
	int depth;
	size_t len;

	var_start = *var;
	if (var_start == '\0')
		/* just escape the $ */
		return 0;

	if (var_start == '(')
		var_end = ')';
	else if (var_start == '{')
		var_end = '}';
	else
		return 1;	/* Single char variable */

	depth = 1;
	for (len = 1; (ch = var[len++]) != '\0';) {
		if (ch == var_start)
			depth++;
		else if (ch == var_end && --depth == 0)
			return len;
	}

	/* Variable end not found, escape the $ */
	return 0;
}

/* The .for loop substitutes the items as ${:U<value>...}, which means
 * that characters that break this syntax must be backslash-escaped. */
static Boolean
NeedsEscapes(const char *word, char endc)
{
	const char *p;

	for (p = word; *p != '\0'; p++) {
		if (*p == ':' || *p == '$' || *p == '\\' || *p == endc)
			return TRUE;
	}
	return FALSE;
}

/* While expanding the body of a .for loop, write the item in the ${:U...}
 * expression, escaping characters as needed.
 *
 * The result is later unescaped by ApplyModifier_Defined. */
static void
Buf_AddEscaped(Buffer *cmds, const char *item, char ech)
{
	char ch;

	if (!NeedsEscapes(item, ech)) {
		Buf_AddStr(cmds, item);
		return;
	}

	/* Escape ':', '$', '\\' and 'ech' - these will be removed later by
	 * :U processing, see ApplyModifier_Defined. */
	while ((ch = *item++) != '\0') {
		if (ch == '$') {
			size_t len = for_var_len(item);
			if (len != 0) {
				Buf_AddBytes(cmds, item - 1, len + 1);
				item += len;
				continue;
			}
			Buf_AddByte(cmds, '\\');
		} else if (ch == ':' || ch == '\\' || ch == ech)
			Buf_AddByte(cmds, '\\');
		Buf_AddByte(cmds, ch);
	}
}

/* While expanding the body of a .for loop, replace expressions like
 * ${i}, ${i:...}, $(i) or $(i:...) with their ${:U...} expansion. */
static void
SubstVarLong(For *f, const char **pp, const char **inout_mark, char ech)
{
	size_t i;
	const char *p = *pp;

	for (i = 0; i < f->vars.len; i++) {
		ForVar *forVar = Vector_Get(&f->vars, i);
		char *var = forVar->name;
		size_t vlen = forVar->len;

		/* XXX: undefined behavior for p if vlen is longer than p? */
		if (memcmp(p, var, vlen) != 0)
			continue;
		/* XXX: why test for backslash here? */
		if (p[vlen] != ':' && p[vlen] != ech && p[vlen] != '\\')
			continue;

		/* Found a variable match. Replace with :U<value> */
		Buf_AddBytesBetween(&f->curBody, *inout_mark, p);
		Buf_AddStr(&f->curBody, ":U");
		Buf_AddEscaped(&f->curBody,
		    f->items.words[f->sub_next + i], ech);

		p += vlen;
		*inout_mark = p;
		break;
	}

	*pp = p;
}

/* While expanding the body of a .for loop, replace single-character
 * variable expressions like $i with their ${:U...} expansion. */
static void
SubstVarShort(For *f, char ch, const char **pp, const char **inout_mark)
{
	const char *p = *pp;
	size_t i;

	/* Probably a single character name, ignore $$ and stupid ones. */
	if (!f->short_var || strchr("}):$", ch) != NULL) {
		p++;
		*pp = p;
		return;
	}

	for (i = 0; i < f->vars.len; i++) {
		ForVar *var = Vector_Get(&f->vars, i);
		const char *varname = var->name;
		if (varname[0] != ch || varname[1] != '\0')
			continue;

		/* Found a variable match. Replace with ${:U<value>} */
		Buf_AddBytesBetween(&f->curBody, *inout_mark, p);
		Buf_AddStr(&f->curBody, "{:U");
		Buf_AddEscaped(&f->curBody,
		    f->items.words[f->sub_next + i], '}');
		Buf_AddByte(&f->curBody, '}');

		*inout_mark = ++p;
		break;
	}

	*pp = p;
}

/*
 * Scan the for loop body and replace references to the loop variables
 * with variable references that expand to the required text.
 *
 * Using variable expansions ensures that the .for loop can't generate
 * syntax, and that the later parsing will still see a variable.
 * We assume that the null variable will never be defined.
 *
 * The detection of substitutions of the loop control variable is naive.
 * Many of the modifiers use \ to escape $ (not $) so it is possible
 * to contrive a makefile where an unwanted substitution happens.
 */
static char *
ForIterate(void *v_arg, size_t *out_len)
{
	For *f = v_arg;
	const char *p;
	const char *mark;	/* where the last replacement left off */
	const char *body_end;
	char *cmds_str;

	if (f->sub_next + f->vars.len > f->items.len) {
		/* No more iterations */
		For_Free(f);
		return NULL;
	}

	Buf_Empty(&f->curBody);

	mark = Buf_GetAll(&f->body, NULL);
	body_end = mark + Buf_Len(&f->body);
	for (p = mark; (p = strchr(p, '$')) != NULL;) {
		char ch, ech;
		ch = *++p;
		if ((ch == '(' && (ech = ')', 1)) ||
		    (ch == '{' && (ech = '}', 1))) {
			p++;
			SubstVarLong(f, &p, &mark, ech);
			continue;
		}
		if (ch == '\0')
			break;

		SubstVarShort(f, ch, &p, &mark);
	}
	Buf_AddBytesBetween(&f->curBody, mark, body_end);

	*out_len = Buf_Len(&f->curBody);
	cmds_str = Buf_GetAll(&f->curBody, NULL);
	DEBUG1(FOR, "For: loop body:\n%s", cmds_str);

	f->sub_next += f->vars.len;

	return cmds_str;
}

/* Run the for loop, imitating the actions of an include file. */
void
For_Run(int lineno)
{
	For *f = accumFor;
	accumFor = NULL;

	if (f->items.len == 0) {
		/*
		 * Nothing to expand - possibly due to an earlier syntax
		 * error.
		 */
		For_Free(f);
		return;
	}

	Parse_SetInput(NULL, lineno, -1, ForIterate, f);
}