1
/*
2
 * "Optimize" a list of dependencies as spit out by gcc -MD
3
 * for the kernel build
4
 * ===========================================================================
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 *
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 * Author       Kai Germaschewski
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 * Copyright    2002 by Kai Germaschewski  <[email protected]>
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 *
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 * This software may be used and distributed according to the terms
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 * of the GNU General Public License, incorporated herein by reference.
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 *
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 *
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 * Introduction:
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 *
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 * gcc produces a very nice and correct list of dependencies which
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 * tells make when to remake a file.
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 *
18
 * To use this list as-is however has the drawback that virtually
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 * every file in the kernel includes autoconf.h.
20
 *
21
 * If the user re-runs make *config, autoconf.h will be
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 * regenerated.  make notices that and will rebuild every file which
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 * includes autoconf.h, i.e. basically all files. This is extremely
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 * annoying if the user just changed CONFIG_HIS_DRIVER from n to m.
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 *
26
 * So we play the same trick that "mkdep" played before. We replace
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 * the dependency on autoconf.h by a dependency on every config
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 * option which is mentioned in any of the listed prerequisites.
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 *
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 * kconfig populates a tree in include/config/ with an empty file
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 * for each config symbol and when the configuration is updated
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 * the files representing changed config options are touched
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 * which then let make pick up the changes and the files that use
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 * the config symbols are rebuilt.
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 *
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 * So if the user changes his CONFIG_HIS_DRIVER option, only the objects
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 * which depend on "include/config/HIS_DRIVER" will be rebuilt,
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 * so most likely only his driver ;-)
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 *
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 * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
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 *
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 * So to get dependencies right, there are two issues:
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 * o if any of the files the compiler read changed, we need to rebuild
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 * o if the command line given to the compile the file changed, we
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 *   better rebuild as well.
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 *
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 * The former is handled by using the -MD output, the later by saving
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 * the command line used to compile the old object and comparing it
49
 * to the one we would now use.
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 *
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 * Again, also this idea is pretty old and has been discussed on
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 * kbuild-devel a long time ago. I don't have a sensibly working
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 * internet connection right now, so I rather don't mention names
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 * without double checking.
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 *
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 * This code here has been based partially based on mkdep.c, which
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 * says the following about its history:
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 *
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 *   Copyright abandoned, Michael Chastain, <mailto:[email protected]>.
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 *   This is a C version of syncdep.pl by Werner Almesberger.
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 *
62
 *
63
 * It is invoked as
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 *
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 *   fixdep <depfile> <target> <cmdline>
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 *
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 * and will read the dependency file <depfile>
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 *
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 * The transformed dependency snipped is written to stdout.
70
 *
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 * It first generates a line
72
 *
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 *   savedcmd_<target> = <cmdline>
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 *
75
 * and then basically copies the .<target>.d file to stdout, in the
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 * process filtering out the dependency on autoconf.h and adding
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 * dependencies on include/config/MY_OPTION for every
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 * CONFIG_MY_OPTION encountered in any of the prerequisites.
79
 *
80
 * We don't even try to really parse the header files, but
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 * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
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 * be picked up as well. It's not a problem with respect to
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 * correctness, since that can only give too many dependencies, thus
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 * we cannot miss a rebuild. Since people tend to not mention totally
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 * unrelated CONFIG_ options all over the place, it's not an
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 * efficiency problem either.
87
 *
88
 * (Note: it'd be easy to port over the complete mkdep state machine,
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 *  but I don't think the added complexity is worth it)
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 */
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92
#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <string.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <stdio.h>
100
#include <ctype.h>
101

102
static void usage(void)
103
{
104
	fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
105
	exit(1);
106
}
107

108
struct item {
109
	struct item	*next;
110
	unsigned int	len;
111
	unsigned int	hash;
112
	char		name[];
113
};
114

115
#define HASHSZ 256
116
static struct item *config_hashtab[HASHSZ], *file_hashtab[HASHSZ];
117

118
static unsigned int strhash(const char *str, unsigned int sz)
119
{
120
	/* fnv32 hash */
121
	unsigned int i, hash = 2166136261U;
122

123
	for (i = 0; i < sz; i++)
124
		hash = (hash ^ str[i]) * 0x01000193;
125
	return hash;
126
}
127

128
/*
129
 * Add a new value to the configuration string.
130
 */
131
static void add_to_hashtable(const char *name, int len, unsigned int hash,
132
			     struct item *hashtab[])
133
{
134
	struct item *aux = malloc(sizeof(*aux) + len);
135

136
	if (!aux) {
137
		perror("fixdep:malloc");
138
		exit(1);
139
	}
140
	memcpy(aux->name, name, len);
141
	aux->len = len;
142
	aux->hash = hash;
143
	aux->next = hashtab[hash % HASHSZ];
144
	hashtab[hash % HASHSZ] = aux;
145
}
146

147
/*
148
 * Lookup a string in the hash table. If found, just return true.
149
 * If not, add it to the hashtable and return false.
150
 */
151
static bool in_hashtable(const char *name, int len, struct item *hashtab[])
152
{
153
	struct item *aux;
154
	unsigned int hash = strhash(name, len);
155

156
	for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
157
		if (aux->hash == hash && aux->len == len &&
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		    memcmp(aux->name, name, len) == 0)
159
			return true;
160
	}
161

162
	add_to_hashtable(name, len, hash, hashtab);
163

164
	return false;
165
}
166

167
/*
168
 * Record the use of a CONFIG_* word.
169
 */
170
static void use_config(const char *m, int slen)
171
{
172
	if (in_hashtable(m, slen, config_hashtab))
173
		return;
174

175
	/* Print out a dependency path from a symbol name. */
176
	printf("    $(wildcard include/config/%.*s) \\\n", slen, m);
177
}
178

179
/* test if s ends in sub */
180
static int str_ends_with(const char *s, int slen, const char *sub)
181
{
182
	int sublen = strlen(sub);
183

184
	if (sublen > slen)
185
		return 0;
186

187
	return !memcmp(s + slen - sublen, sub, sublen);
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}
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190
static void parse_config_file(const char *p)
191
{
192
	const char *q, *r;
193
	const char *start = p;
194

195
	while ((p = strstr(p, "CONFIG_"))) {
196
		if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
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			p += 7;
198
			continue;
199
		}
200
		p += 7;
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		q = p;
202
		while (isalnum(*q) || *q == '_')
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			q++;
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		if (str_ends_with(p, q - p, "_MODULE"))
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			r = q - 7;
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		else
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			r = q;
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		if (r > p)
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			use_config(p, r - p);
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		p = q;
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	}
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}
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214
static void *read_file(const char *filename)
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{
216
	struct stat st;
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	int fd;
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	char *buf;
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220
	fd = open(filename, O_RDONLY);
221
	if (fd < 0) {
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		fprintf(stderr, "fixdep: error opening file: ");
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		perror(filename);
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		exit(2);
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	}
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	if (fstat(fd, &st) < 0) {
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		fprintf(stderr, "fixdep: error fstat'ing file: ");
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		perror(filename);
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		exit(2);
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	}
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	buf = malloc(st.st_size + 1);
232
	if (!buf) {
233
		perror("fixdep: malloc");
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		exit(2);
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	}
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	if (read(fd, buf, st.st_size) != st.st_size) {
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		perror("fixdep: read");
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		exit(2);
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	}
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	buf[st.st_size] = '\0';
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	close(fd);
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243
	return buf;
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}
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246
/* Ignore certain dependencies */
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static int is_ignored_file(const char *s, int len)
248
{
249
	return str_ends_with(s, len, "include/generated/autoconf.h");
250
}
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252
/* Do not parse these files */
253
static int is_no_parse_file(const char *s, int len)
254
{
255
	/* rustc may list binary files in dep-info */
256
	return str_ends_with(s, len, ".rlib") ||
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	       str_ends_with(s, len, ".rmeta") ||
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	       str_ends_with(s, len, ".so");
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}
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261
/*
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 * Important: The below generated source_foo.o and deps_foo.o variable
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 * assignments are parsed not only by make, but also by the rather simple
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 * parser in scripts/mod/sumversion.c.
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 */
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static void parse_dep_file(char *p, const char *target)
267
{
268
	bool saw_any_target = false;
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	bool is_target = true;
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	bool is_source = false;
271
	bool need_parse;
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	char *q, saved_c;
273

274
	while (*p) {
275
		/* handle some special characters first. */
276
		switch (*p) {
277
		case '#':
278
			/*
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			 * skip comments.
280
			 * rustc may emit comments to dep-info.
281
			 */
282
			p++;
283
			while (*p != '\0' && *p != '\n') {
284
				/*
285
				 * escaped newlines continue the comment across
286
				 * multiple lines.
287
				 */
288
				if (*p == '\\')
289
					p++;
290
				p++;
291
			}
292
			continue;
293
		case ' ':
294
		case '\t':
295
			/* skip whitespaces */
296
			p++;
297
			continue;
298
		case '\\':
299
			/*
300
			 * backslash/newline combinations continue the
301
			 * statement. Skip it just like a whitespace.
302
			 */
303
			if (*(p + 1) == '\n') {
304
				p += 2;
305
				continue;
306
			}
307
			break;
308
		case '\n':
309
			/*
310
			 * Makefiles use a line-based syntax, where the newline
311
			 * is the end of a statement. After seeing a newline,
312
			 * we expect the next token is a target.
313
			 */
314
			p++;
315
			is_target = true;
316
			continue;
317
		case ':':
318
			/*
319
			 * assume the first dependency after a colon as the
320
			 * source file.
321
			 */
322
			p++;
323
			is_target = false;
324
			is_source = true;
325
			continue;
326
		}
327

328
		/* find the end of the token */
329
		q = p;
330
		while (*q != ' ' && *q != '\t' && *q != '\n' && *q != '#' && *q != ':') {
331
			if (*q == '\\') {
332
				/*
333
				 * backslash/newline combinations work like as
334
				 * a whitespace, so this is the end of token.
335
				 */
336
				if (*(q + 1) == '\n')
337
					break;
338

339
				/* escaped special characters */
340
				if (*(q + 1) == '#' || *(q + 1) == ':') {
341
					memmove(p + 1, p, q - p);
342
					p++;
343
				}
344

345
				q++;
346
			}
347

348
			if (*q == '\0')
349
				break;
350
			q++;
351
		}
352

353
		/* Just discard the target */
354
		if (is_target) {
355
			p = q;
356
			continue;
357
		}
358

359
		saved_c = *q;
360
		*q = '\0';
361
		need_parse = false;
362

363
		/*
364
		 * Do not list the source file as dependency, so that kbuild is
365
		 * not confused if a .c file is rewritten into .S or vice versa.
366
		 * Storing it in source_* is needed for modpost to compute
367
		 * srcversions.
368
		 */
369
		if (is_source) {
370
			/*
371
			 * The DT build rule concatenates multiple dep files.
372
			 * When processing them, only process the first source
373
			 * name, which will be the original one, and ignore any
374
			 * other source names, which will be intermediate
375
			 * temporary files.
376
			 *
377
			 * rustc emits the same dependency list for each
378
			 * emission type. It is enough to list the source name
379
			 * just once.
380
			 */
381
			if (!saw_any_target) {
382
				saw_any_target = true;
383
				printf("source_%s := %s\n\n", target, p);
384
				printf("deps_%s := \\\n", target);
385
				need_parse = true;
386
			}
387
		} else if (!is_ignored_file(p, q - p) &&
388
			   !in_hashtable(p, q - p, file_hashtab)) {
389
			printf("  %s \\\n", p);
390
			need_parse = true;
391
		}
392

393
		if (need_parse && !is_no_parse_file(p, q - p)) {
394
			void *buf;
395

396
			buf = read_file(p);
397
			parse_config_file(buf);
398
			free(buf);
399
		}
400

401
		is_source = false;
402
		*q = saved_c;
403
		p = q;
404
	}
405

406
	if (!saw_any_target) {
407
		fprintf(stderr, "fixdep: parse error; no targets found\n");
408
		exit(1);
409
	}
410

411
	printf("\n%s: $(deps_%s)\n\n", target, target);
412
	printf("$(deps_%s):\n", target);
413
}
414

415
int main(int argc, char *argv[])
416
{
417
	const char *depfile, *target, *cmdline;
418
	void *buf;
419

420
	if (argc != 4)
421
		usage();
422

423
	depfile = argv[1];
424
	target = argv[2];
425
	cmdline = argv[3];
426

427
	printf("savedcmd_%s := %s\n\n", target, cmdline);
428

429
	buf = read_file(depfile);
430
	parse_dep_file(buf, target);
431
	free(buf);
432

433
	fflush(stdout);
434

435
	/*
436
	 * In the intended usage, the stdout is redirected to .*.cmd files.
437
	 * Call ferror() to catch errors such as "No space left on device".
438
	 */
439
	if (ferror(stdout)) {
440
		fprintf(stderr, "fixdep: not all data was written to the output\n");
441
		exit(1);
442
	}
443

444
	return 0;
445
}
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