446 lines
11 KiB
C
446 lines
11 KiB
C
/*
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* "Optimize" a list of dependencies as spit out by gcc -MD
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* for the kernel build
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* ===========================================================================
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*
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* Author Kai Germaschewski
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* Copyright 2002 by Kai Germaschewski <kai.germaschewski@gmx.de>
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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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*
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* To use this list as-is however has the drawback that virtually
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* every file in the kernel includes autoconf.h.
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*
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* 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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*
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* 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
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* 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:mec@shout.net>.
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* This is a C version of syncdep.pl by Werner Almesberger.
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*
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*
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* 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.
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*
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* It first generates a line
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*
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* savedcmd_<target> = <cmdline>
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*
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* 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.
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*
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* 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.
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*
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* (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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#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>
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#include <ctype.h>
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static void usage(void)
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{
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fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
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exit(1);
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}
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struct item {
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struct item *next;
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unsigned int len;
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unsigned int hash;
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char name[];
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};
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#define HASHSZ 256
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static struct item *config_hashtab[HASHSZ], *file_hashtab[HASHSZ];
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static unsigned int strhash(const char *str, unsigned int sz)
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{
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/* fnv32 hash */
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unsigned int i, hash = 2166136261U;
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for (i = 0; i < sz; i++)
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hash = (hash ^ str[i]) * 0x01000193;
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return hash;
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}
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/*
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* Add a new value to the configuration string.
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*/
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static void add_to_hashtable(const char *name, int len, unsigned int hash,
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struct item *hashtab[])
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{
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struct item *aux = malloc(sizeof(*aux) + len);
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if (!aux) {
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perror("fixdep:malloc");
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exit(1);
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}
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memcpy(aux->name, name, len);
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aux->len = len;
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aux->hash = hash;
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aux->next = hashtab[hash % HASHSZ];
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hashtab[hash % HASHSZ] = aux;
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}
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/*
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* Lookup a string in the hash table. If found, just return true.
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* If not, add it to the hashtable and return false.
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*/
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static bool in_hashtable(const char *name, int len, struct item *hashtab[])
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{
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struct item *aux;
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unsigned int hash = strhash(name, len);
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for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
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if (aux->hash == hash && aux->len == len &&
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memcmp(aux->name, name, len) == 0)
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return true;
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}
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add_to_hashtable(name, len, hash, hashtab);
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return false;
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}
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/*
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* Record the use of a CONFIG_* word.
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*/
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static void use_config(const char *m, int slen)
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{
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if (in_hashtable(m, slen, config_hashtab))
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return;
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/* Print out a dependency path from a symbol name. */
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printf(" $(wildcard include/config/%.*s) \\\n", slen, m);
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}
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/* test if s ends in sub */
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static int str_ends_with(const char *s, int slen, const char *sub)
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{
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int sublen = strlen(sub);
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if (sublen > slen)
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return 0;
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return !memcmp(s + slen - sublen, sub, sublen);
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}
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static void parse_config_file(const char *p)
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{
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const char *q, *r;
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const char *start = p;
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while ((p = strstr(p, "CONFIG_"))) {
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if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
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p += 7;
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continue;
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}
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p += 7;
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q = p;
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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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static void *read_file(const char *filename)
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{
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struct stat st;
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int fd;
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char *buf;
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fd = open(filename, O_RDONLY);
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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);
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if (!buf) {
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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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return buf;
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}
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/* Ignore certain dependencies */
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static int is_ignored_file(const char *s, int len)
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{
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return str_ends_with(s, len, "include/generated/autoconf.h");
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}
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/* Do not parse these files */
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static int is_no_parse_file(const char *s, int len)
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{
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/* rustc may list binary files in dep-info */
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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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/*
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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)
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{
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bool saw_any_target = false;
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bool is_target = true;
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bool is_source = false;
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bool need_parse;
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char *q, saved_c;
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while (*p) {
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/* handle some special characters first. */
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switch (*p) {
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case '#':
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/*
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* skip comments.
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* rustc may emit comments to dep-info.
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*/
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p++;
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while (*p != '\0' && *p != '\n') {
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/*
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* escaped newlines continue the comment across
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* multiple lines.
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*/
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if (*p == '\\')
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p++;
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p++;
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}
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continue;
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case ' ':
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case '\t':
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/* skip whitespaces */
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p++;
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continue;
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case '\\':
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/*
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* backslash/newline combinations continue the
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* statement. Skip it just like a whitespace.
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*/
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if (*(p + 1) == '\n') {
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p += 2;
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continue;
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}
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break;
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case '\n':
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/*
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* Makefiles use a line-based syntax, where the newline
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* is the end of a statement. After seeing a newline,
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* we expect the next token is a target.
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*/
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p++;
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is_target = true;
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continue;
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case ':':
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/*
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* assume the first dependency after a colon as the
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* source file.
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*/
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p++;
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is_target = false;
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is_source = true;
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continue;
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}
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/* find the end of the token */
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q = p;
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while (*q != ' ' && *q != '\t' && *q != '\n' && *q != '#' && *q != ':') {
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if (*q == '\\') {
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/*
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* backslash/newline combinations work like as
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* a whitespace, so this is the end of token.
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*/
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if (*(q + 1) == '\n')
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break;
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/* escaped special characters */
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if (*(q + 1) == '#' || *(q + 1) == ':') {
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memmove(p + 1, p, q - p);
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p++;
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}
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q++;
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}
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if (*q == '\0')
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break;
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q++;
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}
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/* Just discard the target */
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if (is_target) {
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p = q;
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continue;
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}
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saved_c = *q;
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*q = '\0';
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need_parse = false;
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/*
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* Do not list the source file as dependency, so that kbuild is
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* not confused if a .c file is rewritten into .S or vice versa.
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* Storing it in source_* is needed for modpost to compute
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* srcversions.
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*/
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if (is_source) {
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/*
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* The DT build rule concatenates multiple dep files.
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* When processing them, only process the first source
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* name, which will be the original one, and ignore any
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* other source names, which will be intermediate
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* temporary files.
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*
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* rustc emits the same dependency list for each
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* emission type. It is enough to list the source name
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* just once.
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*/
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if (!saw_any_target) {
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saw_any_target = true;
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printf("source_%s := %s\n\n", target, p);
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printf("deps_%s := \\\n", target);
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need_parse = true;
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}
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} else if (!is_ignored_file(p, q - p) &&
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!in_hashtable(p, q - p, file_hashtab)) {
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printf(" %s \\\n", p);
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need_parse = true;
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}
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if (need_parse && !is_no_parse_file(p, q - p)) {
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void *buf;
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buf = read_file(p);
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parse_config_file(buf);
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free(buf);
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}
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is_source = false;
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*q = saved_c;
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p = q;
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}
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if (!saw_any_target) {
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fprintf(stderr, "fixdep: parse error; no targets found\n");
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exit(1);
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}
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printf("\n%s: $(deps_%s)\n\n", target, target);
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printf("$(deps_%s):\n", target);
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}
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int main(int argc, char *argv[])
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{
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const char *depfile, *target, *cmdline;
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void *buf;
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if (argc != 4)
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usage();
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depfile = argv[1];
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target = argv[2];
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cmdline = argv[3];
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printf("savedcmd_%s := %s\n\n", target, cmdline);
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buf = read_file(depfile);
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parse_dep_file(buf, target);
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free(buf);
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fflush(stdout);
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/*
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* In the intended usage, the stdout is redirected to .*.cmd files.
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* Call ferror() to catch errors such as "No space left on device".
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*/
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if (ferror(stdout)) {
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fprintf(stderr, "fixdep: not all data was written to the output\n");
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exit(1);
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}
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return 0;
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}
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