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![Alexey Dobriyan](/assets/img/avatar_default.png)
Do you think kernel build is 100% dominated by gcc? You are wrong! One small utility called "fixdep" consistently manages to sneak into profile's first page (unless you have small monitor of course). The choke point is this clever code: for (; m < end; m++) { if (*m == INT_CONF) { p = (char *) m ; goto conf; } if (*m == INT_ONFI) { p = (char *) m-1; goto conf; } if (*m == INT_NFIG) { p = (char *) m-2; goto conf; } if (*m == INT_FIG_) { p = (char *) m-3; goto conf; } 4 branches per 4 characters is not fast. Use strstr(3), so that SSE2 etc can be used. With this patch, fixdep is so deep at the bottom, it is hard to find it. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Michal Marek <mmarek@suse.com>
449 lines
11 KiB
C
449 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 prequisites.
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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/linux/config/his/driver.h" 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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* cmd_<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.h for every
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* CONFIG_MY_OPTION encountered in any of the prequisites.
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*
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* It will also filter out all the dependencies on *.ver. We need
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* to make sure that the generated version checksum are globally up
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* to date before even starting the recursive build, so it's too late
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* at this point anyway.
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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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/*
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* Note 2: if somebody writes HELLO_CONFIG_BOOM in a file, it will depend onto
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* CONFIG_BOOM. This could seem a bug (not too hard to fix), but please do not
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* fix it! Some UserModeLinux files (look at arch/um/) call CONFIG_BOOM as
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* UML_CONFIG_BOOM, to avoid conflicts with /usr/include/linux/autoconf.h,
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* through arch/um/include/uml-config.h; this fixdep "bug" makes sure that
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* those files will have correct dependencies.
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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 <sys/mman.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 <stdlib.h>
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#include <stdio.h>
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#include <limits.h>
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#include <ctype.h>
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#include <arpa/inet.h>
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int insert_extra_deps;
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char *target;
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char *depfile;
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char *cmdline;
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static void usage(void)
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{
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fprintf(stderr, "Usage: fixdep [-e] <depfile> <target> <cmdline>\n");
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fprintf(stderr, " -e insert extra dependencies given on stdin\n");
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exit(1);
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}
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/*
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* Print out the commandline prefixed with cmd_<target filename> :=
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*/
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static void print_cmdline(void)
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{
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printf("cmd_%s := %s\n\n", target, cmdline);
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}
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/*
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* Print out a dependency path from a symbol name
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*/
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static void print_config(const char *m, int slen)
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{
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int c, i;
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printf(" $(wildcard include/config/");
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for (i = 0; i < slen; i++) {
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c = m[i];
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if (c == '_')
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c = '/';
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else
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c = tolower(c);
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putchar(c);
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}
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printf(".h) \\\n");
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}
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static void do_extra_deps(void)
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{
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if (insert_extra_deps) {
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char buf[80];
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while(fgets(buf, sizeof(buf), stdin)) {
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int len = strlen(buf);
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if (len < 2 || buf[len-1] != '\n') {
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fprintf(stderr, "fixdep: bad data on stdin\n");
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exit(1);
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}
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print_config(buf, len-1);
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}
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}
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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[0];
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};
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#define HASHSZ 256
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static struct item *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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* Lookup a value in the configuration string.
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*/
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static int is_defined_config(const char *name, int len, unsigned int hash)
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{
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struct item *aux;
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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 1;
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}
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return 0;
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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 define_config(const char *name, int len, unsigned int hash)
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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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* 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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unsigned int hash = strhash(m, slen);
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if (is_defined_config(m, slen, hash))
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return;
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define_config(m, slen, hash);
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print_config(m, slen);
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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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while ((p = strstr(p, "CONFIG_"))) {
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p += 7;
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q = p;
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while (*q && (isalnum(*q) || *q == '_'))
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q++;
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if (memcmp(q - 7, "_MODULE", 7) == 0)
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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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/* test if s ends in sub */
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static int strrcmp(const char *s, const char *sub)
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{
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int slen = strlen(s);
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int sublen = strlen(sub);
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if (sublen > slen)
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return 1;
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return memcmp(s + slen - sublen, sub, sublen);
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}
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static void do_config_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 *map;
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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 config 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 config file: ");
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perror(filename);
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exit(2);
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}
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if (st.st_size == 0) {
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close(fd);
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return;
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}
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map = malloc(st.st_size + 1);
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if (!map) {
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perror("fixdep: malloc");
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close(fd);
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return;
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}
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if (read(fd, map, st.st_size) != st.st_size) {
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perror("fixdep: read");
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close(fd);
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return;
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}
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map[st.st_size] = '\0';
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close(fd);
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parse_config_file(map);
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free(map);
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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(void *map, size_t len)
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{
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char *m = map;
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char *end = m + len;
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char *p;
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char s[PATH_MAX];
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int is_target;
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int saw_any_target = 0;
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int is_first_dep = 0;
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while (m < end) {
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/* Skip any "white space" */
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while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
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m++;
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/* Find next "white space" */
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p = m;
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while (p < end && *p != ' ' && *p != '\\' && *p != '\n')
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p++;
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/* Is the token we found a target name? */
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is_target = (*(p-1) == ':');
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/* Don't write any target names into the dependency file */
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if (is_target) {
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/* The /next/ file is the first dependency */
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is_first_dep = 1;
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} else {
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/* Save this token/filename */
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memcpy(s, m, p-m);
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s[p - m] = 0;
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/* Ignore certain dependencies */
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if (strrcmp(s, "include/generated/autoconf.h") &&
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strrcmp(s, "include/generated/autoksyms.h") &&
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strrcmp(s, "arch/um/include/uml-config.h") &&
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strrcmp(s, "include/linux/kconfig.h") &&
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strrcmp(s, ".ver")) {
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/*
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* Do not list the source file as dependency,
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* so that kbuild is not confused if a .c file
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* is rewritten into .S or vice versa. Storing
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* it in source_* is needed for modpost to
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* compute srcversions.
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*/
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if (is_first_dep) {
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/*
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* If processing the concatenation of
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* multiple dependency files, only
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* process the first target name, which
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* will be the original source name,
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* and ignore any other target names,
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* which will be intermediate temporary
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* files.
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*/
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if (!saw_any_target) {
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saw_any_target = 1;
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printf("source_%s := %s\n\n",
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target, s);
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printf("deps_%s := \\\n",
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target);
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}
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is_first_dep = 0;
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} else
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printf(" %s \\\n", s);
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do_config_file(s);
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}
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}
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/*
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* Start searching for next token immediately after the first
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* "whitespace" character that follows this token.
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*/
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m = p + 1;
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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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do_extra_deps();
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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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static void print_deps(void)
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{
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struct stat st;
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int fd;
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void *map;
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fd = open(depfile, O_RDONLY);
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if (fd < 0) {
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fprintf(stderr, "fixdep: error opening depfile: ");
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perror(depfile);
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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 depfile: ");
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perror(depfile);
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exit(2);
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}
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if (st.st_size == 0) {
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fprintf(stderr,"fixdep: %s is empty\n",depfile);
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close(fd);
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return;
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}
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map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
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if ((long) map == -1) {
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perror("fixdep: mmap");
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close(fd);
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return;
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}
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parse_dep_file(map, st.st_size);
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munmap(map, st.st_size);
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close(fd);
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}
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int main(int argc, char *argv[])
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{
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if (argc == 5 && !strcmp(argv[1], "-e")) {
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insert_extra_deps = 1;
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argv++;
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} else 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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print_cmdline();
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print_deps();
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return 0;
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}
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