source: MondoRescue/branches/2.2.5/mindi-busybox/scripts/basic/fixdep.c@ 1765

/*
 * "Optimize" a list of dependencies as spit out by gcc -MD
 * for the kernel build
 * ===========================================================================
 *
 * Author       Kai Germaschewski
 * Copyright    2002 by Kai Germaschewski  <kai.germaschewski@gmx.de>
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 *
 *
 * Introduction:
 *
 * gcc produces a very nice and correct list of dependencies which
 * tells make when to remake a file.
 *
 * To use this list as-is however has the drawback that virtually
 * every file in the kernel includes <linux/config.h> which then again
 * includes <linux/autoconf.h>
 *
 * If the user re-runs make *config, linux/autoconf.h will be
 * regenerated.  make notices that and will rebuild every file which
 * includes autoconf.h, i.e. basically all files. This is extremely
 * annoying if the user just changed CONFIG_HIS_DRIVER from n to m.
 *
 * So we play the same trick that "mkdep" played before. We replace
 * the dependency on linux/autoconf.h by a dependency on every config
 * option which is mentioned in any of the listed prequisites.
 *
 * To be exact, split-include populates a tree in include/config/,
 * e.g. include/config/his/driver.h, which contains the #define/#undef
 * for the CONFIG_HIS_DRIVER option.
 *
 * So if the user changes his CONFIG_HIS_DRIVER option, only the objects
 * which depend on "include/linux/config/his/driver.h" will be rebuilt,
 * so most likely only his driver ;-)
 *
 * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
 *
 * So to get dependencies right, there are two issues:
 * o if any of the files the compiler read changed, we need to rebuild
 * o if the command line given to the compile the file changed, we
 *   better rebuild as well.
 *
 * The former is handled by using the -MD output, the later by saving
 * the command line used to compile the old object and comparing it
 * to the one we would now use.
 *
 * Again, also this idea is pretty old and has been discussed on
 * kbuild-devel a long time ago. I don't have a sensibly working
 * internet connection right now, so I rather don't mention names
 * without double checking.
 *
 * This code here has been based partially based on mkdep.c, which
 * says the following about its history:
 *
 *   Copyright abandoned, Michael Chastain, <mailto:mec@shout.net>.
 *   This is a C version of syncdep.pl by Werner Almesberger.
 *
 *
 * It is invoked as
 *
 *   fixdep <depfile> <target> <cmdline>
 *
 * and will read the dependency file <depfile>
 *
 * The transformed dependency snipped is written to stdout.
 *
 * It first generates a line
 *
 *   cmd_<target> = <cmdline>
 *
 * and then basically copies the .<target>.d file to stdout, in the
 * process filtering out the dependency on linux/autoconf.h and adding
 * dependencies on include/config/my/option.h for every
 * CONFIG_MY_OPTION encountered in any of the prequisites.
 *
 * It will also filter out all the dependencies on *.ver. We need
 * to make sure that the generated version checksum are globally up
 * to date before even starting the recursive build, so it's too late
 * at this point anyway.
 *
 * The algorithm to grep for "CONFIG_..." is bit unusual, but should
 * be fast ;-) We don't even try to really parse the header files, but
 * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
 * be picked up as well. It's not a problem with respect to
 * correctness, since that can only give too many dependencies, thus
 * we cannot miss a rebuild. Since people tend to not mention totally
 * unrelated CONFIG_ options all over the place, it's not an
 * efficiency problem either.
 *
 * (Note: it'd be easy to port over the complete mkdep state machine,
 *  but I don't think the added complexity is worth it)
 */
/*
 * Note 2: if somebody writes HELLO_CONFIG_BOOM in a file, it will depend onto
 * CONFIG_BOOM. This could seem a bug (not too hard to fix), but please do not
 * fix it! Some UserModeLinux files (look at arch/um/) call CONFIG_BOOM as
 * UML_CONFIG_BOOM, to avoid conflicts with /usr/include/linux/autoconf.h,
 * through arch/um/include/uml-config.h; this fixdep "bug" makes sure that
 * those files will have correct dependencies.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
#include <ctype.h>
#include <arpa/inet.h>

/* bbox: not needed
#define INT_CONF ntohl(0x434f4e46)
#define INT_ONFI ntohl(0x4f4e4649)
#define INT_NFIG ntohl(0x4e464947)
#define INT_FIG_ ntohl(0x4649475f)
*/

char *target;
char *depfile;
char *cmdline;

void usage(void)

{
    fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
    exit(1);
}

/*
 * Print out the commandline prefixed with cmd_<target filename> :=
 */
void print_cmdline(void)
{
    printf("cmd_%s := %s\n\n", target, cmdline);
}

char * str_config  = NULL;
int    size_config = 0;
int    len_config  = 0;

/*
 * Grow the configuration string to a desired length.
 * Usually the first growth is plenty.
 */
void grow_config(int len)
{
    while (len_config + len > size_config) {
        if (size_config == 0)
            size_config = 2048;
        str_config = realloc(str_config, size_config *= 2);
        if (str_config == NULL)
            { perror("fixdep:malloc"); exit(1); }
    }
}



/*
 * Lookup a value in the configuration string.
 */
int is_defined_config(const char * name, int len)
{
    const char * pconfig;
    const char * plast = str_config + len_config - len;
    for ( pconfig = str_config + 1; pconfig < plast; pconfig++ ) {
        if (pconfig[ -1] == '\n'
        &&  pconfig[len] == '\n'
        &&  !memcmp(pconfig, name, len))
            return 1;
    }
    return 0;
}

/*
 * Add a new value to the configuration string.
 */
void define_config(const char * name, int len)
{
    grow_config(len + 1);

    memcpy(str_config+len_config, name, len);
    len_config += len;
    str_config[len_config++] = '\n';
}

/*
 * Clear the set of configuration strings.
 */
void clear_config(void)
{
    len_config = 0;
    define_config("", 0);
}

/*
 * Record the use of a CONFIG_* word.
 */
void use_config(char *m, int slen)
{
    char s[PATH_MAX];
    char *p;

    if (is_defined_config(m, slen))
        return;

    define_config(m, slen);

    memcpy(s, m, slen); s[slen] = 0;

    for (p = s; p < s + slen; p++) {
        if (*p == '_')
            *p = '/';
        else
            *p = tolower((int)*p);
    }
    printf("    $(wildcard include/config/%s.h) \\\n", s);
}

void parse_config_file(char *map, size_t len)
{
    /* modified for bbox */
    char *end_4 = map + len - 4; /* 4 == length of "USE_" */
    char *end_7 = map + len - 7;
    char *p = map;
    char *q;
    int off;

    for (; p < end_4; p++) {
        if (p < end_7 && p[6] == '_') {
            if (!memcmp(p, "CONFIG", 6)) goto conf7;
            if (!memcmp(p, "ENABLE", 6)) goto conf7;
        }
        /* We have at least 5 chars: for() has
         * "p < end-4", not "p <= end-4"
         * therefore we don't need to check p <= end-5 here */
        if (p[4] == '_')
            if (!memcmp(p, "SKIP", 4)) goto conf5;
        /* Ehhh, gcc is too stupid to just compare it as 32bit int */
        if (p[0] == 'U')
            if (!memcmp(p, "USE_", 4)) goto conf4;
        continue;

    conf4:  off = 4;
    conf5:  off = 5;
    conf7:  off = 7;
        p += off;
        for (q = p; q < end_4+4; q++) {
            if (!(isalnum(*q) || *q == '_'))
                break;
        }
        use_config(p, q-p);
    }
}

/* test is s ends in sub */
int strrcmp(char *s, char *sub)
{
    int slen = strlen(s);
    int sublen = strlen(sub);

    if (sublen > slen)
        return 1;

    return memcmp(s + slen - sublen, sub, sublen);
}

void do_config_file(char *filename)
{
    struct stat st;
    int fd;
    void *map;

    fd = open(filename, O_RDONLY);
    if (fd < 0) {
        fprintf(stderr, "fixdep: ");
        perror(filename);
        exit(2);
    }
    fstat(fd, &st);
    if (st.st_size == 0) {
        close(fd);
        return;
    }
    map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    if ((long) map == -1) {
        perror("fixdep: mmap");
        close(fd);
        return;
    }

    parse_config_file(map, st.st_size);

    munmap(map, st.st_size);

    close(fd);
}

void parse_dep_file(void *map, size_t len)
{
    char *m = map;
    char *end = m + len;
    char *p;
    char s[PATH_MAX];

    p = memchr(m, ':', len);
    if (!p) {
        fprintf(stderr, "fixdep: parse error\n");
        exit(1);
    }
    memcpy(s, m, p-m); s[p-m] = 0;
    printf("deps_%s := \\\n", target);
    m = p+1;

    clear_config();

    while (m < end) {
        while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
            m++;
        p = m;
        while (p < end && *p != ' ') p++;
        if (p == end) {
            do p--; while (!isalnum(*p));
            p++;
        }
        memcpy(s, m, p-m); s[p-m] = 0;
        if (strrcmp(s, "include/autoconf.h") &&
            strrcmp(s, "arch/um/include/uml-config.h") &&
            strrcmp(s, ".ver")) {
            printf("  %s \\\n", s);
            do_config_file(s);
        }
        m = p + 1;
    }
    printf("\n%s: $(deps_%s)\n\n", target, target);
    printf("$(deps_%s):\n", target);
}

void print_deps(void)
{
    struct stat st;
    int fd;
    void *map;

    fd = open(depfile, O_RDONLY);
    if (fd < 0) {
        fprintf(stderr, "fixdep: ");
        perror(depfile);
        exit(2);
    }
    fstat(fd, &st);
    if (st.st_size == 0) {
        fprintf(stderr,"fixdep: %s is empty\n",depfile);
        close(fd);
        return;
    }
    map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    if ((long) map == -1) {
        perror("fixdep: mmap");
        close(fd);
        return;
    }

    parse_dep_file(map, st.st_size);

    munmap(map, st.st_size);

    close(fd);
}

void traps(void)
{
/* bbox: not needed
    static char test[] __attribute__((aligned(sizeof(int)))) = "CONF";

    if (*(int *)test != INT_CONF) {
        fprintf(stderr, "fixdep: sizeof(int) != 4 or wrong endianess? %#x\n",
            *(int *)test);
        exit(2);
    }
*/
}

int main(int argc, char **argv)
{
    traps();

    if (argc != 4)
        usage();

    depfile = argv[1];
    target = argv[2];
    cmdline = argv[3];

    print_cmdline();
    print_deps();

    return 0;
}