Fuzzing test cases for GRegex/posix regexps

gregex.c

/*
$ gcc $(pkg-config --cflags glib-2.0) -lpthread gregex.c libglib-2.0.a libpcre.a -o gregex
$ echo -n 'pattern\ntext' | ./gregex
*/

#include <glib.h>
#include <string.h>

int main() {
    GRegex *preg;
    GMatchInfo *match_info;
    char *str;
    char *p;

    if (!g_file_get_contents("/dev/stdin", &str, NULL, NULL)) {
        return 1;
    }

    if (!(p = strchr(str, '\n')) || p == str || !p[1]) {
        return 2;
    }

    *p = 0;

    GRegexCompileFlags flags = 0; //G_REGEX_OPTIMIZE;

    if (!g_utf8_validate(str, -1, NULL)) {
        g_print("invalid utf8\n");
        flags |= G_REGEX_RAW;
    }

    if (!g_utf8_validate(p + 1, -1, NULL)) {
        g_print("invalid utf8 in text\n");
        flags |= G_REGEX_RAW;
    }

    if (!(preg = g_regex_new(str, flags, 0, NULL))) {
        return 3;
    }

    if (!g_regex_match(preg, p + 1, 0, &match_info)) {
        return 4;
    }

    while (g_match_info_matches(match_info)) {
        gchar *word = g_match_info_fetch(match_info, 0);
        g_print("Found: %s\n", word);
        g_free(word);
        g_match_info_next(match_info, NULL);
    }

    g_match_info_free(match_info);
    g_regex_unref(preg);
    g_free(str);
    return 0;
}

posix.c

/*
$ gcc $(pkg-config --cflags glib-2.0) -lpthread posix.c libglib-2.0.a -o posix
$ echo -n 'pattern\ntext' | ./posix
*/

#include <glib.h>
#include <regex.h>
#include <string.h>
#include <locale.h>

int main() {
    regex_t preg;
    char *str;
    char *p;

    setlocale(LC_ALL, "");

    if (!g_file_get_contents("/dev/stdin", &str, NULL, NULL)) {
        return 1;
    }

    if (!(p = strchr(str, '\n')) || p == str || !p[1]) {
        return 2;
    }

    *p = 0;

    int flags = REG_EXTENDED | REG_NOSUB;
    if (regcomp(&preg, str, flags) != 0) {
        return 3;
    }

    if (regexec(&preg, p + 1, 0, NULL, 0) != 0) {
        return 4;
    }

    regfree(&preg);
    g_free(str);
    return 0;
}