Avoid segfault with 'git branch' when the HEAD is detached

[git.git] / exec_cmd.c

diff --git a/exec_cmd.c b/exec_cmd.c
index 23f4873b2becf3fd992b60d06b3046b1eac8ad01..f234066defd637dc3c048ba3d9eb43f1ecbad446 100644 (file)
--- a/exec_cmd.c
+++ b/exec_cmd.c
@@ -9,12 +9,56 @@ static const char *argv0_path;
 
 const char *system_path(const char *path)
 {
+#ifdef RUNTIME_PREFIX
+       static const char *prefix;
+#else
        static const char *prefix = PREFIX;
+#endif
        struct strbuf d = STRBUF_INIT;
 
        if (is_absolute_path(path))
                return path;
 
+#ifdef RUNTIME_PREFIX
+       assert(argv0_path);
+       assert(is_absolute_path(argv0_path));
+
+       if (!prefix) {
+               const char *strip[] = {
+                       GIT_EXEC_PATH,
+                       BINDIR,
+                       0
+               };
+               const char **s;
+
+               for (s = strip; *s; s++) {
+                       const char *sargv = argv0_path + strlen(argv0_path);
+                       const char *ss = *s + strlen(*s);
+                       while (argv0_path < sargv && *s < ss
+                               && (*sargv == *ss ||
+                                   (is_dir_sep(*sargv) && is_dir_sep(*ss)))) {
+                               sargv--;
+                               ss--;
+                       }
+                       if (*s == ss) {
+                               struct strbuf d = STRBUF_INIT;
+                               /* We also skip the trailing directory separator. */
+                               assert(sargv - argv0_path - 1 >= 0);
+                               strbuf_add(&d, argv0_path, sargv - argv0_path - 1);
+                               prefix = strbuf_detach(&d, NULL);
+                               break;
+                       }
+               }
+       }
+
+       if (!prefix) {
+               prefix = PREFIX;
+               fprintf(stderr, "RUNTIME_PREFIX requested, "
+                               "but prefix computation failed.  "
+                               "Using static fallback '%s'.\n", prefix);
+       }
+#endif
+
        strbuf_addf(&d, "%s/%s", prefix, path);
        path = strbuf_detach(&d, NULL);
        return path;