Question

The function below basically emulates mkdir -p, recursively creating directories for a given path. With Linux I have no issues, however running under OSX it always segfaults with the error pointer being freed was not allocated during the call to free(dir). Can anyone spot an error? When I step through execution in gdb I don’t see any obvious problems, dir is populated and the directory structure is created without error.

static int
mkpath(const char *path)
{
  int result = 0;
  struct stat st;
  char *p = NULL, *dir = strdup(path);
  char *tmp = g_malloc0(sizeof(char) * strlen(cache.path) + strlen(dir) + 1);

  dir = dirname(dir);
  tmp = strcpy(tmp, cache.path);
  p = strtok(dir, "/");
  while(p != NULL) {
    tmp = strncat(tmp, "/", 1);
    tmp = strncat(tmp, p, strlen(p));

    if(stat(tmp, &st) == 0) {
      if(S_ISDIR(st.st_mode)) {
        p = strtok(NULL, "/");
        continue;
      }

      result = -ENOTDIR;
      break;
    }

    if(mkdir(tmp, S_IRWXU) == -1) {
      result = -errno;
      break;
    }

    p = strtok(NULL, "/");
  }

  free(tmp);
  free(dir);

  return result;
}

Answer 1

Take a look at the man page for dirname: http://linux.die.net/man/3/dirname. “Both dirname() and basename() return pointers to null-terminated strings. (Do not pass these pointers to free(3).)” Also, you should probably not being doing dir = dirname(dir) as you’ve then lost the pointer to the memory allocated by strdup (strdup allocated memory should be passed to free).