avoid some C functions that are not in C99

[mflatt]

Commit ff97b90 introduces "self-exe.c" using C99-and-later forms, which were not previously used in Chez Scheme. But it also uses strdup and strtok_r, which are widely available but not C99. Those functions turn out not to be available on some old environments that are still relevant to Racket, for example.

It always seems dumb to write yet another alternative to strdup and strtok, but the trade-off here seems worthwhile to me.

[ur4t]

How about using implementations from musl libc?

• http://git.etalabs.net/cgit/musl/tree/src/string/strdup.c
• http://git.etalabs.net/cgit/musl/tree/src/string/strtok_r.c

And it might reduce a bit of size to define those helpers only if they are not available.

[mflatt]

Ok, switched to the musl implementations. I did not try to figure out detecting when strcpy and/or strtok_r are available.

[jltaylor-us]

Why would we want to borrow code with yet another license and have to figure out what our obligations are under that license when you already had perfectly good code that does exactly what you want?

[ur4t]

Why would we want to borrow code with yet another license and have to figure out what our obligations are under that license when you already had perfectly good code that does exactly what you want?

These are our original copy_string with minor improvements and new get_self_path_generic without strtok_r (strspn and strcspn are in c99).

static char *copy_string(const char *s) {
  if (s == NULL) {
    return NULL;
  }
  size_t l = strlen(s) + 1;
  char *r = (char *)malloc(l);
  if (r == NULL) {
    return NULL;
  }
  return (char *)memcpy(r, s, l);
}

static char *get_self_path_generic(const char *exec_file) {
  if (strchr(exec_file, '/')) {
    return copy_string(exec_file);
  }
  char *pv = getenv("PATH");
  if (pv == NULL) {
    return NULL;
  }
  char *s = copy_string(pv);
  if (s == NULL) {
    return NULL;
  }
  for (char *p = s + strspn(s, ":"); *p != '\0'; p += strspn(p, ":")) {
    char *t = p;
    p += strcspn(p, ":");
    if (*p != '\0') {
      *p++ = '\0';
    }
    char *r = path_append(t, exec_file);
    if (access(r, X_OK) == 0) {
      free(s);
      return r;
    }
    free(r);
  }
  free(s);
  return NULL;
}

[mflatt]

The most recent push has the old-but-improved code.

I also looked for calls to malloc that need a check for a NULL result and added checks. I'm not sure that's really useful when allocating something the size that _NSGetExecutablePath reports, say, since it seems like a catastrophic situation. But I might be wrong, and uniformity seems like the best policy.