- const wchar_t *wmessage = L"out of memory";
- wchar_t *wbuf = (len < ALLOCA_LIMIT
- ? alloca (len * sizeof *wbuf)
- : len <= SIZE_MAX / sizeof *wbuf
- ? malloc (len * sizeof *wbuf)
- : NULL);
-
- if (wbuf)
- {
- size_t res;
- mbstate_t st;
- const char *tmp = message;
- memset (&st, '\0', sizeof (st));
- res = mbsrtowcs (wbuf, &tmp, len, &st);
- wmessage = res == (size_t) -1 ? L"???" : wbuf;
- }
+ wchar_t *wmessage = NULL;
+ mbstate_t st;
+ size_t res;
+ const char *tmp;
+ bool use_malloc = false;
+
+ while (1)
+ {
+ if (__libc_use_alloca (len * sizeof (wchar_t)))
+ wmessage = (wchar_t *) alloca (len * sizeof (wchar_t));
+ else
+ {
+ if (!use_malloc)
+ wmessage = NULL;
+
+ wchar_t *p = (wchar_t *) realloc (wmessage,
+ len * sizeof (wchar_t));
+ if (p == NULL)
+ {
+ free (wmessage);
+ fputws_unlocked (L"out of memory\n", stderr);
+ return;
+ }
+ wmessage = p;
+ use_malloc = true;
+ }
+
+ memset (&st, '\0', sizeof (st));
+ tmp = message;
+
+ res = mbsrtowcs (wmessage, &tmp, len, &st);
+ if (res != len)
+ break;
+
+ if (__builtin_expect (len >= SIZE_MAX / 2, 0))
+ {
+ /* This really should not happen if everything is fine. */
+ res = (size_t) -1;
+ break;
+ }
+
+ len *= 2;
+ }
+
+ if (res == (size_t) -1)
+ {
+ /* The string cannot be converted. */
+ if (use_malloc)
+ {
+ free (wmessage);
+ use_malloc = false;
+ }
+ wmessage = (wchar_t *) L"???";
+ }