Fix wcrtomb() check

This was breaking valid code, example:
char c;
wcrtomb(&c, L'0', st);

1 files changed, 13 insertions, 2 deletions

diff --git a/include/wchar.h b/include/wchar.h
index 0d4abfa..d87e195 100644
--- a/include/wchar.h
+++ b/include/wchar.h
@@ -17,8 +17,12 @@
 #define _FORTIFY_WCHAR_H
 
 __extension__
+#include_next <limits.h>
+__extension__
 #include_next <stdlib.h>
 __extension__
+#include_next <string.h>
+__extension__
 #include_next <wchar.h>
 
 #if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
@@ -99,10 +103,17 @@ _FORTIFY_FN(mbstowcs) size_t mbstowcs(wchar_t *__ws, const char *__s, size_t __w
 
 _FORTIFY_FN(wcrtomb) size_t wcrtomb(char *__s, wchar_t __w, mbstate_t *__st)
 {
+        char __buf[MB_LEN_MAX];
         size_t __b = __builtin_object_size(__s, 0);
+        size_t __r;
 
-        if (__s && MB_CUR_MAX > __b)
-                __builtin_trap();
+        if (__s) {
+                __r = __orig_wcrtomb(__buf, __w, __st);
+                if (__r > __b)
+                        __builtin_trap();
+                memcpy(__s, __buf, __r);
+                return __r;
+        }
         return __orig_wcrtomb(__s, __w, __st);
 }