1 files changed, 5 insertions, 2 deletions

diff --git a/include/wchar.h b/include/wchar.h
index 9e5413f..78485c0 100644
--- a/include/wchar.h
+++ b/include/wchar.h
@@ -41,10 +41,13 @@ __fortify_mbsrtowcs(wchar_t *d, const char **s,
                     size_t wn, mbstate_t *st)
 {
         size_t bos = __builtin_object_size(d, 0);
+        size_t r;
 
-        if (wn > bos / sizeof(wchar_t))
+        bos /= sizeof(wchar_t);
+        r = mbsrtowcs(d, s, wn > bos ? bos : wn, st);
+        if (bos < wn && d && *s && r != (size_t)-1)
                 __builtin_trap();
-        return mbsrtowcs(d, s, wn, st);
+        return r;
 }
 
 static inline __attribute__ ((always_inline))