Add snprintf() checks

We need to use a variadic macro in this case because GCC doesn't
allow inline functions with variable argument lists.

1 files changed, 9 insertions, 3 deletions

diff --git a/include/stdio.h b/include/stdio.h
index dce15f7..237ccb0 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -13,15 +13,21 @@ int __fortify_vsnprintf(char *__restrict s, size_t n, const char *__restrict fmt
 {
         size_t bos = __builtin_object_size(s, 0);
 
-        if (bos == (size_t)-1)
-                return vsnprintf(s, n, fmt, ap);
-        if (__builtin_constant_p(n) && n > bos)
+        if (n > bos)
                 __builtin_trap();
         return vsnprintf(s, n, fmt, ap);
 }
 
 #undef vsnprintf
 #define vsnprintf(s, n, fmt, ap) __fortify_vsnprintf(s, n, fmt, ap)
+#undef snprintf
+#define snprintf(s, n, fmt, ...) ({ \
+        size_t _n = (n); \
+        size_t bos = __builtin_object_size(s, 0); \
+        if (n > bos) \
+                __builtin_trap(); \
+        snprintf(s, n, fmt, __VA_ARGS__); \
+})
 
 #endif