2 files changed, 9 insertions, 0 deletions

diff --git a/include/fortify-headers.h b/include/fortify-headers.h
index 88a0875..3e2140f 100644
--- a/include/fortify-headers.h
+++ b/include/fortify-headers.h
@@ -99,6 +99,14 @@
 #define __diagnose_as_builtin(...)
 #endif
 
+#if __has_attribute (__diagnose_if)
+#define __warning_if(cond, msg) __attribute__ ((__diagnose_if (cond, msg, "warning")))
+#define __error_if(cond, msg) __attribute__ ((__diagnose_if (cond, msg, "error")))
+#else
+#define __warning_if(cond, msg)
+#define __error_if(cond, msg)
+#endif
+
 #endif /* __has_attribute */
 
 /*
diff --git a/include/string.h b/include/string.h
index 2c11e5e..342bde0 100644
--- a/include/string.h
+++ b/include/string.h
@@ -75,6 +75,7 @@ _FORTIFY_FN(memmove) void *memmove(void * _FORTIFY_POS0 __d,
 
 __access(write_only, 1, 3)
 __diagnose_as_builtin(__builtin_memset, 1, 2, 3)
+__warning_if(__c != 0 && __n == 0, "'memset' will set `0` bytes; did you invert the arguments?")
 _FORTIFY_FN(memset) void *memset(void * _FORTIFY_POS0 __d, int __c, size_t __n)
 {
         size_t __b = __bos(__d, 0);