[PATCH v3] newlib: fix build with <gcc-5 versions

[Mike Frysinger]

__builtin_mul_overflow showed up with gcc-5, so stub it out for older
versions.
---
v3
- use style from Richard Earnshaw to avoid gcc-specific syntax

 newlib/libc/include/sys/cdefs.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/newlib/libc/include/sys/cdefs.h b/newlib/libc/include/sys/cdefs.h
index da729092185c..79bce1d1d78d 100644
--- a/newlib/libc/include/sys/cdefs.h
+++ b/newlib/libc/include/sys/cdefs.h
@@ -416,6 +416,10 @@
 #define	__unreachable()	((void)0)
 #endif
 
+#if !__GNUC_PREREQ__(5, 0)
+#define __builtin_mul_overflow(a, b, size) (*(size) = (a) * (b), 0)
+#endif
+
 /* XXX: should use `#if __STDC_VERSION__ < 199901'. */
 #if !__GNUC_PREREQ__(2, 7) && !defined(__INTEL_COMPILER)
 #define	__func__	NULL
-- 
2.34.1