File 2471-sys.h-Check-for-overflow-checking-aritmethic-builtin.patch of Package erlang

From 405aca76c4bbc47352788858bf0c0749fb1f730d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 5 Mar 2019 12:28:57 +0100
Subject: [PATCH 11/15] sys.h: Check for overflow checking aritmethic builtins

Let sys.h define HAVE_OVERFLOW_CHECK_BUILTINS if the compiler supports
__builtin_mul_overflow() and the other overflow checking builtins.

The test is intentionally made in a sys.h and not as a configure test.
On Windows, beam_emu.c is always compiled using gcc, but the other
files are usually compiled with Microsoft's C compiler. With the
test in the header file, HAVE_OVERFLOW_CHECK_BUILTINS will be defined
when compiling beam_emu.c.
---
 erts/emulator/beam/sys.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/erts/emulator/beam/sys.h b/erts/emulator/beam/sys.h
index a69da4d762..a6312293cc 100644
--- a/erts/emulator/beam/sys.h
+++ b/erts/emulator/beam/sys.h
@@ -111,6 +111,23 @@
 #endif
 #endif
 
+/*
+ * Test for clang's convenient __has_builtin feature checking macro.
+ */
+#ifndef __has_builtin
+  #define __has_builtin(x) 0
+#endif
+
+/*
+ * Define HAVE_OVERFLOW_CHECK_BUILTINS if the overflow checking arithmetic
+ * builtins are available.
+ */
+#if ERTS_AT_LEAST_GCC_VSN__(5, 1, 0)
+#  define HAVE_OVERFLOW_CHECK_BUILTINS 1
+#elif __has_builtin(__builtin_mul_overflow)
+#  define HAVE_OVERFLOW_CHECK_BUILTINS 1
+#endif
+
 #include "erl_misc_utils.h"
 
 /*
-- 
2.16.4