From 6be2a7de19d8fe01f67207d8412fba7b468c6b11 Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@tuebingen.mpg.de>
Date: Wed, 23 Nov 2016 23:17:10 +0100
Subject: [PATCH] Compile with -Wformat-signedness if possible.

We can't activate this warning unconditionally because it is not
supported on older compilers, including clang. Therefore we introduce
a build time check and add the option only if the compiler supports it.
---
 Makefile.real | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Makefile.real b/Makefile.real
index ce4881d2..464cd68e 100644
--- a/Makefile.real
+++ b/Makefile.real
@@ -128,6 +128,13 @@ ifeq ($(uname_s),Linux)
 	LDFLAGS += -Wl,--gc-sections
 endif
 
+cc-option = $(shell \
+	$(CC) $(1) -Werror -c -x c /dev/null -o /dev/null > /dev/null 2>&1 \
+	&& echo "$(1)" \
+)
+
+STRICT_CFLAGS += $(call cc-option, -Wformat-signedness)
+
 # To put more focus on warnings, be less verbose as default
 # Use 'make V=1' to see the full commands
 ifeq ("$(origin V)", "command line")
-- 
2.39.5