From 012fb5f95d31f732810eedd06a027112abb22b93 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ren=C3=A9=20Kijewski?= <rene.kijewski@fu-berlin.de>
Date: Sat, 8 Feb 2014 18:36:38 +0100
Subject: [PATCH] Fix -fno-delete-null-pointer-checks (#664)

Only use -fno-delete-null-pointer-checks if the supplied compiler knows
the flag. Clang does not understand the flag, and does not need it.
---
 Makefile.include | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/Makefile.include b/Makefile.include
index ea237d7230..9c959133a0 100644
--- a/Makefile.include
+++ b/Makefile.include
@@ -14,7 +14,19 @@ endif
 # if you want to publish the board into the sources as an uppercase #define
 BB = $(shell echo $(BOARD)|tr 'a-z' 'A-Z')
 CPUDEF = $(shell echo $(CPU)|tr 'a-z' 'A-Z')
-CFLAGS += -DBOARD=$(BB) -DCPU_$(CPUDEF) -fno-delete-null-pointer-checks
+CFLAGS += -DBOARD=$(BB) -DCPU_$(CPUDEF)
+
+# Add `-fno-delete-null-pointer-checks` flag iff the compiler supports it.
+# GCC removes moves tests whether `x == NULL`, if previously `x` or even `x->y` was accessed.
+# 0x0 might be a sane memory location for embedded systems, so the test must not be removed.
+# Right now clang does not use the *delete-null-pointer* optimization, and does not understand the parameter.
+# Related issues: #628, #664.
+ifeq ($(shell $(CC) -fno-delete-null-pointer-checks -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
+ifeq ($(shell LANG=C $(CC) -fno-delete-null-pointer-checks -E - 2>&1 1>/dev/null </dev/null | grep warning: | grep -- -fno-delete-null-pointer-checks),)
+CFLAGS += -fno-delete-null-pointer-checks
+endif
+endif
+
 export CFLAGS
 
 export BINDIR =$(CURDIR)/bin/$(BOARD)/
-- 
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