From: Mike Frysinger <vapier@gentoo.org>
Date: Thu, 26 Feb 2009 08:30:06 +0000 (-0500)
Subject: make sure compiler supports warning flags
X-Git-Tag: v1.3.0~85
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=a2d010f8fca904fffa3c6e5a5d148cc96a37a08a;p=mtd-utils.git

make sure compiler supports warning flags

Some compilers (like gcc-3.3) don't support all the newer -W flags that we
are using.  So import the compiler check found in the kernel and test each
flag we add.  The := is important so we only do the compiler tests once
per `make` rather than every time we compile a file.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
---

diff --git a/common.mk b/common.mk
index 0e8c62b..5e92b07 100644
--- a/common.mk
+++ b/common.mk
@@ -1,8 +1,18 @@
 CC := $(CROSS)gcc
 AR := $(CROSS)ar
 RANLIB := $(CROSS)ranlib
+
+# Stolen from Linux build system
+try-run = $(shell set -e; ($(1)) >/dev/null 2>&1 && echo "$(2)" || echo "$(3)")
+cc-option = $(call try-run, $(CC) $(1) -c -xc /dev/null -o /dev/null,$(1),$(2))
+
 CFLAGS ?= -O2 -g
-CFLAGS += -Wall -Wextra -Wwrite-strings -Wno-sign-compare -D_FILE_OFFSET_BITS=64
+WFLAGS := -Wall \
+	$(call cc-option,-Wextra) \
+	$(call cc-option,-Wwrite-strings) \
+	$(call cc-option,-Wno-sign-compare)
+CFLAGS += $(WFLAGS)
+CPPFLAGS += -D_FILE_OFFSET_BITS=64
 
 DESTDIR ?= /usr/local
 PREFIX=/usr