From 5631d9c429857194bd55d7bcd8fa5bdd1a9899a3 Mon Sep 17 00:00:00 2001
From: Michal Marek <mmarek@suse.com>
Date: Wed, 19 Aug 2015 17:36:41 +0200
Subject: [PATCH] kbuild: Fix clang detection

We cannot detect clang before including the arch Makefile, because that
can set the default cross compiler. We also cannot detect clang after
including the arch Makefile, because powerpc wants to know about clang.
Solve this by using an deferred variable. This costs us a few shell
invocations, but this is only a constant number.

Reported-by: Behan Webster <behanw@converseincode.com>
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
---
 Makefile                   | 9 +--------
 arch/powerpc/Makefile      | 8 ++++----
 scripts/Kbuild.include     | 4 ++++
 scripts/Makefile.extrawarn | 2 +-
 4 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/Makefile b/Makefile
index 13270c0a93363f..5ccbb58553aba7 100644
--- a/Makefile
+++ b/Makefile
@@ -661,14 +661,7 @@ endif
 endif
 KBUILD_CFLAGS += $(stackp-flag)
 
-ifeq ($(shell $(CC) -v 2>&1 | grep -c "clang version"), 1)
-COMPILER := clang
-else
-COMPILER := gcc
-endif
-export COMPILER
-
-ifeq ($(COMPILER),clang)
+ifeq ($(cc-name),clang)
 KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
 KBUILD_CPPFLAGS += $(call cc-option,-Wno-unknown-warning-option,)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable)
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 05f464eb69527e..dfe88896b06c09 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -67,7 +67,7 @@ UTS_MACHINE := $(OLDARCH)
 
 ifeq ($(CONFIG_CPU_LITTLE_ENDIAN),y)
 override CC	+= -mlittle-endian
-ifneq ($(COMPILER),clang)
+ifneq ($(cc-name),clang)
 override CC	+= -mno-strict-align
 endif
 override AS	+= -mlittle-endian
@@ -333,7 +333,7 @@ TOUT	:= .tmp_gas_check
 # - Require gcc 4.0 or above on 64-bit
 # - gcc-4.2.0 has issues compiling modules on 64-bit
 checkbin:
-	@if test "${COMPILER}" != "clang" \
+	@if test "$(cc-name)" != "clang" \
 	    && test "$(cc-version)" = "0304" ; then \
 		if ! /bin/echo mftb 5 | $(AS) -v -mppc -many -o $(TOUT) >/dev/null 2>&1 ; then \
 			echo -n '*** ${VERSION}.${PATCHLEVEL} kernels no longer build '; \
@@ -342,14 +342,14 @@ checkbin:
 			false; \
 		fi ; \
 	fi
-	@if test "${COMPILER}" != "clang" \
+	@if test "$(cc-name)" != "clang" \
 	    && test "$(cc-version)" -lt "0400" \
 	    && test "x${CONFIG_PPC64}" = "xy" ; then \
                 echo -n "Sorry, GCC v4.0 or above is required to build " ; \
                 echo "the 64-bit powerpc kernel." ; \
                 false ; \
         fi
-	@if test "${COMPILER}" != "clang" \
+	@if test "$(cc-name)" != "clang" \
 	    && test "$(cc-fullversion)" = "040200" \
 	    && test "x${CONFIG_MODULES}${CONFIG_PPC64}" = "xyy" ; then \
 		echo -n '*** GCC-4.2.0 cannot compile the 64-bit powerpc ' ; \
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index d3437b82ac256c..3523df61339105 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -128,6 +128,10 @@ cc-option-align = $(subst -functions=0,,\
 cc-disable-warning = $(call try-run,\
 	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
 
+# cc-name
+# Expands to either gcc or clang
+cc-name = $(shell $(CC) -v 2>&1 | grep -q "clang version" && echo clang || echo gcc)
+
 # cc-version
 cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh $(CC))
 
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index f734033af219d2..4efedcbe4165f4 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -56,7 +56,7 @@ endif
 KBUILD_CFLAGS += $(warning)
 else
 
-ifeq ($(COMPILER),clang)
+ifeq ($(cc-name),clang)
 KBUILD_CFLAGS += $(call cc-disable-warning, initializer-overrides)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-value)
 KBUILD_CFLAGS += $(call cc-disable-warning, format)