[PATCH] makedumpfile: inhibit predefined macros when cross building

[Wang Nan]

When cross building makedumpfile, for example, build x86_64 exec for
dealing with arm vmcore, makefile passes a "-D__arm__" to gcc, but gcc
predefined macros still take effect, defines "__x86_64__". Which makes
definitions for x86_64 and arm mixed together in makedumpfile.h, causes
many problems.

This patch changes Makefile: if host arch and target arch are different,
passes "-U__$(HOST_ARCH)__" to gcc.

I have tested by running following command on x86_64 machine:

make ARCH=arm

Signed-off-by: Wang Nan <wangnan0 at huawei.com>
Cc: Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp>
Cc: kexec at lists.infradead.org
Cc: Geng Hui <hui.geng at huawei.com>
---
 Makefile | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index 2f4845c..f85cc21 100644
--- a/Makefile
+++ b/Makefile
@@ -15,10 +15,11 @@ CFLAGS_ARCH	= -g -O2 -Wall -D_FILE_OFFSET_BITS=64 \
 		    -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
 # LDFLAGS = -L/usr/local/lib -I/usr/local/include
 
+HOST_ARCH := $(shell uname -m)
 # Use TARGET as the target architecture if specified.
 # Defaults to uname -m
 ifeq ($(strip($TARGET)),)
-TARGET := $(shell uname -m)
+TARGET := $(HOST_ARCH)
 endif
 
 ARCH := $(shell echo ${TARGET}  | sed -e s/i.86/x86/ -e s/sun4u/sparc64/ \
@@ -26,8 +27,13 @@ ARCH := $(shell echo ${TARGET}  | sed -e s/i.86/x86/ -e s/sun4u/sparc64/ \
 			       -e s/s390x/s390/ -e s/parisc64/parisc/ \
 			       -e s/ppc64/powerpc64/ -e s/ppc/powerpc32/)
 
-CFLAGS += -D__$(ARCH)__
-CFLAGS_ARCH += -D__$(ARCH)__
+CROSS :=
+ifneq ($(TARGET), $(HOST_ARCH))
+CROSS := -U__$(HOST_ARCH)__
+endif
+
+CFLAGS += -D__$(ARCH)__ $(CROSS)
+CFLAGS_ARCH += -D__$(ARCH)__ $(CROSS)
 
 ifeq ($(ARCH), powerpc64)
 CFLAGS += -m64
-- 
1.8.4