For package building, the scripts/package/Makefile invokes
"$(MAKE) KBUILD_SRC=", so the top Makefile is invoked recursively.
Notice NOSTDINC_FLAGS is exported and assigned with "+=", not ":=".
It means, NOSTDINC_FLAGS is accumulated in the call loop of package
build: top Makefile -> scripts/package/Makefile -> top Makefile.
Before, it was not a big deal because GCC just ignores the repeated
compile options, and $(call if_changed,...) compared the old/new
commands as a set of arguments.
However, the situation was changed by commit 9c8fa9bc08f6 ("kbuild:
fix if_change and friends to consider argument order"). Now Kbuild
compares old/new commands more precisely.
Since then, "make" followed by "make targz-pkg" always rebuilds the
whole kernel. The NOSTDINC_FLAGS is added just once for "make",
whilst twice for "make targz-pkg" as mentioned above. So, Kbuild
considers that the build command has changed despite that we want a
tarball straight away if everything is already built.
The easiest way to fix this problem is to change "+=" to ":="
for NOSTDINC_FLAGS assignment.
This effectively reverts commit e8f5bdb02ce0 ("[PATCH] Makefile
include path ordering"). Its log says that the arch Makefile may
override the include path order, but I see no arch Makefile touching
NOSTDINC_FLAGS. So, this change should have no impact unless
something outside of the kernel needs to override it.
Reported-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
---
This patch is fixing the problem reported by:
http://www.gossamer-threads.com/lists/linux/kernel/2454440
Paulo,
Thanks for your report!
Rik,
This patch is reverting your commit applied more than a decide ago.
As far as I see the kernel tree, I am not sure if it is still needed.
I am not familiar with Xen at all, so your review is very appreciated.
Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index 8d1301a..58c06be 100644
--- a/Makefile
+++ b/Makefile
@@ -767,7 +767,7 @@ KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
# arch Makefile may override CC so keep this after arch Makefile is included
-NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
+NOSTDINC_FLAGS := -nostdinc -isystem $(shell $(CC) -print-file-name=include)
CHECKFLAGS += $(NOSTDINC_FLAGS)
# warn about C99 declaration after statement
--
1.9.1
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