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authorMark Wielaard <mark@klomp.org>2020-10-17 14:01:35 +0200
committerMasahiro Yamada <masahiroy@kernel.org>2020-10-21 00:28:53 +0900
commit121c5d08d53cb1f95d9881838523b0305c3f3bef (patch)
tree3e7286b299e940dac4fec5f82ac210b88e9b227d /Makefile
parent8402ee182c417a32d5e5a702f2fa2b01e76dc220 (diff)
downloadlinux-121c5d08d53cb1f95d9881838523b0305c3f3bef.tar.bz2
kbuild: Only add -fno-var-tracking-assignments for old GCC versions
Some old GCC versions between 4.5.0 and 4.9.1 might miscompile code with -fvar-tracking-assingments (which is enabled by default with -g -O2). Commit 2062afb4f804 ("Fix gcc-4.9.0 miscompilation of load_balance() in scheduler") added -fno-var-tracking-assignments unconditionally to work around this. But newer versions of GCC no longer have this bug, so only add it for versions of GCC before 5.0. This allows various tools such as a perf probe or gdb debuggers or systemtap to resolve variable locations using dwarf locations in more code. Signed-off-by: Mark Wielaard <mark@klomp.org> Acked-by: Ian Rogers <irogers@google.com> Reviewed-by: Andi Kleen <andi@firstfloor.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'Makefile')
-rw-r--r--Makefile6
1 files changed, 5 insertions, 1 deletions
diff --git a/Makefile b/Makefile
index b76c4122c967..17a62e365a38 100644
--- a/Makefile
+++ b/Makefile
@@ -814,7 +814,11 @@ KBUILD_CFLAGS += -ftrivial-auto-var-init=zero
KBUILD_CFLAGS += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
endif
-DEBUG_CFLAGS := $(call cc-option, -fno-var-tracking-assignments)
+# Workaround for GCC versions < 5.0
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61801
+ifdef CONFIG_CC_IS_GCC
+DEBUG_CFLAGS := $(call cc-ifversion, -lt, 0500, $(call cc-option, -fno-var-tracking-assignments))
+endif
ifdef CONFIG_DEBUG_INFO