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 2062afb4f 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. Changes in V2: - Update commit message explaining purpose. - Explicitly mention GCC version in comment. - Wrap workaround in ifdef CONFIG_CC_IS_GCC Signed-off-by: Mark Wielaard <mark@xxxxxxxxx> Acked-by: Ian Rogers <irogers@xxxxxxxxxx> Reviewed-by: Andi Kleen <andi@xxxxxxxxxxxxxx> Cc: linux-toolchains@xxxxxxxxxxxxxxx Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Cc: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> Cc: Florian Weimer <fw@xxxxxxxxxxxxx> Cc: Sedat Dilek <sedat.dilek@xxxxxxxxx> --- Makefile | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index 51540b291738..964754b4cedf 100644 --- a/Makefile +++ b/Makefile @@ -813,7 +813,11 @@ 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 ifdef CONFIG_DEBUG_INFO_SPLIT -- 2.18.4
