From 121c5d08d53cb1f95d9881838523b0305c3f3bef Mon Sep 17 00:00:00 2001 From: Mark Wielaard Date: Sat, 17 Oct 2020 14:01:35 +0200 Subject: [PATCH] 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 Acked-by: Ian Rogers Reviewed-by: Andi Kleen Signed-off-by: Masahiro Yamada --- Makefile | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index b76c412..17a62e3 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 -- 2.7.4