[coreboot-gerrit] Change in coreboot[master]: xcompile: Disable null pointer optimizations

[Patrick Georgi (Code Review)]

Patrick Georgi has submitted this change. ( https://review.coreboot.org/c/coreboot/+/38289 )

Change subject: xcompile: Disable null pointer optimizations
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xcompile: Disable null pointer optimizations

According to the C standard, accessing the NULL pointer (memory at
address zero) is undefined behaviour, and so GCC is allowed to optimize
it out. Of course, accessing this memory location is sometimes
necessary, so this optimization can be disabled using
-fno-delete-null-pointer-checks. This is already done in coreboot, but
adding it to xcompile will also disable it for all the payloads. For
example, coreinfo compiled with LTO libpayload crashes when this flag
isn't set, presumably because the compiler is optimizing something out
that it shouldn't.

Change-Id: I4492277f02418ade3fe7a75304e8e0611f49ef36
Signed-off-by: Jacob Garber 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38289
Reviewed-by: Angel Pons 
Reviewed-by: Paul Menzel 
Tested-by: build bot (Jenkins) 
---
M Makefile.inc
M util/xcompile/xcompile
2 files changed, 1 insertion(+), 2 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Paul Menzel: Looks good to me, but someone else must approve
  Angel Pons: Looks good to me, approved

diff --git a/Makefile.inc b/Makefile.inc
index e9c5054..4ca173b 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -414,7 +414,6 @@
 CFLAGS_common += -fno-common -ffreestanding -fno-builtin -fomit-frame-pointer
 CFLAGS_common += -ffunction-sections -fdata-sections -fno-pie
 ifeq ($(CONFIG_COMPILER_GCC),y)
-CFLAGS_common += -fno-delete-null-pointer-checks
 # Don't add these GCC specific flags when running scan-build
 ifeq ($(CCC_ANALYZER_OUTPUT_FORMAT),)
 CFLAGS_common += -Wno-packed-not-aligned
diff --git a/util/xcompile/xcompile b/util/xcompile/xcompile
index 8335c34..a116407 100755
--- a/util/xcompile/xcompile
+++ b/util/xcompile/xcompile
@@ -221,7 +221,7 @@
 GCC_CC_${TARCH}:=${GCC}
 GCC_CFLAGS_${TARCH}:=${CFLAGS_GCC}
 # Generally available for GCC's cc1:
-GCC_CFLAGS_${TARCH}+=-Wlogical-op
+GCC_CFLAGS_${TARCH}+=-fno-delete-null-pointer-checks -Wlogical-op
 GCC_ADAFLAGS_${TARCH}:=${CFLAGS_GCC}
 GCC_COMPILER_RT_${TARCH}:=${CC_RT_GCC}
 GCC_COMPILER_RT_FLAGS_${TARCH}:=${CC_RT_EXTRA_GCC}