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Re: [PATCH 5/5] Makefile: disable unaligned loads with UBSan




Am 10.07.2017 um 15:24 schrieb Jeff King:
> The undefined behavior sanitizer complains about unaligned
> loads, even if they're OK for a particular platform in
> practice. It's possible that they _are_ a problem, of
> course, but since it's a known tradeoff the UBSan errors are
> just noise.
> 
> Let's quiet it automatically by building with
> NO_UNALIGNED_LOADS when SANITIZE=undefined is in use.
> 
> Signed-off-by: Jeff King <peff@xxxxxxxx>
> ---
>   Makefile | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/Makefile b/Makefile
> index cc03b3c95..3c341b2a6 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1015,6 +1015,9 @@ endif
>   ifdef SANITIZE
>   BASIC_CFLAGS += -fsanitize=$(SANITIZE) -fno-sanitize-recover=$(SANITIZE)
>   BASIC_CFLAGS += -fno-omit-frame-pointer
> +ifeq ($(SANITIZE),undefined)
> +BASIC_CFLAGS += -DNO_UNALIGNED_LOADS
> +endif
>   endif
>   
>   ifndef sysconfdir

Nice, but let's be even nicer!

-- >8 --
Subject: [PATCH] Makefile: allow combining UBSan with other sanitizers

Multiple sanitizers can be specified as a comma-separated list.  Set
the flag NO_UNALIGNED_LOADS even if UndefinedBehaviorSanitizer is not
the only sanitizer to build with.

Signed-off-by: Rene Scharfe <l.s.r@xxxxxx>
---
 Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index ba4359ef8d..9b98535a04 100644
--- a/Makefile
+++ b/Makefile
@@ -1022,10 +1022,15 @@ ifdef DEVELOPER
 CFLAGS += $(DEVELOPER_CFLAGS)
 endif
 
+comma := ,
+empty :=
+space := $(empty) $(empty)
+
 ifdef SANITIZE
+SANITIZERS := $(foreach flag,$(subst $(comma),$(space),$(SANITIZE)),$(flag))
 BASIC_CFLAGS += -fsanitize=$(SANITIZE) -fno-sanitize-recover=$(SANITIZE)
 BASIC_CFLAGS += -fno-omit-frame-pointer
-ifeq ($(SANITIZE),undefined)
+ifneq ($(filter undefined,$(SANITIZERS)),)
 BASIC_CFLAGS += -DNO_UNALIGNED_LOADS
 endif
 endif
-- 
2.13.3