2020-10-09 18:35:34

by Vasily Gorbik

Subject: [PATCH RESEND 1/1] perf build: Allow nested externs to enable BUILD_BUG() usage

Currently BUILD_BUG() macro is expanded to smth like the following:
do {
extern void __compiletime_assert_0(void)
__attribute__((error("BUILD_BUG failed")));
if (!(!(1)))
__compiletime_assert_0();
} while (0);

If used in a function body this obviously would produce build errors
with -Wnested-externs and -Werror.

To enable BUILD_BUG() usage in tools/arch/x86/lib/insn.c which perf
includes in intel-pt-decoder, build perf without -Wnested-externs.

Reported-by: Stephen Rothwell <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>
---
Resend with no fancy signatures.

tools/perf/Makefile.config | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 854da830b5ca..834061e94e7c 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -16,7 +16,7 @@ $(shell printf "" > $(OUTPUT).config-detected)
detected = $(shell echo "$(1)=y" >> $(OUTPUT).config-detected)
detected_var = $(shell echo "$(1)=$($(1))" >> $(OUTPUT).config-detected)

-CFLAGS := $(EXTRA_CFLAGS) $(EXTRA_WARNINGS)
+CFLAGS := $(EXTRA_CFLAGS) $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))

include $(srctree)/tools/scripts/Makefile.arch

--
2.25.4

2020-10-12 07:08:08

by Sedat Dilek

Subject: Re: [PATCH RESEND 1/1] perf build: Allow nested externs to enable BUILD_BUG() usage

On Fri, Oct 9, 2020 at 8:35 PM Vasily Gorbik <[email protected]> wrote:
>
> Currently BUILD_BUG() macro is expanded to smth like the following:

Two feedbacks:

#1: Greg KH told me to expand abbreviated words, here "smth = something".

#2: Interesting to see an ASCII-art in the signature is causing such troubles.

- Sedat -


> do {
> extern void __compiletime_assert_0(void)
> __attribute__((error("BUILD_BUG failed")));
> if (!(!(1)))
> __compiletime_assert_0();
> } while (0);
>
> If used in a function body this obviously would produce build errors
> with -Wnested-externs and -Werror.
>
> To enable BUILD_BUG() usage in tools/arch/x86/lib/insn.c which perf
> includes in intel-pt-decoder, build perf without -Wnested-externs.
>
> Reported-by: Stephen Rothwell <[email protected]>
> Signed-off-by: Vasily Gorbik <[email protected]>
> ---
> Resend with no fancy signatures.
>
> tools/perf/Makefile.config | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 854da830b5ca..834061e94e7c 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -16,7 +16,7 @@ $(shell printf "" > $(OUTPUT).config-detected)
> detected = $(shell echo "$(1)=y" >> $(OUTPUT).config-detected)
> detected_var = $(shell echo "$(1)=$($(1))" >> $(OUTPUT).config-detected)
>
> -CFLAGS := $(EXTRA_CFLAGS) $(EXTRA_WARNINGS)
> +CFLAGS := $(EXTRA_CFLAGS) $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
>
> include $(srctree)/tools/scripts/Makefile.arch
>
> --
> 2.25.4