linux-kernel - Re: [PATCH v3 14/14] selftests/nolibc: enable compiler warnings

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Date:   Sat, 5 Aug 2023 18:23:27 +0200
From:   Willy Tarreau <w@....eu>
To:     Thomas Weißschuh <linux@...ssschuh.net>
Cc:     Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yuan Tan <tanyuan@...ylab.org>,
        Zhangjin Wu <falcon@...ylab.org>
Subject: Re: [PATCH v3 14/14] selftests/nolibc: enable compiler warnings

On Thu, Aug 03, 2023 at 09:28:58AM +0200, Thomas Weißschuh wrote:
> It will help the developers to avoid cruft and detect some bugs.
> 
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
>  tools/testing/selftests/nolibc/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
> index b82d29b6c37f..e8d09cbee2ab 100644
> --- a/tools/testing/selftests/nolibc/Makefile
> +++ b/tools/testing/selftests/nolibc/Makefile
> @@ -79,7 +79,7 @@ endif
>  CFLAGS_s390 = -m64
>  CFLAGS_mips = -EL
>  CFLAGS_STACKPROTECTOR ?= $(call cc-option,-mstack-protector-guard=global $(call cc-option,-fstack-protector-all))
> -CFLAGS  ?= -Os -fno-ident -fno-asynchronous-unwind-tables -std=c89 \
> +CFLAGS  ?= -Os -fno-ident -fno-asynchronous-unwind-tables -std=c89 -W -Wall -Wextra \
>  		$(call cc-option,-fno-stack-protector) \
>  		$(CFLAGS_$(ARCH)) $(CFLAGS_STACKPROTECTOR)
>  LDFLAGS :=

I'm now getting this with gcc < 9:

  nolibc-test.c: In function 'test_pipe':
  nolibc-test.c:811:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (len != strlen(msg))
            ^
The reason is that len is ssize_t and strlen() is size_t. I tried different
approaches here but the cleanest remains turning len to size_t (we don't
use its sign anyway), so I'll do that one as well.

Cheers,
Willy