From: Pablo <pabloosabaterr@gmail.com>
Date: Thu, 07 May 2026 10:07:39 GMT
Subject: Re: [PATCH] config.mak.dev: suppress C11 extension warning for Clang on Linux
Message-ID: <CAN5EUNRn+SqALbGR3KE9zUKxUfuJrqvK+XJcq-t=biTw56m8kg@mail.gmail.com>
In-Reply-To: <pull.2291.git.git.1778120192298.gitgitgadget@gmail.com>

El jue, 7 may 2026 a las 4:16, Shardul Natu via GitGitGadget
(<gitgitgadget@gmail.com>) escribió:
>
> From: Shnatu <snatu@google.com>
>
> When building Git with Clang on Linux with DEVELOPER=1, the build fails
> because Clang treats C11 features used in glibc headers as extensions
> and raises errors due to -std=gnu99, -pedantic, and -Werror.

Hi Shnatu!
This is already being discussed at:
https://lore.kernel.org/git/20260505-b4-pks-ci-tolerate-glibc-generic-v1-1-5786386fe512@pks.im/T/#u

You might want to check out that thread.

Hope this helps,

--
Pablo

>
> Specifically, glibc's string.h uses _Generic (a C11 feature) in macros
> like strchr. When these macros are expanded in Git's C files, Clang
> warns about them being C11 extensions.
>
> GCC does not exhibit this behavior because it suppresses pedantic
> warnings for macros defined in system headers.
>
> To fix this, add -Wno-c11-extensions to DEVELOPER_CFLAGS when using
> Clang, but restrict it to Linux (uname_S == Linux). This suppresses
> the warning for glibc headers while keeping the build strict on other
> platforms (like macOS) to catch accidental C11 usage in Git's own code.
>
> Signed-off-by: Shnatu <snatu@google.com>
> ---
>     config.mak.dev: suppress C11 extension warning for Clang on Linux
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2291%2Fkiranani%2Fnext-2-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2291/kiranani/next-2-v1
> Pull-Request: https://github.com/git/git/pull/2291
>
>  config.mak.dev | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/config.mak.dev b/config.mak.dev
> index c8dcf78779..f1dcf4329a 100644
> --- a/config.mak.dev
> +++ b/config.mak.dev
> @@ -87,6 +87,9 @@ endif
>  # The bug was fixed in Apple clang 12.
>  #
>  ifneq ($(filter clang1,$(COMPILER_FEATURES)),)     # if we are using clang
> +ifeq ($(uname_S),Linux)
> +DEVELOPER_CFLAGS += -Wno-c11-extensions
> +endif
>  ifeq ($(uname_S),Darwin)                           # if we are on darwin
>  ifeq ($(filter clang12,$(COMPILER_FEATURES)),)     # if version < 12
>  DEVELOPER_CFLAGS += -Wno-missing-braces
>
> base-commit: 4f69b47b940100b02630f745a52f9d9850f122b2
> --
> gitgitgadget
>