[PATCH] config.mak.dev: suppress C11 extension warning for Clang on Linux

["Shardul Natu via GitGitGadget" <gitgitgadget@gmail.com>]

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.

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