Use -std=gnu99 globally on Linux instead of per-file override for io_uring.c

Co-authored-by: ithewei <26049660+ithewei@users.noreply.github.com>

Author: Copilot

CMakeLists.txt

@@ -104,6 +104,9 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/hconfig.h.in ${CMAKE_CURRENT_SOURCE_D
 # see Makefile.in
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED True)
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    set(CMAKE_C_EXTENSIONS ON)
+endif()
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED True)
 
@@ -174,8 +177,6 @@ if(WITH_IO_URING)
         message(FATAL_ERROR "WITH_IO_URING is only supported on Linux because liburing is Linux-only.")
     endif()
     set(LIBS ${LIBS} uring)
-    # liburing headers require GNU C extensions (typeof, statement expressions, etc.)
-    set_source_files_properties(event/io_uring.c PROPERTIES COMPILE_OPTIONS "-std=gnu99")
 endif()
 
 if(WIN32 OR MINGW)

Makefile.in

@@ -87,8 +87,12 @@ endif
 endif
 
 ifeq ($(findstring -std, $(CFLAGS)), )
+ifeq ($(OS), Linux)
+override CFLAGS += -std=gnu99
+else
 override CFLAGS += -std=c99
 endif
+endif
 
 ifeq ($(findstring -std, $(CXXFLAGS)), )
 override CXXFLAGS += -std=c++11
@@ -199,13 +203,6 @@ ifeq ($(WITH_IO_URING), yes)
 endif
 endif
 
-# liburing headers require GNU C extensions (typeof, statement expressions, etc.)
-ifeq ($(OS), Linux)
-ifeq ($(WITH_IO_URING), yes)
-event/io_uring.o: event/io_uring.c
-	$(CC) $(CPPFLAGS) $(CFLAGS) -std=gnu99 -c $< -o $@
-endif
-endif
 
 LDFLAGS += $(addprefix -L, $(LIBDIRS))
 LDFLAGS += $(addprefix -l, $(LIBS))