File compile_c_only_libs_with_c11_std.patch of Package widelands

From d0c9f68514ee2a71d8924010ec092813aad6d069 Mon Sep 17 00:00:00 2001
From: Benedikt Straub <benedikt-straub@web.de>
Date: Tue, 15 Apr 2025 13:28:28 +0200
Subject: [PATCH] Compile C-only libraries with c11 standard

---
 CMakeLists.txt          | 3 +++
 cmake/WlFunctions.cmake | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 241b85241ca..7e7f7907794 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -276,6 +276,7 @@ if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
   endif()
 elseif(MSVC)
   wl_add_flag(WL_GENERIC_CXX_FLAGS "/std:c++17")
+  wl_add_flag(WL_GENERIC_C_LIBRARY_FLAGS "/std:c11")
   # https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/
   # Disabled warnings that are overly verbose right now or just do not make sense.
   wl_add_flag(WL_COMPILE_DIAGNOSTICS "/wd4244")
@@ -288,6 +289,7 @@ else()
   if(WIN32)
     # This is needed for getenv().
     wl_add_flag(WL_GENERIC_CXX_FLAGS "-std=gnu++17")
+    wl_add_flag(WL_GENERIC_C_LIBRARY_FLAGS "-std=c11")
     if (OPTION_BUILD_WINSTATIC)
       set(CMAKE_CXX_STANDARD_LIBRARIES "-static-libgcc -static-libstdc++ ${CMAKE_CXX_STANDARD_LIBRARIES}")
       set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,-Bstatic")
@@ -369,6 +371,7 @@ if(NOT MSVC)
   endif()
 
   wl_add_flag(WL_GENERIC_CXX_FLAGS "-std=c++17")
+  wl_add_flag(WL_GENERIC_C_LIBRARY_FLAGS "-std=c11")
 endif()
 
 # Cross-compile-unit optimization slows linking significantly.
diff --git a/cmake/WlFunctions.cmake b/cmake/WlFunctions.cmake
index 9a84ba06823..112ce93ef52 100644
--- a/cmake/WlFunctions.cmake
+++ b/cmake/WlFunctions.cmake
@@ -65,6 +65,9 @@ macro(_common_compile_tasks)
     # This is needed for header only libraries. While they do not really mean
     # anything for cmake, they are useful to make dependencies explicit.
     set_target_properties(${NAME} PROPERTIES LINKER_LANGUAGE CXX)
+  else()
+    set(TARGET_COMPILE_FLAGS "${TARGET_COMPILE_FLAGS} ${WL_GENERIC_C_LIBRARY_FLAGS}")
+    set_target_properties(${NAME} PROPERTIES LINKER_LANGUAGE C)
   endif()
 
   set(TARGET_COMPILE_FLAGS "${TARGET_COMPILE_FLAGS} ${WL_OPTIMIZE_FLAGS} ${WL_DEBUG_FLAGS}")