# CMAKE\_OBJC\_EXTENSIONS\_COMPUTED\_DEFAULT should be set for Clang
**URL:** https://discourse.cmake.org/t/cmake-objc-extensions-computed-default-should-be-set-for-clang/14350
**Category:** Usage
**Created:** [July 13, 2025, 10:19pm UTC](https://discourse.cmake.org/t/cmake-objc-extensions-computed-default-should-be-set-for-clang/14350 "2025-07-13T22:19:53Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@mccakit](https://discourse.cmake.org/u/mccakit)
#### Post date: [July 13, 2025, 10:19pm UTC](https://discourse.cmake.org/t/cmake-objc-extensions-computed-default-should-be-set-for-clang/14350/1 "2025-07-13T22:19:53Z")
Can anyone help?
```auto
CMake Error at C:/dev/tools/CMake/Modules/Compiler/CMakeCommonCompilerMacros.cmake:42 (message):
CMAKE_OBJC_STANDARD_COMPUTED_DEFAULT and
CMAKE_OBJC_EXTENSIONS_COMPUTED_DEFAULT should be set for Clang
(C:/dev/toolchains/llvm-project/build/bin/clang.exe) version 21.0.0
Call Stack (most recent call first):
C:/dev/tools/CMake/Modules/Compiler/Clang-OBJC.cmake:45 (__compiler_check_default_language_standard)
C:/dev/tools/CMake/Modules/CMakeOBJCInformation.cmake:25 (include)
extern/sdl3/cmake/macros.cmake:82 (enable_language)
extern/sdl3/CMakeLists.txt:68 (include)
```
toolchain
```auto
set(CMAKE_SYSTEM_NAME Darwin)
set(CMAKE_SYSTEM_PROCESSOR X86_64)
set(triple x86_64-apple-darwin)
set(CMAKE_C_COMPILER C:/dev/toolchains/llvm-project/build/bin/clang.exe)
set(CMAKE_C_COMPILER_TARGET ${triple})
set(CMAKE_CXX_COMPILER C:/dev/toolchains/llvm-project/build/bin/clang++.exe)
set(CMAKE_CXX_COMPILER_TARGET ${triple})
set(CMAKE_RC_COMPILER C:/dev/toolchains/llvm-project/build/bin/llvm-rc.exe)
set(CMAKE_LINKER_TYPE LLD)
set(CMAKE_AR C:/dev/toolchains/llvm-project/build/bin/llvm-ar.exe)
set(CMAKE_RANLIB C:/dev/toolchains/llvm-project/build/bin/llvm-ranlib.exe)
set(CMAKE_MT C:/dev/toolchains/llvm-project/build/bin/llvm-mt.exe)
set(CMAKE_ASM_COMPILER C:/dev/toolchains/llvm-project/build/bin/clang.exe)
set(CMAKE_INSTALL_NAME_TOOL C:/dev/toolchains/llvm-project/build/bin/llvm-install-name-tool.exe)
set(CMAKE_OBJC_COMPILER C:/dev/toolchains/llvm-project/build/bin/clang.exe)
set(CMAKE_OBJC_COMPILER_TARGET ${triple})
set(CMAKE_OBJCXX_COMPILER C:/dev/toolchains/llvm-project/build/bin/clang++.exe)
set(CMAKE_OBJCXX_COMPILER_TARGET ${triple})
set(CMAKE_OBJC_STANDARD_COMPUTED_DEFAULT 11)
set(CMAKE_OBJC_EXTENSIONS_COMPUTED_DEFAULT ON)
set(CMAKE_OBJCXX_STANDARD_COMPUTED_DEFAULT 17)
set(CMAKE_OBJCXX_EXTENSIONS_COMPUTED_DEFAULT ON)
set(CMAKE_OSX_SYSROOT C:/dev/sysroots/Xcode-beta/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk)
set(CMAKE_OSX_DEPLOYMENT_TARGET 14.0)
```
---
### Author:  [@ffAudio](https://discourse.cmake.org/u/ffAudio)
#### Post date: [July 18, 2025, 8:58am UTC](https://discourse.cmake.org/t/cmake-objc-extensions-computed-default-should-be-set-for-clang/14350/2 "2025-07-18T08:58:18Z")
If you didn’t intend to use OBJC on windows like myself, make sure to enable OBJC only on Apple:
```auto
if (APPLE)
enable_language(OBJC)
endif()
```
That solved it for me.
---
### Author:  [@mccakit](https://discourse.cmake.org/u/mccakit)
#### Post date: [July 18, 2025, 9:29am UTC](https://discourse.cmake.org/t/cmake-objc-extensions-computed-default-should-be-set-for-clang/14350/3 "2025-07-18T09:29:24Z")
I’m cross compiling to apple, objc is enabled by the library not me, what you are saying is only native compile, which I don’t want, I want to cross compile
---
### Author:  [@ffAudio](https://discourse.cmake.org/u/ffAudio)
#### Post date: [July 18, 2025, 9:32am UTC](https://discourse.cmake.org/t/cmake-objc-extensions-computed-default-should-be-set-for-clang/14350/4 "2025-07-18T09:32:16Z")
I see. Well, was worth a shot.
Good luck