[llvm-branch-commits] [clang] release/19.x: [clang][headers] Including stddef.h always redefines NULL (#99727) (PR #100191)

[Ian Anderson via llvm-branch-commits]

ian-twilightcoder wrote:

> I'm not certain whether the CI failures are related or not. I'm seeing things like:
> 
> > warning: Linking two modules of different data layouts: '/mnt/build/tools/libclc/obj.libclc.dir/cayman-r600--/generic/lib/subnormal_use_default.ll.bc' is '' whereas 'llvm-link' is 'e-p:32:32-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-S32-A5-G1'
> > warning: Linking two modules of different data layouts: '/mnt/build/tools/libclc/obj.libclc.dir/cayman-r600--/generic/lib/subnormal_helper_func.ll.bc' is '' whereas 'llvm-link' is 'e-p:32:32-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-S32-A5-G1'

Those don't _look_ related to NULL. The errors appear to be something wrong with the CMake?
```
2024-07-23T21:09:14.3963760Z CMake Error at /Users/runner/work/llvm-project/llvm-project/build/lib/cmake/llvm/AddLLVM.cmake:1029 (add_executable):
2024-07-23T21:09:14.3966280Z   add_executable cannot create target "prepare_builtins" because an imported
2024-07-23T21:09:14.3968880Z   target with the same name already exists.
```

https://github.com/llvm/llvm-project/pull/100191