[PATCH] D91531: [RFC][OpenCL] Provide mechanisms for defining extension macros

[Anton Zabaznov via Phabricator via cfe-commits]

azabaznov added a comment.

> Perhaps if you give me an example it would help to understand

I was meant that this can potentially be used to undefine macros inside clang directly. In this case there will no need to add a lot of conditional preprocessor directives in the header, also the existing interface (`-cl-ext=-cl_khr_depth_images`) will be preserved. So for example in the header there was specified an extension definition. Can undef directive be allocated and bound to a specific source location right after extension definition if `-cl-ext=-cl_khr_depth_images` was specifed:

  #if defined(__OPENCL_CPP_VERSION__) || (__OPENCL_C_VERSION__ == CL_VERSION_2_0) || \
      (__OPENCL_C_VERSION__ >= CL_VERSION_1_2  && defined(__SPIR__) )
  #define cl_khr_depth_images 1
  #endif
  
  // Bind undef directive here

I understand that this sounds tricky, but preserving interface sound reasonable for me.


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https://reviews.llvm.org/D91531