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

[Marco Antognini via Phabricator via cfe-commits]

mantognini added a comment.

When reading the documentation [1] for -cl-ext (which I've never used so far), I've noticed nothing is said about non-standard configurations (such as disabling cl_khr_depth_images with CL2.0). Quickly testing this shows that options can be specified to produce non-standard behaviour, as shown by https://godbolt.org/z/1Yz1Md.

Is it intentional that -cl-ext allows such non-standard behaviour? (This question is not necessarily address to @Anastasia.)
/If so/, then these statements

> Defining __undef_cl_khr_depth_images can alter the default behavior of the predefined macro. This is equivalent to passing -cl-ext=-cl_khr_depth_images.

and

> cl_khr_depth_images is a core functionality of CL2.0 and thefore defining __undef_cl_khr_depth_images doesn't modify the default behavior.

are slightly contradicting each other: the approach with __undef macros seems to ensure a more conformant behaviour.

I'm mainly asking for clarification in order to know in which direction we want to go, as one could also argue the present documentation doesn't imply non-standard behaviour is desired and that the current implementation of -cl-ext is buggy.

[1] https://clang.llvm.org/docs/UsersManual.html#cmdoption-cl-ext


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