[PATCH] D128745: [Sema] fix trailing parameter pack handling for function template partial ordering

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


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Comment at: clang/lib/Sema/SemaTemplateDeduction.cpp:5184
 
-  // FIXME: This mimics what GCC implements, but doesn't match up with the
-  // proposed resolution for core issue 692. This area needs to be sorted out,
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ychen wrote:
> aaron.ballman wrote:
> > aaron.ballman wrote:
> > > We tend not to use top-level const on locals in the project as a matter of style.
> > Does GCC still implement it this way?
> > 
> > One concern I have is that this will be an ABI breaking change, and I'm not certain how disruptive it will be. If GCC already made that change, it may be reasonable for us to also break it without having to add ABI tags or something special. But if these changes diverge us from GCC, that may require some extra effort to mitigate.
> Unfortunately, GCC is still using the old/non-conforming behavior. https://clang.godbolt.org/z/5K4916W71. What is the usual way to mitigate this?
You would use the `ClangABI` enumeration to alter behavior between ABI versions: https://github.com/llvm/llvm-project/blob/main/clang/include/clang/Basic/LangOptions.h#L174 like done in: https://github.com/llvm/llvm-project/blob/main/clang/lib/AST/DeclCXX.cpp#L929


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