[PATCH] D135690: [ASTMatchers] Add matcher for functions that are effectively inline

Fri Oct 14 08:32:51 PDT 2022

Trass3r added a comment.

In D135690#3858541 <https://reviews.llvm.org/D135690#3858541>, @aaron.ballman wrote:

> In D135690#3856863 <https://reviews.llvm.org/D135690#3856863>, @Trass3r wrote:
>
>> Didn't realize it has a big cost. Looking inside the `AST_MATCHER` and `REGISTER_MATCHER` macros I can't see any unique instantiations, should be memoized?
>
> IIRC, the cost may depend on the compiler. I know we had to enable `/bigobj` when building with MSVC because each template instantiation here was being added to its own section in the object file and we'd wind up with tens of thousands of sections.

Interesting, was that before/without -Zc:inline <https://learn.microsoft.com/en-us/cpp/build/reference/zc-inline-remove-unreferenced-comdat>?

> I think it might make more sense to use a local matcher if you need it only for one clang-tidy check. If we find we need it in more checks or there's a wider need for it, we can hoist it up to ASTMatchers.h so it's exposed more generally at that time. WDYT?

Yeah a quick search revealed 2 places where it might be useful:
https://github.com/llvm/llvm-project/blob/b6c6933e9548f17d567a20c83eede16b3fcb0c2b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp#L100-L101
https://github.com/llvm/llvm-project/blob/22e4203df813a8051b40adb3e2872e30fdbe1bbe/clang-tools-extra/clang-move/Move.cpp#L243-L245

Of course as shown there you can always do additional checks after matching when writing a check in C++.
But for tools like `clang-query` the matcher might be useful. Maybe there are also similar code search tools out there based on matchers?

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https://reviews.llvm.org/D135690