AaronBallman
commented
3 years ago But it's at least unexpected, in particular for C code.
I agree that this is especially strange in C, where it's already hard enough to remember that '::Foo' is supported.
The matcher seems to be correctly used in a few places within the LLVM codebase. If this is the intended behavior, then the documentation is wrong.
This has been the behavior of the matcher since it was introduced 8 years ago: https://github.com/llvm/llvm-project/commit/1dad183b38efedfb5a0248842caaa088268106c7#diff-fbafa44b28989eafe5795802cfefbad77b8cb6f6557a75ae2a8592afdb449147R794
I don't think this behavior was ever intended for C, but even for C++ it's a bit questionable given that "::foo" is a valid fully-qualified name that means "foo at the root namespace" (I would have expected the user would have to write "[A-Za-z0-9_]*::foo" in order to get the default behavior the matcher gives you). However, I'm not certain we want to invalidate 8 years' worth of user inertia behind the matcher and perhaps the most reasonable approach is to change the documentation to make these points more clear.
Manuel, what are your thoughts?
Extended Description
$ echo "void foo(void) { }" > foo.c
$ clang-query foo.c -c 'match functionDecl(matchesName("^foo"))' 0 matches.
$ clang-query foo.c -c 'match functionDecl(matchesName("^::foo"))'
Match #1:
/tmp/foo.c:1:1: note: "root" binds here void foo(void) { } ^
~~~~~ 1 match.This is clear from the code: https://github.com/llvm/llvm-project/blob/32d565b4618d31511e79dbe77aae8d456f2bf466/clang/include/clang/ASTMatchers/ASTMatchers.h#L2790
But it's at least unexpected, in particular for C code.
The matcher seems to be correctly used in a few places within the LLVM codebase. If this is the intended behavior, then the documentation is wrong.