[PATCH] D23135: [clang-tidy] misc-argument-comment non-strict mode

Alexander Kornienko via cfe-commits cfe-commits at lists.llvm.org
Thu Aug 4 07:45:25 PDT 2016

alexfh added inline comments.

Comment at: clang-tidy/misc/ArgumentCommentCheck.cpp:124
@@ +123,3 @@
+  InDecl = InDecl.trim('_');
+  return InComment.compare_lower(InDecl) == 0;
aaron.ballman wrote:
> alexfh wrote:
> > aaron.ballman wrote:
> > > Correct, which means this won't behave properly in some locales with UTF-8 identifiers. Consider Turkish, where İ (U+0130 “Latin Capital Letter I With Dot Above”) is the uppercase form of ı (U+0131 “Latin Small Letter Dotless I”). If the comment contains one version while the identifier contains the other, the comparison will currently fail, while a locale-aware comparison would succeed. You run into similar things with SS vs ß in German as well, where the uppercase form is two characters while the lowercase is only a single character.
> > Interesting, though it looks like there's now an official capital ẞ https://en.wikipedia.org/wiki/Capital_%E1%BA%9E (which is not frequently needed anyway, I guess).
> > 
> > At the end of the day, what we get is that the non-strict mode is currently somewhat stricter for non-ascii characters. Similar will happen with all other parts in LLVM that rely on `StringRef::compare_lower`. I don't think we need a separate test for this _here_, since it's a problem on a completely different level. And I guess the use non-ascii identifiers in C++ will cause much more serious problems than a slightly stricter clang-tidy warning ;]
> We may just have different testing philosophies -- I would advocate for a test because we know of a use case that's broken with this particular use of `compare_lower`. Not all uses of `compare_lower` are problematic, after all. However, I'm not going to fight for that test case too hard because this is hopefully an edge case that is low-impact. A FIXME would also suffice.
I'm reluctant to add a case, since the cost of making it work and maintaining on both linux and windows is higher than the value of it, IMO (it's my take out from writing clang-format's limited support for Unicode).


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