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Unknown type attributes are diagnosed twice with [[]] spelling #54817

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AaronBallman opened this issue Apr 8, 2022 · 6 comments
Closed

Unknown type attributes are diagnosed twice with [[]] spelling #54817

AaronBallman opened this issue Apr 8, 2022 · 6 comments
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c++11 c23 clang:diagnostics New/improved warning or error message in Clang, but not in clang-tidy or static analyzer confirmed Verified by a second party good first issue https://github.com/llvm/llvm-project/contribute

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@AaronBallman
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Consider:

void func(void) {
  int [[attr]] i;
  (void)sizeof(int [[attr]]);
}

This generates four diagnostics, two for each unknown attribute. See https://godbolt.org/z/r6eGx1W6E for an example. The same does not happen for declaration attributes or statement attributes, and it does not happen for unknown type attributes spelled with __attribute__.
@AaronBallman AaronBallman added good first issue https://github.com/llvm/llvm-project/contribute c++11 c23 clang:diagnostics New/improved warning or error message in Clang, but not in clang-tidy or static analyzer confirmed Verified by a second party labels Apr 8, 2022
@llvmbot
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llvmbot commented Apr 8, 2022

@llvm/issue-subscribers-good-first-issue

@llvmbot
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llvmbot commented Apr 8, 2022

@llvm/issue-subscribers-c-11

@llvmbot
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llvmbot commented Apr 8, 2022

@llvm/issue-subscribers-c2x

@ps-19
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ps-19 commented Apr 8, 2022

Sir can you please give little hint on how can one resolve this issue?

@AaronBallman
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The way I'd approach this is to look at all the places where warn_unknown_attribute_ignored shows up in diagnostic code. I'd see what code paths are taken that lead to diagnosing it twice, and then see if there's a way to ensure that doesn't happen (without breaking any existing tests).

@junaire
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junaire commented Apr 9, 2022

A potential fix: https://reviews.llvm.org/D123447

mem-frob pushed a commit to draperlaboratory/hope-llvm-project that referenced this issue Oct 7, 2022
@junaire
[Clang] Fix unknown type attributes diagnosed twice with [[]] spelling
ba2d7ba 
Don't warn on unknown type attributes in Parser::ProhibitCXX11Attributes
for most cases, but left the diagnostic to the later checks.
module declaration and module import declaration are special cases.

Fixes llvm/llvm-project#54817

Differential Revision: https://reviews.llvm.org/D123447
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c++11 c23 clang:diagnostics New/improved warning or error message in Clang, but not in clang-tidy or static analyzer confirmed Verified by a second party good first issue https://github.com/llvm/llvm-project/contribute
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@AaronBallman @llvmbot @ps-19 @junaire