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[clang] Binary literals are flagged as a GNU extension even when compiling in C23 mode #72017

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LocalSpook opened this issue Nov 11, 2023 · 1 comment · Fixed by #81658
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[clang] Binary literals are flagged as a GNU extension even when compiling in C23 mode #72017

LocalSpook opened this issue Nov 11, 2023 · 1 comment · Fixed by #81658
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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

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@LocalSpook
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C23 added binary literals into the standard, but currently, when compiling with -std=c23 -Wpedantic, the compiler emits a warning (-Wgnu-binary-literal) that they're a GNU extension.

Reproducing the error

Compile the following program with clang -std=c23 -Wpedantic:

int main() {
    return 0b0;
}

Here's that program in Compiler Explorer, compiled with Clang trunk: https://godbolt.org/z/Ezz6ox37x.

Expected behaviour

The program should compile with no warnings.

Possible solution

Don't enable -Wgnu-binary-literal as part of -Wpedantic when compiling as C23.
@github-actions github-actions bot added the clang Clang issues not falling into any other category label Nov 11, 2023
@EugeneZelenko EugeneZelenko added c23 clang:diagnostics New/improved warning or error message in Clang, but not in clang-tidy or static analyzer and removed clang Clang issues not falling into any other category labels Nov 11, 2023
@AaronBallman AaronBallman added the confirmed Verified by a second party label Feb 13, 2024
AaronBallman added a commit to AaronBallman/llvm-project that referenced this issue Feb 13, 2024
@AaronBallman
[C23] Do not diagnose binary literals as an extension
d1e840a 
We previously would diagnose them as a GNU extension in C mode, but
they are now a feature of C23. This removes the old warning group,
-Wgnu-binary-literal, as it no longer makes sense and searching through
public repositories shows it is a rarely used option (same for the -Wno
form). It also adds the companion compatibility warning which existed
for C++ but not for C.

Fixes llvm#72017
@AaronBallman AaronBallman mentioned this issue Feb 13, 2024
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AaronBallman added a commit that referenced this issue Feb 14, 2024
@AaronBallman
[C23] Do not diagnose binary literals as an extension (#81658)
8e24bc0 
We previously would diagnose them as a GNU extension in C mode, but they
are now a feature of C23. The -Wgnu-binary-literal warning group no
longer controls any diagnostics as this is no longer a GNU extension.
The warning group is retained as a noop to help avoid "unknown warning"
diagnostics.

This also adds the companion compatibility warning which existed for C++
but not for C.

Fixes #72017
@LocalSpook
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@AaronBallman Thank you!

@tbaederr tbaederr mentioned this issue Apr 19, 2024
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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
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[C23] Do not diagnose binary literals as an extension AaronBallman/llvm-project
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@AaronBallman @EugeneZelenko @LocalSpook