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passing _Float16 to printf where double is expected should raise a warning #68538

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sh1boot opened this issue Oct 8, 2023 · 1 comment · Fixed by #74439
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passing _Float16 to printf where double is expected should raise a warning #68538

sh1boot opened this issue Oct 8, 2023 · 1 comment · Fixed by #74439
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clang:diagnostics New/improved warning or error message in Clang, but not in clang-tidy or static analyzer

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@sh1boot
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sh1boot commented Oct 8, 2023 •
edited

Unlike __fp16, _Float16 is passed without conversion to double, and so it's an unexpected argument type at that position when used with %f and the like, and should raise a warning.

https://godbolt.org/z/r5o7djxbd
@EugeneZelenko EugeneZelenko added clang:diagnostics New/improved warning or error message in Clang, but not in clang-tidy or static analyzer and removed new issue labels Oct 9, 2023
@sh1boot
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sh1boot commented Oct 13, 2023

Demonstration showing how GCC gives the warning and Clang does not:
https://godbolt.org/z/b6dq9Mjae

@Luhaocong Luhaocong mentioned this issue Dec 5, 2023
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Luhaocong added a commit that referenced this issue Jan 8, 2024
@Luhaocong
[Sema] Warning for _Float16 passed to format specifier '%f' (#74439)
5034994 
According to https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2844.pdf,
default argument promotions for _FloatN types has been removed.

A warning is needed to notice user to promote _Float16 to double
explicitly, and then pass it to format specifier '%f', which is
consistent with GCC.

Fixes: #68538
justinfargnoli pushed a commit to justinfargnoli/llvm-project that referenced this issue Jan 28, 2024
@Luhaocong @justinfargnoli
[Sema] Warning for _Float16 passed to format specifier '%f' (llvm#74439)
b1255e4 
According to https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2844.pdf,
default argument promotions for _FloatN types has been removed.

A warning is needed to notice user to promote _Float16 to double
explicitly, and then pass it to format specifier '%f', which is
consistent with GCC.

Fixes: llvm#68538
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[Sema] Warning for _Float16 passed to format specifier '%f' Luhaocong/llvm-project
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