| commit | 80079c9c2f55ddfc5b1d5235d5ed6a2981fa6a97 | [log] [tgz] |
|---|---|---|
| author | Simon Tatham <simon.tatham@arm.com> | Fri Mar 14 11:57:25 2025 +0000 |
| committer | GitHub <noreply@github.com> | Fri Mar 14 11:57:25 2025 +0000 |
| tree | 492058f390611ccceacc0790a12c0b37fd7a5a47 | |
| parent | e45090e5f0bf7743fe0b00d510a903a659354ce1 [diff] |
[libc] Fix new warning in DyadicFloat::as_mantissa_type_rounded (#131148) The affected line of code converts a float's exponent from `int` to `size_t`, negating it in the process. Following clang commit 773e88f9d61399c, this provokes a warning, presumably because the conversion goes wrong if `size_t` is wider than `int` and the input value is `INT_MIN`: negating it within the `int` type is undefined behavior, with the likely (though not guaranteed) effect of leaving it still at `INT_MIN` and then sign-extending that on promotion to `size_t`. This fix adds a cast so that the promotion to `size_t` happens _before_ the negation, so that the negative input value will _always_ be sign-extended, and then the negation will make it positive again. (I don't believe this case will actually come up. `DyadicFloat` is a helper system used in processing ordinary float formats, so nothing is expected to generate an exponent with even a 16-bit absolute value, let alone 31. But it's as easy to fix it to be robust as it is to just suppress the warning!)
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