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Indicate that multiplication in Layout::array cannot overflow #118228

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Merged
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Nov 24, 2023
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Indicate that multiplication in Layout::array cannot overflow #118228

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6 changes: 5 additions & 1 deletion library/core/src/alloc/layout.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -450,7 +450,11 @@ impl Layout {
return Err(LayoutError);
}

let array_size = element_size * n;
// SAFETY: We just checked that we won't overflow `usize` when we multiply.
// This is a useless hint inside this function, but after inlining this helps
// deduplicate checks for whether the overall capacity is zero (e.g., in RawVec's
// allocation path) before/after this multiplication.
let array_size = unsafe { element_size.unchecked_mul(n) };

// SAFETY: We just checked above that the `array_size` will not
// exceed `isize::MAX` even when rounded up to the alignment.
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