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fix(buffer): prevent integer overflow in grow_if_necessary #3317

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fix(buffer): prevent integer overflow in grow_if_necessary #3317

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fix(buffer): prevent integer overflow in grow_if_necessary
bobzhang Mar 19, 2026
314ea48
docs: improve overflow guard comment in buffer grow
bobzhang Mar 20, 2026
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5 changes: 5 additions & 0 deletions buffer/buffer.mbt
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,11 @@ fn Buffer::grow_if_necessary(self : Buffer, required : Int) -> Unit {
if space >= required {
break space
}
// Guard against integer overflow: when space > Int max / 2 (1073741823),
// doubling would exceed 32-bit Int range. Fall back to exact allocation.
if space > 1073741823 {
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@peter-jerry-ye peter-jerry-ye Mar 20, 2026

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We might use a constant instead of a random number. Also the current runtime should be put into account -> moonbitlang/moonbit-docs#1155

break required
}
continue space * 2
}
if enough_space != self.data.length() {
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