std: Make abs() panic on overflow in debug mode #25441
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r? @brson (rust_highfive has picked a reviewer for you, use r? to override) |
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r? @aturon |
| @@ -569,7 +569,7 @@ macro_rules! int_impl { | |||
| #[inline] | |||
| pub fn abs(self) -> $T { | |||
| if self.is_negative() { | |||
| self.wrapping_neg() | |||
| -self | |||
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Can you leave a comment saying that this has the correct overflow semantics only if kept as inline given how std is distributed? I hope we can do something more robust in the future.
Otherwise r=me.
Debug overflow checks for arithmetic negation landed in rust-lang#24500, at which time the `abs` method on signed integers was changed to using `wrapping_neg` to ensure that the function never panicked. This implied that `abs` of `INT_MIN` would return `INT_MIN`, another negative value. When this change was back-ported to beta, however, in rust-lang#24708, the `wrapping_neg` function had not yet been backported, so the implementation was changed in rust-lang#24785 to `!self + 1`. This change had the unintended side effect of enabling debug overflow checks for the `abs` function. Consequently, the current state of affairs is that the beta branch checks for overflow in debug mode for `abs` and the nightly branch does not. This commit alters the behavior of nightly to have `abs` always check for overflow in debug mode. This change is more consistent with the way the standard library treats overflow as well, and it is also not a breaking change as it's what the beta branch currently does (albeit if by accident). cc rust-lang#25378
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Debug overflow checks for arithmetic negation landed in #24500, at which time the `abs` method on signed integers was changed to using `wrapping_neg` to ensure that the function never panicked. This implied that `abs` of `INT_MIN` would return `INT_MIN`, another negative value. When this change was back-ported to beta, however, in #24708, the `wrapping_neg` function had not yet been backported, so the implementation was changed in #24785 to `!self + 1`. This change had the unintended side effect of enabling debug overflow checks for the `abs` function. Consequently, the current state of affairs is that the beta branch checks for overflow in debug mode for `abs` and the nightly branch does not. This commit alters the behavior of nightly to have `abs` always check for overflow in debug mode. This change is more consistent with the way the standard library treats overflow as well, and it is also not a breaking change as it's what the beta branch currently does (albeit if by accident). cc #25378
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Debug overflow checks for arithmetic negation landed in #24500, at which time
the
absmethod on signed integers was changed to usingwrapping_negtoensure that the function never panicked. This implied that
absofINT_MINwould return
INT_MIN, another negative value. When this change was back-portedto beta, however, in #24708, the
wrapping_negfunction had not yet beenbackported, so the implementation was changed in #24785 to
!self + 1. Thischange had the unintended side effect of enabling debug overflow checks for the
absfunction. Consequently, the current state of affairs is that the betabranch checks for overflow in debug mode for
absand the nightly branch doesnot.
This commit alters the behavior of nightly to have
absalways check foroverflow in debug mode. This change is more consistent with the way the standard
library treats overflow as well, and it is also not a breaking change as it's
what the beta branch currently does (albeit if by accident).
cc #25378