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std.math.big.int: normalize zero result for small multiplications

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Resolves: #25221
This commit is contained in:
mlugg 2025-09-13 11:31:17 +01:00 • committed by Matthew Lugg
parent a0ec4e270e
commit 32a1aabff7
2 changed files with 10 additions and 4 deletions
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7
lib/std/math/big/int.zig
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@ -786,11 +786,10 @@ pub const Mutable = struct {
assert(rma.limbs.ptr != b.limbs.ptr); // illegal aliasing
if (a.limbs.len == 1 and b.limbs.len == 1) {
const ov = @mulWithOverflow(a.limbs[0], b.limbs[0]);
rma.limbs[0] = ov[0];
if (ov[1] == 0) {
rma.limbs[0], const overflow_bit = @mulWithOverflow(a.limbs[0], b.limbs[0]);
if (overflow_bit == 0) {
rma.len = 1;
rma.positive = (a.positive == b.positive);
rma.positive = (a.positive == b.positive) or rma.limbs[0] == 0;
return;
}
}

7
test/behavior/enum.zig
View file

@ -1325,3 +1325,10 @@ test "large enum field values" {
try expect(@intFromEnum(e) == std.math.maxInt(i128));
}
}
test "comptime @enumFromInt with signed arithmetic" {
const E = enum(i8) { foo = -1, bar = 0 };
const x: E = @enumFromInt(@as(i8, -1) * 0);
comptime assert(x == .bar);
comptime assert(@intFromEnum(x) == 0);
}