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Add assert for zero divisor in BigInt divMod to prevent infinite loop #11009

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Add assert for zero divisor in BigInt divMod to prevent infinite loop #11009

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21 changes: 21 additions & 0 deletions std/bigint.d
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Original file line number Diff line number Diff line change
Expand Up @@ -2293,6 +2293,7 @@ unittest
*/
void divMod(const BigInt dividend, const BigInt divisor, out BigInt quotient, out BigInt remainder) pure nothrow @safe
{
assert(!divisor.isZero(), "BigInt division by zero");
BigUint q, r;
BigUint.divMod(dividend.data, divisor.data, q, r);
quotient.sign = dividend.sign != divisor.sign;
Expand Down Expand Up @@ -2352,6 +2353,26 @@ void divMod(const BigInt dividend, const BigInt divisor, out BigInt quotient, ou
assert(remainder == 0);
}

// https://github.com/dlang/phobos/issues/10784
@system unittest
{
import core.exception : AssertError;
BigInt quotient, remainder;
bool caught;
try
divMod(BigInt("1234"), BigInt(0), quotient, remainder);
catch (AssertError)
caught = true;
assert(caught, "divMod by zero should assert");
}

// https://github.com/dlang/phobos/issues/10784
@safe pure unittest
{
import std.exception : assertThrown;
assertThrown(BigInt(100) / BigInt(0));
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@thewilsonator thewilsonator May 5, 2026

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this fails, does assertThrown only catch exceptions?

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@Herringway Herringway May 5, 2026

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It can catch any Throwable, but by default it only catches Exception.

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@dkorpel dkorpel May 6, 2026

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This is a fragile test either way, it assumes a specific checkaction for asserts. I would not write a unittest for this.

}

// https://issues.dlang.org/show_bug.cgi?id=19740
@safe unittest
{
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