Overflow package reports a false negative for 0 quotient

[mvertes]

The following Go program:

package main

import "github.com/gnolang/gno/tm2/pkg/overflow"

func main() {
    var a, b int = -5, 7
    q, r, ok := overflow.Quotient(a, b)
    println(q, r, ok)
}

Gives the result 0 -5 false instead of 0 -5 true. An overflow is reported but it shouldn't be.

This affects all variants of Quotient function for signed integers: Quotient, Quotient8, Quotient16, Quotient32 and Quotient64. These functions are used for division / and remainder % operators.

The bug only affects results where the quotient is 0, all the other cases are correct. Note: in the overflow package, the test suite deliberately skipped the case where quotient is 0.

The issue is also present in https://github.com/gnolang/overflow and https://github.com/JohnCGriffin/overflow.

A fix is provided in #3250, precisely at

gno/tm2/pkg/overflow/overflow_template.sh

Line 93 in bbb84a1

status := (c < 0) == ((a < 0) != (b < 0)) || (c == 0) // no sign check for 0 quotient