translate-c: incorrect handling of negative divisor in remainder operator

[ehaas]

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Zig Version

0.9.0-dev.1679+6cf8a49bb

Steps to Reproduce

Run zig translate-c on the following code:

#include <stdlib.h>
int main(void) {
   int x = 5 % -2;
   if (x != 1) abort();
}

And then zig run on the output

Expected Behavior

From the C standard: If the quotient a/b is representable, the expression (a/b)*b + a%b shall equal a. So in this case x should equal 1 and the program should exit normally.

Actual Behavior

Compile error:

./test.zig:1120:20: error: negative denominator
    var x: c_int = @rem(@as(c_int, 5), -@as(c_int, 2));

Also, if the divisor is a runtime value instead of a comptime-known one, the result is a panic at runtime.