BCMath BigInteger engine is affected by global scale changes

[d1823]

Hey.

It seems that the BCMath BigInteger engine gets affected by changes to scale, either through the bcscale function or global bcmath.scale. I'm not sure whether it's known, a feature, or a bug, so reporting just in case.

I haven't verified the impact of this thing, so can't say what chunk of supported operations is affected, but here's a small reproducible example based on the values that tripped our production system:

<?php

namespace Tests;

use phpseclib3\Math\BigInteger;
use PHPUnit\Framework\TestCase;

class BcScaleTest extends TestCase
{
    /**
     * @testWith [true, 0]
     *           [false, 1]
     *           [false, 2]
     *           [false, 3]
     *           [false, 12]
     *           [false, 99]
     */
    public function test(bool $expectedResult, int $scale): void
    {
        bcscale($scale);

        $this->assertEquals(
            $expectedResult,
            new BigInteger('115792089210356248762697446949407573530086143415290314195533631308867097853951', 10)->isPrime()
        );
    }
}

A quick look at the implementation of the BCMath engine shows that a bunch of calls to bc functions are missing the explicit 0 scale, but then a quick change setting it everywhere makes the test suite fail in a couple of places, so it seems the fix might be a bit more involved.

Obviously, a workaround for anybody affected is to install the GMP extension.

[terrafrost]

Does 56483a7 fix the issue for you?

[d1823]

It did. Thanks!

[terrafrost]

I'll try to do a release this weekend.

Thanks!