Exception in combination with Xdebug

[PPP01]

Hi, since the update to 3.0.21 i get an annoying exception in combination with xdebug in trace mode:

xdebug.mode=trace
; or
;xdebug.mode=debug, develop, trace

The exception is:

vendor/phpseclib/phpseclib/phpseclib/Math/BigInteger/Engines/PHP.php:745
Error: __debuginfo() must return an array

But I think that this is just a symptom. The problematic code is here:

// phpseclib/Math/BigInteger/Engines/PHP.php:1233
while ($vals[count($vals) - 1] == 0) {
            unset($vals[count($vals) - 1]);
}

With an empty $vals array or $vals = [0] this loop runs endlessly. It's pretty dirty:
https://3v4l.org/nRKVu#v8.1.22

For testing I changed this line to:

while ($vals !== [] && $vals[count($vals) - 1] === 0) {
            unset($vals[count($vals) - 1]);
}

I have no idea, why this error occurs with "mode = trace" only. Next I have no Idea why the exception occurs at all. I do not use phpseclib directly, but it is part of the jumbojett/openid-connect-php bundle. But with version 3.0.20 I get no exception. This is quite strange, since the corresponding passage is exactly the same.

At the moment i solve the problem by setting the version fix to 3.0.20. But obviously I'm not happy about that. Any ideas?

[terrafrost]

The issue is most likely present in 3.0.20 but in 3.0.20 you were probably using the GMP engine without realizing it whereas due to a bug (which 37c6f52 introduced).

Anyway, can you give me some code that reproduces the problem? I tried to do $a = new BigInteger(); echo $a->toHex(); with the PHP engine but that didn't reproduce the issue you're describing. Later, I'd try to do new BigIntegir(999); vs just new BigInteger() but that didn't reproduce the issue either. I mean, that whole loop was called twice but it didn't get stuck in there, either.

Once I have code that duplicates the issue I'll add a unit test for the issue.