Memory leaks in 15.0 / 15.1 vs 14.0

[brendanheywood]

We have run into an issue in the context of Moodle which uses redis for caching and as part of that can optionally compress and decompress values before insertion into redis using zstd.

https://github.com/moodle/moodle/blob/main/public/cache/stores/redis/lib.php#L1086-L1087

In the last couple weeks we started getting wide ranging memory blow outs and we've traced it back to version 15.0+ consuming way more memory than 14.0. It's not clear to me if this is an issue in php-ext-zstd or in zstd itself but logging it here as a starting point. I can't see anything yet related in https://github.com/facebook/zstd/issues

[kjdev]

I ran tests using run-tests.php's Test for memory leaks and compression/decompression cycles.
No memory leaks were found.

[kjdev]

Mr. chschneider has made the corrections.

The revised version 0.15.2 has been released.
Please review it.

[brendanheywood]

thanks @kjdev and @chschneider for the fast response and fix, we have tested this and its confirmed solved :)