decode fails on long stream when compiled with NONTHREADSAFE_PSEUDOSTACK

Hi - My platform (https://github.com/sle118/squeezelite-esp32) is an esp32 CPU and I've compiled opus & opusfile for that target. It works fine when using VAR_ARRAYS but this is a fair bit of stack consumption which is a scarce resource on this chipset (it mostly needs to be in internal memory - although there are ways around). The best solution is to use NONTHREADSAFE_PSEUDOSTACK and use heap. Unfortunately, what happens on most long playback is a failure after 10~30 mins.

op_read returns -136 and the issue is that there seems to be some corruption in the pseudo-stack

• op_get_packet_duration has a nsamples >> 120*48
• a general OPUS_INVALID_PACKET that can happen at many places (I've not been able to track them precisely yet)

I've compiled with O3 (same result with any O level) and for fixed point only. I've tried different values of the stack "pool", from 32 to 120k, no change.

I understand my description is too vague for allowing any analysis, but what I'm asking is that if others have seen issues when compiled with PSEUDOSTACK. I don't think there is a memory corruption somewhere else on my system as it's a very stable and runs mp3,flac,aac,alac,pcm,vorbis without issue for hours. Of course I cannot rule that out, but it only & systematically happens with opus.

Start by reproducing long playback on the ESP32 build using NONTHREADSAFE_PSEUDOSTACK, then compare it with VAR_ARRAYS. Investigate failures reported by op_read, including invalid results from op_get_packet_duration and OPUS_INVALID_PACKET; done means identifying the pseudo-stack corruption and providing a fix verified during extended playback.