Thread local storage and QNX

I am working on porting mimalloc to the QNX RTOS (7.x). After some trivial changes, I have encountered an issue related to thread local storage (TLS) on QNX, that I believe is described here: https://github.com/microsoft/mimalloc/blob/master/include/mimalloc-internal.h#L280 Basically, the TLS layer calls malloc, causing my program to fall into a recursive infinite loop.

mimalloc has workarounds for MacOSX and OpenBSD. I was wondering if you could tell me more about what is being done here, so that I might develop my own workaround for QNX.

Reading the OpenBSD workaround, it seems that mimalloc is re-purposing (hijacking) an address within the pthread struct to store a pointer to the thread-local heap. Am I reading this right? Do you do this because pthread_setspecific()/pthread_getspecific() would be too slow, or are there other reasons?

Also, can you please tell me what is insufficient with the current DragonFly "workaround?"

Start at include/mimalloc-internal.h#L280 and compare the MacOSX, OpenBSD, and DragonFly TLS workarounds, including the pthread_setspecific()/pthread_getspecific() paths mentioned in the report. Done would require establishing why these workarounds avoid recursive allocation and documenting or defining an appropriate QNX 7.x approach.

Written by the indexing model from the issue text.