STC VS mlib

This technique is often used to implement RAII in C. See example in Standard Template Containers. The library delivers STL-like functionality to C.

I'd say it's evil, but quite understandable very commonly used because there are no built-in alternatives in C. I basically never use void* in user-code, simply because there are no need for it when using a templating technique, like in my STC library. Even in the implementation of STC itself, void* is hardly used, if at all.

Study Other Peoples C Code and here's one that is easy to read: https://github.com/stclib/STC/releases

STC

This is more or less how C-ish templates are implemented in STC library.

As the author of a STL-like templated C container library, I had many of the exact same thoughts when implementing the unordered map. In fact, I also changed to many of the suggestions here, rather than consistently following the C++ umap API. E.g.

Sure it is. C misses a proper efficient generic standard/container library, like my https://github.com/stclib/STC, but that is irrelevant.

Smart Template Containers (STC)

Some data structure and algorithm library in C enable the (optional) separation between the interface of the container (which is expanded in your header) and its implementation (which is expanded in your source), like STC.

This uses the preprocessing library

M*LIB

Thanks to your feedback, I have added a new chapter in the documentation explaining how to do what you want. In this case, you need to inherit from the integer oplist (M_BASIC_OPLIST) and only adds the operator you need using the macro M_OPEXTEND. I have also added examples for integer and for c-string that may help you since there weren't any example with OA hashmap.

A quick bench on array(unsigned) between RXI vec and M*LIB array, which uses type generation, shows 1476 ms for RXI vec and 1116 ms for M*LIB (O2 / native / No LTO).

That was definitely part of the pain: I'm not fluent in C (professionally mainly write golang), so everything was taking me more time, and I was cursing the lack of all the niceties I'm used to. Having access to mlib that came with the firmware did help a lot, but still... Then also having to run everything through the flipper, 'screening' to it to get logs, etc. was just that extra little bit of pain.