Shared library providing new C API functions to old stable ABI

[vstinner]

Sometimes, I wish a pythoncapi-compat-like library for the stable ABI: provide new functions on top of the existing limited C API. It would provide immediately new functions to all Python versions, maybe up to Python 3.2 stable ABI!

Currently, pythoncapi-compat is implemented as a single header files, the implementation has to be short and compatible with most C and C++ compilers. Maybe having a (new) shared library would allow to have more complicated implementations and care less about C/C++ compilers.

For example, I decided to not implement PyType_FromModuleAndSpec() in pythoncapi-compat because the implementation requires 100 to 500 lines of C code, it doesn't fit well into current pythoncapi-compat design.

Well, HPy already exists, provides a stable ABI, and works on all Python versions! :-)

[vstinner]

I created the experimental https://github.com/vstinner/deadparrot project which is a shared library. I propose to continue the experiment there, I close this issue.