[Python-Dev] Python initialization and embedded Python

[Steve Dower]

On 17Nov2017 1601, Victor Stinner wrote:
> In short, it means that using the "Python runtime" before it's
> initialized by _PyRuntime_Initialize() is now likely to crash. For
> example, calling PyMem_RawMalloc(), before calling
> _PyRuntime_Initialize(), now calls the function NULL: dereference a
> NULL pointer, and so immediately crash with a segmentation fault.
> 
> I'm writing this email to ask if this change is an issue or not to
> embedded Python and the Python C API. Is it still possible to call
> "all" functions of the C API before calling Py_Initialize()?

I thought it was never possible to call most of the C API without 
initializing, except for certain APIs that are documented as being safe. 
I've certainly crashed many times calling C APIs before initialization. 
My intuition was that the only safe ones before were those that were 
used to initialize the runtime (Py_SetPath and such), which are also the 
ones being "upgraded" as part of this work.

If we have a good idea of which ones are [un]safe now, perhaps we should 
tag them explicitly in the docs? Do we know which ones are [un]safe?

Cheers,
Steve