[Python-Dev] Rename Include/internals/ to Include/pycore/

[Neil Schemenauer]

On 2018-10-28, Benjamin Peterson wrote:
> I don't think more or less API should be magically included based
> on whether Py_BUILD_CORE is defined or not.

I agree.

> If we want to have private headers, we should include them where
> needed and not install them. Really, Py_BUILD_CORE should go away.
> We should be moving away from monolithic includes like Python.h to
> having each C file include exactly what it uses, private or not.

It seems that is best practice (e.g. look at Linux kernel include
file style).  I wonder however what are the real benefits to having
modular include files and directly using them as needed?

Pros for modular includes:

- speeds up build process if you have good dependency info in the
  build system.  Right now, change Python.h and everything gets
  rebuilt.  I'm not sure this is a huge advantage anymore.

- makes it clearer where an API is implemented?

Cons:

- more work to include the correct headers

- build system dependency definitions are more complicated.  Other
  systems generally have automatic dependancy generates (i.e. parse
  C files and find used includes).

A simple approach would be to introduce something like
Python-internal.h.  If you are a Python internal unit, you can
include both Python.h and Python-internal.h.  We could, over time,
split Python-iternal.h into smaller modular includes.