In #32635, it was discovered that _cryptmodule.c was missing a dependency on crypt.h, which caused it to segfault when it was missing the proper prototype for crypt. This was fixed by adding an #include <crypt.h> to Python.h.

This include doesn't need to be in the public header; it only needs to be in _cryptmodule.c. Removing it from the public header is helpful for packagers, because it means that the libpython-dev (or whatever) package doesn't need a dependency on libcrypt-dev, only on the libcrypt runtime library.

New changeset 196998e220d6ca030e5a1c8ad63fcaed8e049a98 by Geoffrey Thomas in branch 'main':
closes bpo-44751: Move crypt.h include from public header to _cryptmodule (GH-27394)
https://github.com/python/cpython/commit/196998e220d6ca030e5a1c8ad63fcaed8e049a98

Could you backport this fix to at least 3.9 and 3.10 branches?
This is fix for regression which was previously backported to 2.7 and 3.6 branches.

New changeset 9626ac8b7421aa5fc04a30359521d24f40105141 by Miss Islington (bot) in branch '3.9':
closes bpo-44751: Move crypt.h include from public header to _cryptmodule (GH-27394)
https://github.com/python/cpython/commit/9626ac8b7421aa5fc04a30359521d24f40105141

New changeset 80285ecc8deaa2b0e7351bf4be863d1a0ad3c188 by Miss Islington (bot) in branch '3.10':
closes bpo-44751: Move crypt.h include from public header to _cryptmodule (GH-27394) (GH-28636)
https://github.com/python/cpython/commit/80285ecc8deaa2b0e7351bf4be863d1a0ad3c188

> Could you backport this fix to at least 3.9 and 3.10 branches?

Done.

> This is fix for regression which was previously backported to 2.7 and 3.6 branches.

I'm not sure what you mean.

In Python 2.7 and Python 3.6, <crypt.h> was already included by Include/Python.h:

#ifdef HAVE_CRYPT_H
#include <crypt.h>
#endif

> > This is fix for regression which was previously backported to 2.7 and 3.6 branches.
> 
> I'm not sure what you mean.
> 
> In Python 2.7 and Python 3.6, <crypt.h> was already included by Include/Python.h:

See issue #32635, where Victor Stinner backported some commit (with problematic location of '#include <crypt.h>') to 2.7 and 3.6 branches (which was released in >=2.7.15 and >=3.6).

> See issue #32635, where Victor Stinner backported some commit (with problematic location of '#include <crypt.h>') to 2.7 and 3.6 branches (which was released in >=2.7.15 and >=3.6).

crypt.h was added to Python.h by: https://github.com/python/cpython/pull/5284/files

And this change was then backported to 2.7 and 3.6. Ok, now I understand.

Well, it's now fixed in all branches accepting bugfixes.