Compiling Cpython 3.8.X with shared libffi fails

[cubanpit]

Bug report

Compiling CPython on Windows with shared libffi fails because of redefinition of some symbols (see conan-io/conan-center-index#13279).
This recent commit seems to address the problem in the next release, but it is not going to be backported.
Is it worth to open a PR to backport a fix?

I tried to compile CPython 3.8.12 and the linked PR to the Conan project shows plenty of information.

The error message with my setup is:

malloc_closure.obj : error LNK2005: ffi_closure_alloc already defined in libffi.lib(libffi.dll) [C:\Users\anonpath\source_subfolder\PCbui
ld\_ctypes.vcxproj]
malloc_closure.obj : error LNK2005: ffi_closure_free already defined in libffi.lib(libffi.dll) [C:\Users\anonpath\source_subfolder\PCbuil
d\_ctypes.vcxproj]
C:\Users\anonapath\source_subfolder\PCbuild\amd64\_ctypes.pyd : fatal error LNK1169: one or more multiply defined symbols found [C:\Users\
anonpath\source_subfolder\PCbuild\_ctypes.vcxproj]

[ronaldoussoren]

Python 3.8 is in security fix mode, and this is not a security issue. Hence this will likely not get fixed in 3.8.

The relevant issue mentions that the fix is not back ported to 3.10, which can still receive bug fixes. I don't know if this should be considered a bug or feature though and will leave that to the platform and ctypes experts.

[gpshead]

The change you'd want to backport came from #29791. I agree with Christian on the cited issue on not wanting to backport that to 3.10 (which will only receive non-security fixes for a few more weeks).