PYBIND11_PLATFORM_ABI_ID Modernization Continued (WIP)

[rwgk]

Description

WORK IN PROGRESS

PR #4953 already modernized the PYBIND11_BUILD_ABI for MSVC.

To be addressed in this PR:

• Fix MSVC MT/MD incompatibility in PYBIND11_BUILD_ABI #4953 (comment)
• Ideas from Build platform ABI tag improvements #5437
• Maybe: Fix MSVC MT/MD incompatibility in PYBIND11_BUILD_ABI #4953 (comment)
• Maybe: Also simplify the code setting the PYBIND11_INTERNALS_VERSION

Suggested changelog entry:

[rwgk]

With this PR at commit 14f8425 and logs_30720380481.zip downloaded from here:

• https://github.com/pybind/pybind11/actions/runs/11769449932/job/32780487991?pr=5439

$ cat *.txt | grep 'C.. Info: .* __pybind11_internals_v' | sed 's/.* __pybind11_internals_v[0-9]*/__pybind11_internals_vX/' | cut -d' ' -f1 | sort | uniq -c

     26 __pybind11_internals_vX_clang_libcpp_libcpp1__
     10 __pybind11_internals_vX_clang_libstdcpp_usecxx111__
     40 __pybind11_internals_vX_gcc_libstdcpp_usecxx111__
      2 __pybind11_internals_vX_icc_libstdcpp_usecxx111__
      6 __pybind11_internals_vX_mingw_libstdcpp_usecxx111__
      3 __pybind11_internals_vX_msvc_md_mscver19__
     34 __pybind11_internals_vX_msvc_md_mscver19_debug__
      3 __pybind11_internals_vX_msvc_mt_mscver1941__
      1 __pybind11_internals_vX_pgi_libstdcpp__

This doesn't look right, _LIBCPP_ABI_VERSION and _GLIBCXX_USE_CXX11_ABI always appear to be 1.

@robertmaynard I was trying to follow your #4953 (comment) but maybe I'm misunderstanding?

(I want to leave NVHPC for later.)

@wjakob @henryiii @isuruf @cryos for awareness.

[robertmaynard]

With this PR at commit 14f8425 and logs_30720380481.zip downloaded from here:

• https://github.com/pybind/pybind11/actions/runs/11769449932/job/32780487991?pr=5439

$ cat *.txt | grep 'C.. Info: .* __pybind11_internals_v' | sed 's/.* __pybind11_internals_v[0-9]*/__pybind11_internals_vX/' | cut -d' ' -f1 | sort | uniq -c

     26 __pybind11_internals_vX_clang_libcpp_libcpp1__
     10 __pybind11_internals_vX_clang_libstdcpp_usecxx111__
     40 __pybind11_internals_vX_gcc_libstdcpp_usecxx111__
      2 __pybind11_internals_vX_icc_libstdcpp_usecxx111__
      6 __pybind11_internals_vX_mingw_libstdcpp_usecxx111__
      3 __pybind11_internals_vX_msvc_md_mscver19__
     34 __pybind11_internals_vX_msvc_md_mscver19_debug__
      3 __pybind11_internals_vX_msvc_mt_mscver1941__
      1 __pybind11_internals_vX_pgi_libstdcpp__

This doesn't look right, _LIBCPP_ABI_VERSION and _GLIBCXX_USE_CXX11_ABI always appear to be 1.

@robertmaynard I was trying to follow your #4953 (comment) but maybe I'm misunderstanding?

(I want to leave NVHPC for later.)

@wjakob @henryiii @isuruf @cryos for awareness.

_GLIBCXX_USE_CXX11_ABI is a boolean which represents which ABI for a set of the C++ std containers you are using ( std::string, list? ). It is an independent axis compared to __GXX_ABI_VERSION.

__GXX_ABI_VERSION	_GLIBCXX_USE_CXX11_ABI	Notes
102	0	Only compatible with 102. Predates _GLIBCXX_USE_CXX11_ABI
1002	0	Compatible with >= 1002 && < 2000 + CXX11 abi of 0
1002	1	Compatible with >= 1002 && < 2000 + CXX11 abi of 1
1013	0	Compatible with >= 1002 && < 2000 + CXX11 abi of 0
1013	1	Compatible with >= 1002 && < 2000 + CXX11 abi of 1

This presumes that GCC will rev the major value of __GXX_ABI_VERSION when it next breaks ABI compat

[isuruf]

One more thing to fix would be to remove the compiler id _gcc or _clang as they are compatible with each other. I think the current checks are supposed to protect against the C standard library, but is too broad.