[ryanmrichard]

Diagnostic only — please do not merge. Opened to answer one question; will be closed once CI reports.

What this measures

test_cmake_build fails on all four legs because extra_pip_packages: nwchemex installs the published wheels before configure, so nwx_ecosystem_dependency takes its installed-wheel branch and the C++ build links prebuilt binaries produced by a different toolchain than the dev matrix uses. Verified by reading the published wheels' symbol tables:

leg	wheel's C++ runtime	runner's	result
ubuntu-latest gcc-14 / clang-18	libstdc++, old COW std::string ABI	libstdc++, new ABI	link fails
macos-14 gcc-14	libc++	libstdc++	link/load fails
macos-14 clang-18	libc++	libc++	links, then all 4 tests segfault

The third row is unattributed. Setting NWX_ECOSYSTEM_FROM_SOURCE=ON skips the installed-wheel branch, so every leg compiles the ecosystem from git master with a single compiler and the ABI variable disappears.

• Still segfaults → it is the pre-existing SCF#70 pybind11 issue.
• Goes green → the segfault was itself an ABI artifact (likely Homebrew LLVM's libc++ vs. the SDK libc++ the wheels were built against), which would mean the standard library is not a single axis and planned per-stdlib wheel variants would not be sufficient.

Either way this run also measures whether from-source resolution is a viable interim unblock for #75.

Related

The Linux half is being fixed separately by moving the wheel build to manylinux_2_28 — manylinux2014's devtoolset-10 is built with _GLIBCXX_USE_DUAL_ABI 0 and its c++config.h discards any -D_GLIBCXX_USE_CXX11_ABI=1, so the new ABI is compiled out of that toolchain entirely.

🤖 Generated with Claude Code

[ryanmrichard]

Diagnostic complete — closing without merging.

Result: macos-14/clang-18 passed, so its segfault was an ABI artifact (AppleClang-built libc++ wheels mixed with Homebrew-clang-18 code), not the pre-existing SCF#70 pybind11 issue. That also means per-stdlib wheel variants would not have been sufficient: the axis is which libc++, not just libstdc++-vs-libc++.

The other three legs failed on the same underlying ABI bug, through a gap: NWX_ECOSYSTEM_FROM_SOURCE gates only nwx_ecosystem_dependency, while integratorxx.cmake, gauxc.cmake, gau2grid.cmake and libxc.cmake each carry their own ungated find_package(... PATHS NWX_VENV_SITE_PACKAGES) branch. IntegratorXX therefore still resolved from the installed wheels — the published nwchemex-scf wheel bundles lib/libintegratorxx.so exporting _ZN12IntegratorXX18radial_from_stringESs (old ABI) while SCF wants NSt7__cxx11. The hundreds of undefined references collapsed to exactly that one symbol.

Real fix remains moving the Linux wheel build to manylinux_2_28.