Fix Windows wheel build for free-threaded Python#219
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…d PYBIND11_NEWPYTHON The free-threaded CPython 3.14 (cp314t) build on Windows fails with: LINK : fatal error LNK1104: cannot open file 'python314.lib' The root cause is that PYBIND11_NEWPYTHON is deprecated/unrecognized in pybind11 3.0.x, causing it to fall back to FindPythonLibsNew.cmake which doesn't properly handle the 't' suffix for free-threaded Python on Windows. PYBIND11_FINDPYTHON is the correct variable that tells pybind11 to use CMake's modern FindPython module, which correctly handles free-threaded Python library naming (python314t.lib vs python314.lib). Co-authored-by: dfm <350282+dfm@users.noreply.github.com>
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[WIP] Fix windows wheel build issue
Fix Windows wheel build for free-threaded Python
Mar 15, 2026
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The
cp314t-win_amd64wheel build fails withLINK : fatal error LNK1104: cannot open file 'python314.lib'because pybind11 3.x doesn't recognize the deprecatedPYBIND11_NEWPYTHONvariable, falls back toFindPythonLibsNew.cmake, and that module doesn't handle thetsuffix for free-threaded Python on Windows.The build logs even tell us the fix:
PYBIND11_NEWPYTHONwithPYBIND11_FINDPYTHONinCMakeLists.txtso pybind11 uses CMake'sFindPythonmodule, which correctly resolvespython314t.libWarning
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