lld-link error: could not open 'python37.lib' #2171
Description
Issue description
On windows, using CMake+clang to compile for windows. This means linking using lld-link.exe rather than link.exe. The argument for the python lib is being passed to lld-link as 'Python37.lib' though the file is actually 'python37.lib' (different capitalization). This wouldn't normally be a problem on windows, of course, but in this case lld-link is complaining "error : could not open 'python37.lib': no such file or directory". Confusingly, it uses the correct case in the error message.
The capitalization in question comes from FindPythonLibsNew.cmake:
if(CMAKE_HOST_WIN32 AND NOT (MSYS OR MINGW))
set(PYTHON_LIBRARY
"${PYTHON_PREFIX}/libs/Python${PYTHON_LIBRARY_SUFFIX}.lib")
# when run in a venv, PYTHON_PREFIX points to it. But the libraries remain in the
# original python installation. They may be found relative to PYTHON_INCLUDE_DIR.
if(NOT EXISTS "${PYTHON_LIBRARY}")
get_filename_component(_PYTHON_ROOT ${PYTHON_INCLUDE_DIR} DIRECTORY)
set(PYTHON_LIBRARY
"${_PYTHON_ROOT}/libs/Python${PYTHON_LIBRARY_SUFFIX}.lib")
endif()
...
Changing the section above to use lowercase 'python' rather than 'Python' fixes the problem, i.e.:
if(CMAKE_HOST_WIN32 AND NOT (MSYS OR MINGW))
set(PYTHON_LIBRARY
"${PYTHON_PREFIX}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
# when run in a venv, PYTHON_PREFIX points to it. But the libraries remain in the
# original python installation. They may be found relative to PYTHON_INCLUDE_DIR.
if(NOT EXISTS "${PYTHON_LIBRARY}")
get_filename_component(_PYTHON_ROOT ${PYTHON_INCLUDE_DIR} DIRECTORY)
set(PYTHON_LIBRARY
"${_PYTHON_ROOT}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
endif()
...
Reproducible example code
- Visual studio 2019, with the current VS-installer versions of Python (3.7.3) and (Clang 9.0.0)
- Config in CMakeSettings.json is just the x64-Clang-Debug default from visual studio.
- pybind11 installed through vcpkg, though I've also checked the issue still occurs with the current pybind11 master as a subrepo.