macOS Build Fails with `ld: library 'xc' not found`

[dustinrb]

On macOS in a new virtual environment, building PySCF-Forge from source by running

export CMAKE_CONFIGURE_ARGS="-DCMAKE_C_COMPILER=gcc-14 -DCMAKE_CXX_COMPILER=g++-14"
pip install git+https://github.com/pyscf/pyscf-forge.git

results in a linker error (build.log log for full output)

      [ 90%] Linking C shared library /private/var/folders/1j/0rqv9z_52f11z6t_rcrxr2sh0000gn/T/pip-req-build-q3p68ef0/pyscf/lib/libxc_itrf2.dylib
      ld: warning: search path '/usr/local/lib64' not found
      ld: library 'xc' not found
      collect2: error: ld returned 1 exit status
      make[2]: *** [/private/var/folders/1j/0rqv9z_52f11z6t_rcrxr2sh0000gn/T/pip-req-build-q3p68ef0/pyscf/lib/libxc_itrf2.dylib] Error 1
      make[1]: *** [CMakeFiles/clib_libxc_itrf2.dir/all] Error 2
      make[1]: *** Waiting for unfinished jobs....

Since PySCF is a build and runtime dependency, Pip is using a temporary installation of PySCF for linking. I don't think this is necessarily and issue, make debugging slightly more complicated.

Work-Around

Use a copy of LibXC provided by Homebrew by setting

export LIBRARY_PATH="/opt/homebrew/lib"
export C_INCLUDE_PATH="/opt/homebrew/include"
export CPLUS_INCLUDE_PATH="/opt/homebrew/lib"

See https://github.com/MatthewRHermes/mrh?tab=readme-ov-file#installing-on-macos

Hacky Fix

I cloned PySCF-Forge and built from the local source. After installing PySCF ls $VIRTUAL_ENV/lib/python3.13/site-packages/pyscf/lib/deps/lib shows

libcint.6.dylib*  libxc.15.dylib*   libxcfun.2.dylib*

In the PySCF-Forge, changing the line

target_link_libraries (clib_libxc_itrf2 xc ${OPENMP_C_PROPERTIES})
# Change to
target_link_libraries (clib_libxc_itrf2 "xc.15" ${OPENMP_C_PROPERTIES})

in pyscf-forge/pyscf/lib/CMakeLists.txt fixes the issue after running pip install ./pyscf-forge; however, this not the right solution.

This may be a quirk in how .dylibs are linked. Probably the correct fix would be to use find_package(LibXC) tell CMake to favor the PySCF provided version. I don't mind working on this, but I wanted to get some feedback first.

System Specs

macOS Sequoia v15.5
Compiler GCC-14 from Homebrew to avoid OpenMP issues.
Python 3.9, 3.13
PySCF-Forge from master
PySCF from PyPi and master

Thanks for your help!

[jeanwsr]

I believe the path to pyscf's libxc for ld has been handled in

pyscf-forge/pyscf/lib/CMakeLists.txt

Lines 97 to 100 in ef4e548

	link_directories(${PYSCF_SOURCE_DIR}/lib/deps/lib ${PYSCF_SOURCE_DIR}/lib/deps/lib64)
	link_directories(${PYSCF_SOURCE_DIR}/lib)
	link_directories(${CMAKE_INSTALL_PREFIX}/lib ${CMAKE_INSTALL_PREFIX}/lib64)
	message(STATUS "${PYSCF_SOURCE_DIR}/lib may need to be put in the environment LD_LIBRARY_PATH")

So it will look for libxc in the pyscf source dir (can be temporary path created by pip). And this works on linux. With pip install git+URL -v I can see

  -- Include pyscf source dir: /tmp/pip-build-env-19_1v5p6/overlay/lib/python3.9/site-packages/pyscf
  -- /tmp/pip-build-env-19_1v5p6/overlay/lib/python3.9/site-packages/pyscf/lib may need to be put in the environment LD_LIBRARY_PATH

So the question here is why this does not work on macOS. Maybe has something to do with the rpath handling here

pyscf-forge/pyscf/lib/CMakeLists.txt

Lines 102 to 113 in ef4e548

	# See also https://gitlab.kitware.com/cmake/community/wikis/doc/cmake/RPATH-handling
	if (WIN32)
	#?
	elseif (APPLE)
	set(CMAKE_BUILD_WITH_INSTALL_RPATH TRUE)
	set(CMAKE_INSTALL_RPATH "@loader_path;@loader_path/deps/lib;@loader_path/deps/lib64")
	set(CMAKE_BUILD_RPATH "@loader_path;@loader_path/deps/lib;@loader_path/deps/lib64")
	else ()
	set(CMAKE_SKIP_BUILD_RPATH True)
	set(CMAKE_BUILD_WITH_INSTALL_RPATH True)
	set(CMAKE_INSTALL_RPATH "\$ORIGIN:\$ORIGIN/deps/lib:\$ORIGIN/deps/lib64")
	endif ()

which was copied from pyscf.

[jeanwsr]

If you want to use libxc outside pyscf source dir, like the homebrew one, you need to use -DCMAKE_INSTALL_PREFIX as discussed in #97 .