[cmake] Do not link libpython under OSX but resolve symbols using '-undefined dynamic_lookup'

-Adjust python_and_numpy target accordingly
-Adjust add_cpp2py_module accordingly

Author: Wentzell

cmake/Cpp2PyConfig.cmake.in

@@ -93,10 +93,6 @@ macro(add_cpp2py_module)
     LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
   )
 
-  if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
-    target_link_libraries(${module_name} "-undefined dynamic_lookup")
-  endif()
-
   # Keep a list of every module target.
   # Usage : e.g.  Documentation top target depends on them being built first
   set_property(GLOBAL APPEND PROPERTY CPP2PY_MODULES_LIST ${module_name})

cmake/FindPython.cmake

@@ -134,7 +134,13 @@ ENDFUNCTION(EXEC_PYTHON_SCRIPT)
 
  # Define python_and_numpy interface target
  add_library(python_and_numpy INTERFACE)
- target_link_libraries(python_and_numpy INTERFACE ${PYTHON_LIBRARY} "${PYTHON_EXTRA_LIBS}")
+ if(CMAKE_SYSTEM_NAME MATCHES "Darwin")
+   # On OSX missing python symbols should be resolved at runtime through '-undefined dynamic_lookup'
+   # as the interperter shipped with e.g. anaconda provides all relevant symbols statically
+   target_link_libraries(python_and_numpy INTERFACE "-undefined dynamic_lookup" "${PYTHON_EXTRA_LIBS}")
+ else()
+   target_link_libraries(python_and_numpy INTERFACE ${PYTHON_LIBRARY} "${PYTHON_EXTRA_LIBS}")
+ endif()
  target_include_directories(python_and_numpy SYSTEM INTERFACE ${PYTHON_INCLUDE_DIRS} ${PYTHON_NUMPY_INCLUDE_DIR})
  target_compile_options(python_and_numpy INTERFACE -Wno-register) # Some version of Python.h still use register
 

cpp2py/CMakeLists.txt

@@ -56,10 +56,6 @@ macro(add_cpp2py_module)
     LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
   )
 
-  if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
-    target_link_libraries(${module_name} "-undefined dynamic_lookup")
-  endif()
-
   # Keep a list of every module target.
   # Usage : e.g.  Documentation top target depends on them being built first
   set_property(GLOBAL APPEND PROPERTY CPP2PY_MODULES_LIST ${module_name})