Compiling 32-bit vs 64-bit project using CMake

Question

How do I specify that CMake should use a different link_directories value depending on whether the target is 32-bit is 64-bit? For example, 32-bit binaries need to link with 32-bit Boost, 32-bit binaries need to link with 64-bit Boost.

Answer 1

You do something along these lines

  if( CMAKE_SIZEOF_VOID_P EQUAL 8 )
    set( BOOST_LIBRARY "/boost/win64/lib" )
  else( CMAKE_SIZEOF_VOID_P EQUAL 8 )
    set( BOOST_LIBRARY "/boost/win32/lib" )
  endif( CMAKE_SIZEOF_VOID_P EQUAL 8 )
  set( CMAKE_EXE_LINKER_FLAGS ${BOOST_LIBRARY} )

Answer 2

For Boost specifically, you should use

FIND_LIBRARY(Boost 1.44 COMPONENTS ...)

Then the CMake variable Boost_LIBRARY_DIRS will contain the correct library path, which has to be set using LINK_DIRECTORIES, e.g.

LINK_DIRECTORIES(${Boost_LIBRARY_DIRS})

The more general case is correctly described in user434507's answer.