How to tell CMake to find the lib in local folder through command line? - cmake

Question

I am trying to link my local version of gflags (which is in ~/mylibs/gflags) while compiling google-test. In gtest's CMakeLists.txt, it's using find_package:
if (WITH_GFLAGS)
find_package (gflags 2.2.0)
if (gflags_FOUND)
set (HAVE_LIB_GFLAGS 1)
determine_gflags_namespace (gflags_NAMESPACE)
endif (gflags_FOUND)
endif (WITH_GFLAGS)
I don't want to modify the CMakeLists.txt file. Is there anyway to tell cmake to find the package in my folder ?
Thanks!

Answer 1

The gflags documentation describes specifying the location of a non-standard installation when using CMake:
The gflags_DIR variable must be set to the <prefix>/lib/cmake/gflags directory containing the gflags-config.cmake file
In your case, this might look like:
cmake -Dgflags_DIR=/home/blackball/mylibs/gflags/lib/cmake/gflags [...]

Answer 2

Since you are integrating gflags as subproject in a super cmake, you basically want find_package() to be a no-op if you have it in your "meta-project" source dir. This can be done by overloading the find_package() command.
Top CMakeLists.txt:
# Use find_package everywhere, no-op if it's a subproject
macro(find_package)
if(NOT TARGET ${ARGV0} AND NOT TARGET ${ARGV0}::${ARGV0})
_find_package(${ARGV})
else()
if(TARGET ${ARGV0})
get_target_property(TGT_VER ${ARGV0} VERSION)
set(TGT ${ARGV0})
else()
get_target_property(TGT_VER ${ARGV0}::${ARGV0} VERSION)
set(TGT ${ARGV0}::${ARGV0})
endif()
message(STATUS "Found ${ARGV0}: CMake Target ${TGT} (found version \"${TGT_VER}\")")
set(${ARGV0}_FOUND TRUE)
endif()
endmacro()
note: for gflags you may need to "force" gflags_NAMESPACE also since gflags it's a source not a binary (cf glog issue ToDo)