[CMake] RPATH for pkg-config

[Alexander Neundorf]

On 2018 M01 3, Wed 10:08:09 CET Franck Houssen wrote:
> Hello,
> 
> How to ask cmake to add a library path (coming from pc file) to rpath ?
> 
> I checked this https://cmake.org/Wiki/CMake_RPATH_handling, but still not
> working. Can somebody help ?
> >> more main.cpp
> 
> #include <petsc.h>
> 
> int main(int argc, char ** argv) {
> PetscInitialize(&argc, &argv, NULL, "");
> PetscFinalize();
> return 0;
> }
> 
> >> more CMakeLists.txt
> 
> cmake_minimum_required(VERSION 3.7)
> enable_language(CXX)
> 
> find_package(MPI REQUIRED)
> find_package(PkgConfig REQUIRED) # Get pkg_check_modules.
> pkg_check_modules(PETSc REQUIRED PETSc)
> 
> project(main)
> add_executable(main main.cpp)
> 
> target_include_directories(main PUBLIC ${MPI_CXX_INCLUDE_PATH})
> target_link_libraries(main PUBLIC ${MPI_CXX_LIBRARIES})
> 
> target_include_directories(main PUBLIC ${PETSc_INCLUDE_DIRS})
> foreach(lib ${PETSc_LDFLAGS})
> target_link_libraries(main PUBLIC ${lib})
> endforeach(lib)

How does each ${lib} look like ?
Is it "-lpetsc" or does it have the full path to the libraries ?
You should use the full path to the libraries, otherwise cmake doesn't know 
where they are and the RPATH computation will not work.

> 
> foreach(dir ${PETSc_LIBRARY_DIRS})
> link_directories(main PUBLIC ${dir}) # Not sure: is this needed ?
> endforeach(dir)

no, link_directories() in general should not be used.

> # use, i.e. don't skip the full RPATH for the build tree
> SET(CMAKE_SKIP_BUILD_RPATH FALSE)
> # when building, don't use the install RPATH already
> # (but later on when installing)
> SET(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE)
> SET(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")

If the automatic computation fails, you could add the petsc lib dir here as 
INSTALL_RPATH

Alex