Gurobi and C++- How it works together using Clion - c++

Question

First of all I am complete new to C++, so if you know the answer please be patient with me ;). Here my problem:
I wanna solve an IP with Gurobi in a C++ Code. The Code itself seems fine since there are no expression marked as errors. However when I run the Code I get the following error report:
Undefined symbols for architecture x86_64:
and many lines like that:
"GRBLinExpr::GRBLinExpr(GRBVar, double)", referenced from:
bridge_problem::max_flow_lp(time_expanded_network&, lemon::ListDigraph&, lemon::DigraphExtender<lemon::ListDigraphBase>::ArcMap<int>&, lemon::DigraphExtender<lemon::ListDigraphBase>::ArcMap<int>&, lemon::DigraphExtender<lemon::ListDigraphBase>::NodeMap<int>&) in bridge_problem.cpp.o
I suppose that the mistake is in my CMakeList.txt file. This file was automatically created since I am using Clion and for including gurobi I entered those additional lines:
include_directories(/Library/gurobi604/mac64/include)
link_directories(/Library/gurobi604/mac64/lib/libgurobi_c++.a)
link_directories(/Library/gurobi604/mac64/lib/libgurobi60.so)
Any help is greatly appreciated and if you need any more information just let me know. (In case it is important I using a mac).
EDIT: I changed my make code since I found this one:
https://github.com/joschu/trajopt/blob/master/cmake/modules/FindGUROBI.cmake
I changed the version since I have gurobi604 but it still does not work. My new error message is:
fatal error: 'gurobi_c++.h' file not found #include "gurobi_c++.h"
I don't get it since I thought by
find_path(GUROBI_INCLUDE_DIR
NAMES gurobi_c++.h
PATHS "$ENV{GUROBI_HOME}/include"
"/Library/gurobi604/mac64/include"
"C:\\libs\\gurobi604\\include"
)
that should be easy to find. Any suggestion?

Answer 1

From the small excerpt of your CMakeLists.txt, I expect you should be using target_link_libraries rather than link_directories.
I'd normally recommend linking to the static version of any library rather than the shared if possible (i.e. in this case prefer "libgurobi_c++.a" over "libgurobi60.so" assuming they're the same library, just compiled differently).
So, if your exe is called MyExe, you could do:
target_link_libraries(MyExe /Library/gurobi604/mac64/lib/libgurobi_c++.a)
Also, it's almost always best to avoid specifying hard-coded paths in your CMakeLists.txt. Although your copy of "libgurobi_c++.a" lives in "/Library/gurobi604/mac64/lib/", that won't be the case for other users, or on different platforms.
You can avoid this by having CMake "find" the library, for example by calling find_library:
find_library(Gurobi NAMES gurobi_c++)
if(NOT Gurobi)
message(FATAL_ERROR "Failed to find Gurobi lib. Try setting CMAKE_PREFIX_PATH")
endif()
target_link_libraries(MyExe ${Gurobi})
Then, when you run CMake, you just need to tell it where the Gurobi library is. I'm not sure how you do that in CLion, but for example if you were running CMake from the command line, you'd do:
cmake . -DCMAKE_PREFIX_PATH=/Library/gurobi604/mac64