External functions: Calling a C script that use external Library

Question

I am trying to call an external C code that use GLPK (GNU Linear Programming Kit) within my Modelica model. The C code works just fine, have tested it in a stand alone mode where all the inputs are self-supplied. When I tried to link it with my Modelica model, it starts to give me linker-type error, that is similar to below:

examples.SimpleSystemOptimalDispatch_functions.c:(.text+0x99d): undefined reference to `glp_set_row_bnds'

I notice that to run the C code in a stand alone mode, a special linker has to be used

gcc standalonecode.c -lglpk -o standalone

I believe the problem is in linking process, but I fail to grasp how to tell Modelica to do the link automatically. Any idea how to solve this linking problem in Modelica?

Thank you and best wishes

Answer 1

I managed to solve the problem.

What I did was:

1. Compile the glpk.h located in /usr/local/include/ using

gcc -c glpk.h -o libglpk.o

2. Using @ReinstateMonica answer, I made my .c file into .so

gcc -fPIC -shared -lglpk -o liblinprog.so st_linprog.c

3. In my function.mo in my Modelica, I put annotation as follow

annotation(Library ={"linprog","glpk"},
           LibraryDirectory="modelica://SolarTherm/Resources/Include/lib");

What I understood is that since my st_linprog.c is depending on libglpk, then in order for Modelica to be able to run using libglpk, I have to compile glpk.h and convert st_linprog.c to shared library. During the st_linprog.c conversion into shared library, -lglpk flag makes sure that the shared library is linked to libglpk (I think).

If you guys have more elegant approach kindly share it here! Cheers,

Phil