how to use a static library?

lazuli_beast

In MS Visual Studio, I created a fortran library 'Lib1' containing 'Source1.f90':

subroutine fortfunc(ff)
real*4 ff

write(6,100) ff
100 format('ff=',f6.3)

return
end

I compiled it (x86) and it created a Lib1.lib file.

In Qt Creator I opened the openglwindow example and added to main.cpp

#include <iostream>
using namespace std;
extern "C" {
    void fortfunc_(float *ff);
}

and inside the main function

    float ff = 6.6;
    fortfunc_(&ff);

In the .pro file I right clicked and added Lib1 as a static library.

When I try to build the linker has an error:

main.obj : error LNK2019: unresolved external symbol _fortfunc_ referenced in function _main

Where did I go wrong? Thanks

Christian Ehrlicher

You also have to link against this library -> for qmake see LIBS

lazuli_beast

@Christian-Ehrlicher Ok, I figured it would take care of that for me. I added this line to my pro file and I get the same error

win32:LIBS += C:\Users\[myname]\source\repos\Lib1\Lib1\Debug\Lib1.lib

Christian Ehrlicher

Please try with forward slashes as shown in the documentation. Are you sure this libs exports the symbol in this way? Your function is named fortfunc in fortran but fortfunc_ in your c++ source.

lazuli_beast

@Christian-Ehrlicher Ah, I didn't notice the slashes - that's fixed. I tried changing the function name to fortfunc in the c++ but it still has a problem with unresolved symbol.
How can I tell what the actual name is in the exported library? Thanks

Christian Ehrlicher

@lazuli_beast said in how to use a static library?:

How can I tell what the actual name is in the exported library? Thanks

Don't know - ask fortran guys how to export/import a fortran function.

lazuli_beast

Thanks so much for your help getting this far. After some googling I found an example I was able to follow to finally get it working.
First, I changed my fortran to use the iso_c_binding. This lets you set the function name that you will call in the c++ program.

subroutine fortfunc(ff) bind(c, name="fortfunc_bind")
    use, intrinsic :: iso_c_binding
    implicit none
    
    real*4 ff

    write(6,100) ff
    100 format('ff=',f6.3)

    return
end subroutine

I got a different error, you have to also add the fortran library to the Qt project. In my case:

win32:LIBS += -L"C:/Program Files (x86)/IntelSWTools/compilers_and_libraries_2020.4.311/windows/compiler/lib/ia32_win"