Calling fortran code from Qt in QtCreator

Question

I have a nice GUI that I've designed using QtCreator that I want to use to call functions from a Fortran source file to do all the backend work. My QtCreator version is 2.7.0 based on Qt 5.0.1 I wrote a simple fortran-90 program in a file named sum.f90 to add two numbers:

integer function addup (a, b)
implicit none
  integer a, b
addup = a + b
  return
end

Then i added this sum.f90 file to the .pro file in sources like so :

SOURCES += forsum.f90

Then I created a header file fortranlink.h containing the following lines :

extern "C"
{
    extern int addup_(int*,int*);
}

Then I included this header file in my main source file "#include fortranlink.h", and called this addup_ function like :

int a=2;
int b=3;
int result=addup_(&a,&b);

After compilation, I get the following errors :

Undefined reference to _gfortran_st_write
Undefined reference to _gfortran_transfer_character_write
Undefined reference to _gfortran_transfer_integer_write
Undefined reference to _gfortran_st_write_done

These errors probably occur because I am not linking in the standard fortran libraries using -lgfortran somewhere. But where do I use it ?

Answer 1

The answer by @cageman is correct. LIBS+=lgfortran