Calling a function from a FORTRAN DLL using C++ code - c++

Question

I want to load a fortran dll in C++ code and call a function in the fortran dll.
Following is the code
SUBROUTINE SUB1()
PRINT *, 'I am a function '
END
After creation of the foo.dll [fotran dll ] this is the folowing C++ code in visual studio 2012 that I have written to load the fortran dll .
and call the function SUB1 in the fortran code
#include <iostream>
#include <fstream>
#include <Windows.h>
using namespace std;
extern "C" void SUB1();
typedef void (WINAPI *PGNSI)(LPSYSTEM_INFO);
int main(void)
{
LoadLibrary(L"foo.dll");
PGNSI pGNSI = (PGNSI) GetProcAddress(GetModuleHandle(TEXT("foo.dll")),"SUB1");
return 0;
}
While running the I am getting the following error:
The program can't start because libgcc_s_dw2-1.dll is missing from your computer.
Try reinstalling the program to fix this problem.
Is this the correct way of calling the dll from C++ ?
I am very new to this fortran dll . Please help me regarding this.

Answer 1

First of all you need to export the function like this...
!fortcall.f90
subroutine Dll1() BIND(C,NAME="Dll1")
implicit none
!DEC$ ATTRIBUTES DLLEXPORT :: Dll1
PRINT *, 'I am a function'
return
end !subroutine Dll1
Create the dll using following command
gfortran.exe -c fortcall.f90
gfortran.exe -shared -static -o foo.dll fortcall.o
After that, place the libgcc_s_dw2-1.dll, libgfortran-3.dll and libquadmath-0.dll in the application path of VS. OR you can add the PATH to environment.
After that, you can call the FORTRAN exposed function from VS like below...
#include <iostream>
#include <Windows.h>
using namespace std;
extern "C" void Dll1();
typedef void(* LPFNDLLFUNC1)();
int main(void)
{
HINSTANCE hDLL;
LPFNDLLFUNC1 lpfnDllFunc1; // Function pointer
hDLL = LoadLibrary(L"foo.dll");
if (hDLL != NULL)
{
lpfnDllFunc1 = (LPFNDLLFUNC1)GetProcAddress(hDLL,"Dll1");
if (!lpfnDllFunc1)
{
// handle the error
FreeLibrary(hDLL);
return -1;
}
else
{
// call the function
lpfnDllFunc1();
}
}
return 0;
}