Calling Fortran DLL from C++ using Visual Studio 2008

[rocket_man]

I am have troubles getting a simple example to make a C++ program call Fortran functions from a Fortran DLL. Here is a description of what I have done, please help me do it right:

1) Created a new Intel Fortran project, a blank DLL (using Visual Studio 2008)

2) wrote a simple Fortran program: (fortfunc.F90)

subroutine FR1(N,M)

M=N*N

return

end

integer function FF1(N)

FF1=N*N*N

return

end

3) I compiled it using visual studio 2008 and it created the appropriate DLL (fortfunc.dll)

4) I created another new project, C++ window32 console blank project

5) wrote a simple C++ program to call the fortran functions

#include

using namespace std;

extern "C" {

void __stdcall FR1(int *a, int *b);

int __stdcall FF1(int *c);

}

int main() {

int n = 10,nSq,nCube;

FR1(&n,&nSq);

cout << "The square is:" << nSq << endl;

nCube=FF1(&n);

cout << "The cube is:" << nCube << endl;

return 0;

}

5) I moved the fortfunc.dll to the same folder where my main.cpp exists

6) from the property->Linker->inputs->Additional Dependencies I added the fortfunc.dll

note: I also tried adding the whole directory path and got the same results

7) now I tried to compile the C++ and here is the error:

>Compiling...

1>main.cpp

1>Linking...

1>fortfunc.dll : fatal error LNK1107: invalid or corrupt file: cannot read at 0x2F8

1>Build log was saved at "file://c:\\projects\\sandbox\\test2\\test2\\Release\\BuildLog.htm"

1>test2 - 1 error(s), 0 warning(s)

My question is pretty simple, what is the correct to add the dll so the C++ can call the fortran functions?

Thank you

[Steven_L_Intel1]

1. You are missing !DEC$ ATTRIBUTES DLLEXPORT directives for FR1 and FF1
2. You should not use __stdcall when calling Intel Fortran (unless you have changed the default convention.)
3. You do not add a .DLL as a linker dependency - you add the .LIB created when the DLL was built. But because of #1, you have no .LIB

[rocket_man]

Where do I need to put the !DEC$ ATTRIBUTES DLLEXPORT? and how should I call the fortran functions? (to the best of my knowledge I have not changed any of the default conventions).

Thanks

[Steven_L_Intel1 · Accepted solution]

[fortran]subroutine FR1(N,M)
!DEC$ ATTRIBUTES DLLEXPORT :: FR1

M=N*N

return

end

 

integer function FF1(N)
!DEC$ ATTRIBUTES DLLEXPORT :: FF1

FF1=N*N*N

return

end[/fortran]

Just remove the __stdcall from your C++ code - the rest looks ok to me.

[rocket_man]

Awesome! That worked.

I would however note that the fortran libraries need to be included when using Visual Studio 2008. Not sure why this doesn't happen automatically but here is what I found worked:

properties->Linker->General->Additional Library Directories->""

[Steven_L_Intel1]

That's if the main program is not Fortran. See Configuring for Mixed Language Applications.

[polarbear00]

I have exactly same question as the one you answered, however when I try to add "Dll1.lib" to below location
***properties->Linker->General->Additional Library Directories->""***
it seeks "folder" and not "file" (so that i can add "Dll1.lib"). I copied both Dll1.lib and Dll1.dll in Debug folder of the VC++ 2010 solution where the .exe file is yet it did not work.
I copied the whole VC++ and IVF codes at the end. when i build it I get below errors:

3 IntelliSense: #error directive: Please use the /MD switch for _AFXDLL builds
1 error LNK2019: unresolved external symbol _Dll1 referenced in function "public: void __thiscall CSDI1View::OnToolsDependent(void)" (?OnToolsDependent@CSDI1View@@QAEXXZ)
2 error LNK1120: 1 unresolved externals



******************************* Compiled in IVF *********
subroutine Dll1(a)
implicit none
!DEC$ ATTRIBUTES DLLEXPORT, STDCALL, REFERENCE :: Dll1
!DEC$ ATTRIBUTES ALIAS:'Dll1' :: Dll1
Doubleprecision :: a
a=5.5;
return
end !subroutine Dll1

******************************** Call from VC++ in Visual Studio 2010 *****
#include "iostream"
using namespace std;
....

extern "C" void Dll1(double *a);
void CSDI1View::OnToolsDependent()
{
CDependentDlg Dlg;
Dlg.DoModal();
double a;
a=35;
Dll1(&a);

}

Thanks

[Steven_L_Intel1]

You want to add the library to "Additional Dependencies". Or, the way I like to do it, add the library as a "source file" to the project.

You don't want to say STDCALL. Try this:

subroutine Dll1(a) BIND(C,NAME="Dll1")
implicit none
!DEC$ ATTRIBUTES DLLEXPORT :: Dll1
Doubleprecision :: a
a=5.5;
return
end !subroutine Dll1

On the C++ side, I'm not really sure what the error is about - perhaps you specified static libraries?

[polarbear00]

I just realized that my IVF evalusation license expired and no longer can change the fortran code. I added the .lib as source file and still I am getting same errors in VC++. Here "You don't want to say STDCALL. Try this:" you mean that if I don't want to use _stdcall in VC++ I can change the fortran code the way you recommended?
By the way I am persuaded to buy Latest IVF with MKL and IMSL for the company I work at. I have two computers here though, one laptop windows 7 64 bit and one desktop XP 32 bit. would the IVF be compatible with both?

Thanks

[Steven_L_Intel1]

I did not see __stdcall in your C++ declaration, so you don't want to use STDCALL in Fortran.

Yes, the Intel compiler works with both of those confgurations.

[polarbear00]

Thanks Steve, it was resolved.

[Deb_M_]

I am working on a mixed language projoject. I am going to develo an windows form application using C# on visual studio 2010. Would you please help me on the following problems:

1> I have "c" codes whcich  calls fortran functions and sub routines

2> I have fortan functions/subroutines which calls "c" codes  

3> I want to make dll from the above codes and want to use them in my windows form application using C# under visual studio

How do I compile the c and fortran code to make dll ( both 32/64 bit) for using them in C# code. How to setup visual studio 2010. Please help me with two prototype examples (c/fortran c# and fortran/c c# ) which can handle two-dimensional array.

Thanks

Deb

[Steven_L_Intel1]

Deb, this would be better as a separate topic - calling from C# is very different from C++, and there are additional issues that need to be addressed.