FORTRAN dll interfacing with C++ and other FORTRAN dlls

[cfann61]

I have a fortran dll 'X' which is called both by a C++ dll and other fortran dlls.

The fortran dlls interface with each other easily.

If I try to have the C dll call X, I get the 'unresolved external _X@24' error. I'm trying to call from C:

X(int, double, double, double*)

I can force X to pass values in this format (int, double, and double by VALUE; double* by REFERENCE), but then the other fortran dlls cannot access X, I get the 'unresolved external __imp_X@'

How are all the values passed if I do not manipulate the VALUE/REFERENCE compiler options?

Is there a way I can define the 'X' function in C so that it will call X correctly without manipulating the compiler options in X?

BTW, my work around for this was to create anintermediate fortran dll wich I've set the VALUE/REFERENCE compiler options, then called X from there. I would like to get rid of the intermediate dll.

Thanks

Chris

[Steven_L_Intel1]

It would appear that your C code has declared X as __stdcall, thus the @24. Intel Fortran, by default, doesn't use STDCALL. If you show us the entire declaration of X in the C code we can suggest how to change it. This has nothing to do with value/reference. However, your declaration of X does have the first two arguments passed by value. If you changed all of the arguments to *int or *double, and passed addresses (&arg) rather than just the arg value, then it would work without changes in the Fortran. There is no way to avoid changing one or the other.

[cfann61]

I have used STDCALL do define the function in C like this:

extern "C" void _stdcall STMPROP(int * runoption, double * pressure, double * temperature, double * RET);

I am also passing addresses with &

Is there a way to define it in C to avoid making changes to the fortran dll?

[Steven_L_Intel1]

Take out the __stdcall for a start.

[cfann61]

That did the trick.

Thanks

[cfann61]

How would I define a string in the routine?

I was thinking link this:

extern "C" void STMPROP(char * string, int strlen);

Haven't tried this yet, just curious.

[Steven_L_Intel1]

Rather than int, use size_t. Also, all the string lengths go at the end of the argument list, so if you had two arguments, a string and a real, it would look something like this:

extern "C" void SUB(char * string, float *r, size_t strlen);

This assumes you are not using the C interoperability features of Fortran.