Character strings when calling Fortran from C++

[Intel_C_Intel]

How can I call the following Fortran subroutine:

subroutine runcmd(command)
character*256 command
...
Do something ....
...
return
end

from C++ (VC++ 6)

When calling it like this:

extern "C" { void __stdcall RUNCMD(char* command); }
RUNCMD("This is at test");

I get the following compiler error message:

unresolved external Symbol _RUNCMD@4

I now that it has something to do with a hidden length argument,
passed with characters, but don't know what's to do.

Thanks in advance

[Jugoslav_Dujic]

Yes, hidden length argument is passed (by default, immediately after string argument.) You should either add and additional length argument in C declaration:

extern "C" { void __stdcall RUNCMD(char* command, int len); }

or adjust the Fortran routine so that it doesn't expect length:

subroutine runcmd(command) 
!DEC$ATTRIBUTES REFERENCE:: command 
character*256 command

HTH
Jugoslav