Re: Use of C++

["Peter Hopfgartner" <hopfgartner@xxxxxxxxxxxxx>]

Ronny Glöckner wrote:

> Dear Werner
>
> We have some mathematical tools in C++ (called "diffpack"). We would like to
> include this in some TRNSYS components. Do you have any recommendations on
> how to to this. All other components that we have made are in fortran. Could
> we call a C++ subroutine (in a dll) from a fortran file and then link this
> to TRNSYS.
>
> Any suggestions on solutions and thing sto read are most welcome.
>
> Regards
>
> Ronny Glöckner
> _______________________________________________________________
> Ronny Glöckner - Research Scientist, PhD  tlf(w) +47 63 80 61 68
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Usually there are some points that zou must consider when mixing C/C++ 
with Fortran. Try to look how your Fortran-compiler handels function and 
variable names. Then try to figure out how your Fortran compiler passes 
function arguments.

The following applies to Fortran 77 compilers. I don't know how Fortran 
95 compilers behave and if C++ classes can be accessed from Fortran 95.

Many compilers handle your Fortran function "MyFunc" as "myfunc_" or 
"MYFUNC_": They add a trailing underscore and make everything uppercase 
or lowercase.

Function arguments are usually passed by pointer.

You must follow the rules of your compiler in order to make yout 
functions visible to the Fortran compiler.

Then the most important thing is that your prototypes should be exported 
with "export C" in order to tell your linker that you want to follow 
C-linking conventions, which is understood by every compiler on your system.

Last not least, you must not export C++ construts, but C constructs: 
make your classes accessible by C functions that pass everything by 
reference and not by value.

Peter