loaduserlibrary in DLL

This is clearly a question for Flexsim.
I have checked "flexsimrunnerexports.txt" and the function "loaduserlibrary" should be available in the DLL. So I implemented it in the Flexsimfuncs.h with:

DECLARE_FLEXSIM_FUNCTION(loaduserlibrary)

and

typedef fsnode* (*_loaduserlibrary)(string Filename, fsnode* View, int reloadmedia, int changeitemcurrent, int autoinstall);

But when I call the function I get exception errors. I call it as follows:

loaduserlibrary( FileName, NULL, 1, 0, 1);

Filename is a string and I checked this function in the scriptwindow and it works so the filename and path are correct.

What have I done wrong?

The problem is that a string class is being passed across dll boundaries. It has to do with the allocation/deallocation of memory. The dll contains its own "heap" of memory that is separate from the exe's "heap". When the dll calls a function that's implemented on the exe's side, and passes a string as a parameter, the string's constructor method is called by the dll, which means it allocates memory on the dll's heap, while the string's destructor method is called (after the function is finished) on the exe's side, which means the memory is assumed to be deallocated from the exe's heap. Since it's allocated and deallocated on different heaps, this causes an exception. Hence all functions available to dll's must take/return char*'s instead of strings.

As for a work-around, for now I'd say see if you can call a flexscript nodefunction from the dll, and then call loaduserlibrary() from the flexscript.

Anthony

Hi Anthony,

Thanks, I already implemented the work around, I was just wondering if I did something wrong.

So I guess we just have to wait for the next release

Steven