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salamander1965 · Guest

I'm trying to move code from a class in the main application into a
package, but am running into 'unresolved external' linker errors.
I've done OK in the past with declaring package functions properly so
they can be called from the main app, but I can't figure out how to
modify the declarations in this case. Any suggestions would be
appreciated.

Here's an abbreviated form of the code:

///MAINUNIT.H///
class Module {
private:
int FCurrChar;
int __fastcall GetCurrentChar(void);
public:
__property int CurrChar = {read=GetCurrentChar};
};

///MAINUNIT.CPP///
#include "MAINUNIT.H"
#include "PACKAGE.H"

int __fastcall Module::GetCurrentChar(void) {
return FCurrChar;
}

///PACKAGE.H///
extern "C" __stdcall PACKAGE void PkgFunc(Module* ModPtr);

///PACKAGE.CPP///
#include "MAINUNIT.H"

void __stdcall PkgFunc(Module* ModPtr) {
int MainCurrChar=ModPtr->CurrChar;
}

I'm trying to compile the package at this point. The compilation goes
OK, but the linker complains about 'unresolved external
Module::GetCurrentChar referenced from ...'

I've #included MAINUNIT.H in the package .cpp, so it knows the
structure of the Module class, and it can dereference ModPtr passed as
a parameter. But it doesn't know what to do about the GetCurrentChar
function back in the main app accessed through the CurrChar property,
and I have not been able to figure out where to put 'extern', or if
other modifiers might be needed. Also, does the main app have
anything equivalent to an import library that the linker can use to
resolve the external references?

BTW: Although it's not shown in the shortened example, PkgFunc() is
itself called from the main app, so I have the main app using external
functions in the package, and the package using external classes in
the main app.

Thanks -- salamander

salamander1965 · Guest

After thinking on it for awhile, is it even possible to access
variables/functions in an executable from a package using the usual
'extern' way of doing things; or is this where callback functions
passed as pointers to the package functions are useful?

If it is possible, I'm not sure how the linker could ever resolve the
external references since (as far as I know) compiling a .exe does not
produce any kind of import library-type file the linker could use.

Am I looking at this the right way?

-- salamander

Remy Lebeau (TeamB) · Guest

"salamander1965" <salamander1 (AT) verizon (DOT) net> wrote

Remy Lebeau (TeamB) · Guest

"salamander1965" <salamander1 (AT) verizon (DOT) net> wrote

salamander1965 · Guest