C++Talk.NET

andreas.kratzsch@freenet. · Guest

Hi,

i habe a simple C/C++ question:
How can i access external variables inside a dll ?
For example:

main module:

int x; // extern !

void func();

int main()
{
x = 0;
func();
return x;
}

dll module:

extern int x;

void func()
{
// do somthing with x
x = 3;
}

I tried to use __declare(dllimport/dllexport) also,
but the linker always complains about the unresolved symbol x.
If i use /FORCE to create the dll the linker doesn't
resolve the symbol when the dll is loaded.
(Visual C++ 6)

Thanks !

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ravinderthakur@gmail.com · Guest

the procedure for using the same is as follows:

in the header file having decratation of the variable , declare the
variable with dllexport
specification.
on compiling a .lib file will be created.
add the .lib file and the header file to the project for the dll.
now compile and link.

this should work.

thanks
rt

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Kodt · Guest

//////////////
// your_dll.h
#pragma once

// the selector of appropriate declspec
#ifdef YOUR_DLL_IMPL // this macro is defined when compiling the DLL
#define YOUR_DLL_API __declspec(dllexport)
#else // all others will import
#define YOUR_DLL_API __declspec(dllimport)
#endif

extern // tells that this is a declaration, not definition
int YOUR_DLL_API x;

////////////////
// your_dll.cpp

#define YOUR_DLL_IMPL // or set up your project / makefile
#include "your_dll.h"
// to be sure the definition matches to the declaration

int x = 123; // the definition

BOOL WINAPI DllMain(bla bla bla) { ..... }

////////////////
// your_exe.cpp

#include "your_dll.h" // include the dll's declarations
#pragma comment(lib,"your_dll") // tell the linker to use your_dll
// or set up your project/solution settings,
// or add "/link your_dll.lib" to the command line

int main() { return x; }

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