Thread: Explicit dynamic linking

Try enclose your function in an extern "C"{} block...it look like your compiler is mangling the name of the func and stopping the function being located....

When your compiler sees a function in C++ it "mangles" the name to provide extra information about the function (IE param size & type etc - this helps stuff like class membership and overloading)...

Therefore when GetProcAddress looks for the function, it doesnt find that name...and as each compiler is allowed by the standard to produce its own form of namemangling (life would be so much easier if the mangling itself were part of the standard) - there's no uniform API to allow you to export a c++ function.....

Therefore to allow your function to be found by GetProcAddress, it needs C linkage

fordy, when i use dynamic link libraries i dont need to use C linkage. why does mkyong have to? heres the source:

Code:

//library.cpp
#include <windows.h>
#include <stdio.h>
#define DLL_EXPORT
#include "library.h"

int bitFlag[8]={1,2,4,8,16,32,64,128};	//Bit flags for binary operations

void Notify(HWND hwnd,LPCTSTR str)
{
	MessageBox(hwnd,str,"Notification",MB_OK);
	return;
}

void Notify(HWND hwnd,long int num)
{
	char *chTemp;

	chTemp=(char *)malloc(11);
	ltoa(num,chTemp,10);

	Notify(hwnd,chTemp);

	free(chTemp);
	return;
}

int GetBit(BYTE byte,int bit)
{
	if ( (bit<0)||(bit>7) )
	{
		Notify(NULL,"bit request error; \nmust be between 0 and 7");
		exit(ERR_GETBIT);
	}

	if (byte&bitFlag[bit])
		return 1;
	
	return 0;
}

void SetBit(BYTE &byte,int bit,int state)
{
	if (GetBit(byte,bit))
	{
		if (state)
			return;
		else
			byte-=bitFlag[bit];
		return;
	}
	
	if (state)
		byte+=bitFlag[bit];
	else
		return;
	return;

}

char *BinaryString(BYTE byte)
{
	char *tmpStr;

	tmpStr=(char *)malloc(9);
	for (int i=0;i<8;i++)
		tmpStr[7-i]=GetBit(byte,i)+48;

	tmpStr[8]=0;

	return tmpStr;
}

Code:

//library.h
#ifndef libraryH
#define libraryH

#ifndef DLL_EXPORT
#define DS __declspec(dllimport) 
#else 
#define DS __declspec(dllexport)
#endif

#define ERR_GETBIT 101

void DS Notify(HWND,LPCTSTR);
void DS Notify(HWND,long int);

int DS GetBit(BYTE,int);
void DS SetBit(BYTE,int,int);
char DS *BinaryString(BYTE);

#endif

how is it different?

Originally posted by bennyandthejets
fordy, when i use dynamic link libraries i dont need to use C linkage. why does mkyong have to? heres the source:

how is it different?

Because you will be implicitly linking via the created .lib file....all clients of your dll will need that lib file and more often than not it will require a specific compiler...add to that that and material changes to the dll (size as well as export list) will require a new library to be used...therefore all your clients must now re-link their programs.......

The OP was using explicit linking via the GetProcAddress API function...and so for that, C Linkage is needed...

The best of both worlds can be found with COM.....with that you can keep your dll code in object form...you dont need a lib (as your dll should be self registering)......and as long as the interfaces implemented dont change, you can add more interfaces and/or code without the clients recompiling....

i understood basically nothing of what you just said. do know of any tutorials/sites about this stuff? im a real beginner with libraries.

Originally posted by bennyandthejets
i understood basically nothing of what you just said. do know of any tutorials/sites about this stuff? im a real beginner with libraries.

Well...I wasnt trying to be too complex......

Try http://msdn.microsoft.com/library/de...it_linking.asp for a good start...also there are loads of decent tuts on the web

My favorite reference for dlls was a chapter in Advanced Windows by Jeff Richter

thanks fordy. dont worry, you weren't being too complex, im just a lazy moron.