Thread: DLL issue

For reference for others:

Code:

#include "stdafx.h"
#include <stdio.h> // for namespace
#include <valarray> // for Xor 
#include <string>

BOOL APIENTRY DllMain( HANDLE hModule, 
					  DWORD ul_reason_for_call, 
					  LPVOID lpReserved
					  )
{
	return TRUE;
}

char outvalue[2] = "";
char out [2] = "";

__declspec(dllexport) LPCTSTR ecc(LPCTSTR invalue)
{
	unsigned int v=0;
	unsigned int vlen=0;

	// Setup Values of Variables 
	vlen = strlen(invalue);
	outvalue[0] = invalue[0];

	// Loop
	for(v;v<vlen-1;v++)
	{ 
		outvalue [0] ^= invalue[v+1]; 
	}
	sprintf(out, "&#37;X",2, outvalue[0]);

	return out;
}

As a first suggestion, I'd like to advise to get rid of LPCTSTR and the like. In your functions, use appropriate type.
The function should take const char* and return char*. OK? Good.
Then you will need to allocate a buffer large enough to hold the new data via new.
Then you simply assign the XORed data to your new buffer and return it.

Start with that.