// error.h

#ifndef __ERROR_H_
#define __ERROR_H_

void GetLastErrorAsString(LPTSTR msg);

#endif


// error.c
#include "error.h"

void GetLastErrorAsString(LPTSTR msg)
{
    //Get the error message, if any.
    DWORD errorMessageID = GetLastError();
    if (errorMessageID == 0)
        return NULL; //No error message has been recorded

    LPSTR messageBuffer = NULL;
    size_t size = FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL, errorMessageID, MAKELANGID(LANG_ENGLISH, SUBLANG_ENGLISH_US), (LPSTR)&messageBuffer, 0, NULL);

    lstrcpy(msg, messageBuffer);

    LocalFree(messageBuffer);
}