Question

The following code prints the desired output but it prints garbage at the end of the string. There is something wrong with the last call to MultiByteToWideChar but I can’t figure out what. Please help??

#include "stdafx.h"
#include<Windows.h>
#include <iostream>
using namespace std;
#include<tchar.h>

int main( int, char *[] )
{
    TCHAR szPath[MAX_PATH];
    if(!GetModuleFileName(NULL,szPath,MAX_PATH))
    {cout<<"Unable to get module path"; exit(0);}

    char ansiStr[MAX_PATH];
    if(!WideCharToMultiByte(CP_ACP,WC_COMPOSITECHECK,szPath,-1,
        ansiStr,MAX_PATH,NULL,NULL))
    {cout<<"Unicode to ANSI failed\n";
    cout<<GetLastError();exit(1);}

    string s(ansiStr);

    size_t pos = 0;

    while(1)
    {
        pos = s.find('\\',pos);
        if(pos == string::npos)
            break;
        s.insert(pos,1,'\\');
        pos+=2;
    }

    if(!MultiByteToWideChar(CP_ACP,MB_PRECOMPOSED,s.c_str(),s.size(),szPath,MAX_PATH))
    {cout<<"ANSI to Unicode failed"; exit(2);}

    wprintf(L"%s",szPath);
}

Answer 1

MSDN has this to say about the cbMultiByte parameter:

If this parameter is -1, the function processes the entire input
string, including the terminating null character. Therefore, the
resulting Unicode string has a terminating null character, and the
length returned by the function includes this character.

If this parameter is set to a positive integer, the function processes
exactly the specified number of bytes. If the provided size does not
include a terminating null character, the resulting Unicode string is
not null-terminated, and the returned length does not include this
character.

..so if you want the output string to be 0 terminated you should include the 0 terminator in the length you pass in OR 0 terminate yourself based on the return value…