A writefln issue or a Thread issue?

[Sam Hu]

Given below code:

module testWin32Process;

import win32.windows;//get 
from:http://www.dsource.org/projects/bindings/wiki/WindowsApi


import std.string;
import std.conv;
import std.stdio;
import core.stdc.stdlib;


string startupProcess()
{
        STARTUPINFO si;
        si.cb=si.sizeof;
        
        PROCESS_INFORMATION pi;
        char* szCommandLine=cast(char*)toStringz("cmd"/*"notepad 
testWin32Process.d"*/);
        si.dwFlags=STARTF_USESHOWWINDOW;
        si.wShowWindow=true;

        
        int bRet=CreateProcess(
                null,
                szCommandLine,
                null,
                null,
                false,
                CREATE_NEW_CONSOLE,
                null,
                null,
                &si,
                &pi);
        if(bRet)
        {
                CloseHandle(pi.hThread);
                
                return std.string.format("New process ID:%d\n"
                        "Host process ID:%d\n",
                        pi.dwProcessId,
                        pi.dwThreadId);
                
        }
        else
        {
                
                return "Do not know what happend.";//just want to check
        }
        
}
int main(string[] args)
{
        writefln("%s\n",toStringz(startupProcess)); // prints blank!!!
        
        
MessageBox(null,toStringz(startupProcess),toStringz("result?"),0);//prints 
contents as expected!!
        
        system("pause");
        return 0;
}

As commented,were I use writefln(...),it prints blank;were I use MessageBox,it 
prints well as expected:

New Process ID:2216
Host Process ID:2456

Could anybody here figure me out what the problem is?Thanks in advance.

Regards,
Sam