Unhandled Error with CreateProcess

Question

I was reading about CreateProcess function in c++ and I wanted to try it. Basic idea of the code is to have my main execute another process (notepad). Really, it’s just the basic code. When I run the program, I get:

First-chance exception at 0x752bb763 in createprocess.exe: 0xC0000005: Access violation writing location 0x00be57b8.
Unhandled exception at 0x752bb763 in createprocess.exe: 0xC0000005: Access violation writing location 0x00be57b8.

When I make a break point for where the error occurs, I get taken to tidtable.c (which is for accessing threads, I guess). Specifically in tidtable.c at CRTIMP PFLS_GETVALUE_FUNCTION __cdecl __set_flsgetvalue() I really don’t know what or how to avoid this problem. The error occurs with the CreateProcess call (ie, it never outputs the “out of create”).

My code is:

#include "stdafx.h"
#include <stdio.h>
#include <windows.h>
#include <strsafe.h>
#include <direct.h>
#include <string.h>
#include <conio.h>

int main(VOID)
{
    STARTUPINFO si;
    PROCESS_INFORMATION pi;

        //allocate memory
    ZeroMemory(&si, sizeof(si));
si.cb = sizeof(si);
ZeroMemory(&pi, sizeof(pi));


fprintf(stderr, "This is just a test");

//create child process
if (!CreateProcess(NULL,
    L"C:\\Windows\\Notepad.exe",
    NULL,
    NULL,
    FALSE,
    0,
    NULL,
    NULL,
    &si,
    &pi))
{
        fprintf(stderr, "create process failed");

        return -1;
}
fprintf(stderr, "out of create");

    //parent waits for child to complete
WaitForSingleObject(pi.hProcess, INFINITE);

fprintf(stderr, "after wait");

printf("Child Complete");

    //close handle
CloseHandle(pi.hProcess);
//  CloseHandle(pi.hthread);

}

If anyone knows how to overcome this problem, your help would be appreciated.

See http://blogs.msdn.com/b/oldnewthing/archive/2009/06/01/9673254.aspx I edited that into Ervin's answer. — 0xC0000022L, Apr 09 '12 at 14:24
The link to the article "Why does the CreateProcess function modify its input command line?" posted by @0xC0000022L will redirect you to its TOC. The new link is: https://devblogs.microsoft.com/oldnewthing/20090601-00/?p=18083 — li ki, May 18 '21 at 07:04

score 21 · Accepted Answer · edited Apr 09 '12 at 14:24

21

The problem is that the second parameter of the CreateProcess function is an in/out parameter.

If you specify it as a string like you did, it is a constant string and the function when it is called cannot write to the memory location, thus you have a memory access violation. The correct way is to call your function like this:

LPTSTR szCmdline = _tcsdup(TEXT("C:\\Windows\\Notepad.exe"));

//create child process
if (!CreateProcess(NULL,
    szCmdline,
    NULL,
    NULL,
    FALSE,
    0,
    NULL,
    NULL,
    &si,
    &pi))
{
    fprintf(stderr, "create process failed");

    return -1;
}

You may also want to read this blog article.

edited Apr 09 '12 at 14:24

0xC0000022L

20,597
9
86
152

answered Apr 06 '12 at 13:44

ervinbosenbacher

1,720
13
16

Now I uncommented the last line of code:CloseHandle(pi.hthread) but I get this error: error C2039: 'hthread' : is not a member of '_PROCESS_INFORMATION'. How do I fix that. And thank you – Favn Hghksd Apr 06 '12 at 14:27
1

It's a typo. CloseHandle(pi.hThread); C++ is case sensitive. So please take care of the case. – ervinbosenbacher Apr 06 '12 at 14:39
You can use intellisense to help you. – ervinbosenbacher Apr 06 '12 at 14:40
According to the documentation, only the unicode version of the function attempts to modify the string. Since you don't seem to need unicode in this case you could also explicitely use the ANSI version, CreateProcessA. – Frerich Raabe Apr 06 '12 at 14:52
Yes, that was the problem. Thanx. I will look into intellisense. – Favn Hghksd Apr 06 '12 at 14:56
I have a question now, if you don't mind: – Favn Hghksd Apr 07 '12 at 11:19

score 1 · Answer 2 · answered Apr 06 '12 at 13:46

1

The 2nd arg to CreateProcess cannot be const or a literal string because the func attempts to modify the string. Copy the literal to a local array and then pass that as the 2nd arg.

answered Apr 06 '12 at 13:46

Marc Sherman

2,303
14
22

Only true for the Unicode version! The ANSI version does not have this, because the buffer with the converted string is always writable. – 0xC0000022L Apr 09 '12 at 14:22

Unhandled Error with CreateProcess

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