Unhandled Error with CreateProcess [duplicate] - c++

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CreateProcess method ends up with an error
(1 answer)
Closed 6 years ago.
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.

Answer 1

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.

Answer 2

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.