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Unhandled error with CreateProcess

I was reading about the CreateProcess function in C ++ and I wanted to try it. The main idea of ​​the code is to have my main one execute another process (notepad). Indeed, this is just basic code. When I run the program, I get:

First Chance Exception at 0x752bb763 in createprocess.exe: 0xC0000005: Location where access violation was written 0x00be57b8.
Unhandled exception at 0x752bb763 in createprocess.exe: 0xC0000005: Location where access violation was written 0x00be57b8.

When I make a breakpoint where the error occurs, I end up in tidtable.c (as far as thread access is concerned, I think). In particular, tidtable.c in CRTIMP PFLS_GETVALUE_FUNCTION __cdecl __set_flsgetvalue()

I really don't know what and how to avoid this problem. The error is thrown when CreateProcess is called (ie, it never outputs "from created").

My code:

#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.

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2 answers


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

If you specify it as a string, as you did, it is a constant string and the function, when 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 can also read this blog post .

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The second argument to CreateProcess cannot be a constant or literal string because func is trying to modify a string. Copy the literal to a local array and then pass it as the second argument.



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