Question

hello i want to get startet with programming with WIN32, therefore i wrote a programm that creates a process but in the line of code where i create the process the programm gets an error an dosn’t work (abend). i don’t know if the code in programm 1 is wrong or the code in the second programm that should be created by the first. ( I don’t know if the code in the first programm after “createprocess” is right because i didn’t get further with debugging, because in this line i get the error.(i tested it without the cout,waitforobject and close handle but i didn’t work either )).

First Programm:

#include <iostream>
#include <windows.h>
#include <string>

using namespace std;

void main()
{

bool ret;
bool retwait;

STARTUPINFO startupinfo;
GetStartupInfo (&startupinfo);

PROCESS_INFORMATION pro2info;

    ret = CreateProcess(NULL, L"D:\\betriebssystemePRA1PRO2.exe", NULL, NULL, false, CREATE_NEW_CONSOLE, NULL,
        NULL, &startupinfo, &pro2info);


    cout<<"hProcess: "<<pro2info.hProcess<<endl;
    cout<<"dwProcessId: "<<pro2info.dwProcessId <<endl;

    retwait= WaitForSingleObject (pro2info.hProcess, 100);
    retwait= WaitForSingleObject (pro2info.hProcess, 100);

    CloseHandle (pro2info.hProcess);//prozesshandle schließen 

    retwait= WaitForSingleObject (pro2info.hProcess, 100);



ExitProcess(0);


} 

Seconde Programm:

#include <iostream>
#include <windows.h>
#include <string>

using namespace std;

void main()
{


    int b;

    b=GetCurrentProcessId();

    cout<<b<<endl;
    cout<<"Druecken Sie Enter zum Beenden"<<endl;
    cin.get();
        //warten bis Benutzer bestätigt

    Sleep (700);
    ExitProcess(0);

    cout<<"test";
}

Thanks in advance

Answer 1

Notice the type of the lpCommandLine parameter to CreateProcess — it is LPTSTR, not LPCTSTR, i.e. it is not const.

This means that CreateProcess reserves the right to actually modify the contents of lpCommandLine. However, you have provided a pointer to a string literal as parameter, and string literals are immutable (they come from your program’s read-only data segment and attempts to alter them will typically result in an access violation error.)

To fix this, simply change your code not to use an immutable string literal:

wchar_t wcsCommandLine[] = L"D:\\betriebssystemePRA1PRO2.exe";
ret = CreateProcess(NULL, wcsCommandLine, NULL, NULL, ...

Interestingly enough, CreateProcessW (UNICODE) attempts to write to lpCommandLine whereas CreateProcessA (ANSI) does not, and surprise — your first program is built as UNICODE (were you to build it as ANSI it would work out of the box, at least on Windows XP.)

I can confirm that, with the above modification, your code works.

Also note that:

• unless you need to specify D:\\betriebssystemePRA1PRO2.exe‘s window title, position etc. you do not need to supply a STARTUPINFO structure at all, you can simply pass lpStartupInfo as NULL and a default will be used
• you should not be calling WaitForSingleObject on a closed handle