C ++流程监控（GetExitCodeProcess）

Question

I want to monitor a process in c++, so I'm using:

std::wstring windowName = TEXT("needle");
HWND windowHandle = FindWindowW(NULL, windowName.c_str());

The FindWindow function, as I understand it, checks the title for all windows (Why did Microsoft name their OS after a core part of it, checking windows in Windows, madness). If a title matches "needle" then it gives me the...

HWND windowHandle

Next I am using:

DWORD* PID;
GetWindowThreadProcessId(windowHandle, PID);
HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, *PID);

This gives me the processID or PID as I've named it. I can then use that to...

HWND p;
DWORD state;
GetExitCodeProcess(p, &state);

... get the state of the process, I'm going to check for it being "STILL_ACTIVE", like so:

        if (state != STILL_ACTIVE) {
        std::cout << "excessive profanity\n";
    }
    else {
        std::cout << "sigh of relief\n";
    }

Except this doesn't work, "cout-ing" (new verb) the value of state gives me some kind of hexadecimal code. It's never "STILL_ACTIVE" despite having multiple windows with "needle" as the title. The code compiles fine, it's just something to do with conversion, pointers, LPCWSTR's or something I've never come across. Help would be appreciated. Thanks

Answer 1

One error (and probably not the only error) is that there is no way this can work correctly:

DWORD* PID;
GetWindowThreadProcessId(windowHandle, PID);

You are giving GetWindowThreadProcessId an uninitialized pointer, PID . There is nothing that the function can do with it except dereference it (causing undefined behavior), or at best, check if the value is NULL.

When a function asks for a pointer, it doesn't mean you literally declare a pointer and pass it to the function. The function wants the address of an existing entity:

DWORD PID;
GetWindowThreadProcessId(windowHandle, &PID);

Answer 2

You have two problems:

1) As PaulMcKenzie points out in his answer, PID points to nothing, and will cause problems. Instead you should declare a DWORD and pass a pointer to it to GetWindowThreadProcessId :

DWORD PID;
// note: &PID instead of just PID
GetWindowThreadProcessId(windowHandle, &PID);
// note: Just PID instead of *PID
HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, PID);

2) GetExitCodeProcess needs a handle to a process, not an uninitialized HWND . Instead you should give it the handle returned from OpenProcess :

DWORD state;
// note: this is the hProcess returned from OpenProcess
GetExitCodeProcess(hProcess, &state);

Note that this will still only work for one process. If multiple processes have windows with the title "needle" then the result of your FindWindow call will be unpredictable.