How to stop EnumWindows running infinitely win32

Question

The code worked all along. Somehow I manage to get Visual C++ Express not hit the break point on the final return statement and it appeared to run for ever.

In the example code bellow EnumWindows enumerates infinitely. How can one make it stop after all windows has been enumerated.

#include <Windows.h>

BOOL CALLBACK EnumWindowsProc(HWND hWnd, long lParam) {
    TCHAR buff[255];

    if (IsWindowVisible(hWnd)) {
     GetWindowText(hWnd, (LPWSTR) buff, 254);
     printf("%S\n", buff);
    }
    return TRUE;
}

int _tmain(int argc, _TCHAR* argv[]) {
    EnumWindows(EnumWindowsProc, 0);
    return 0;
}

Answer 1

From the documentation:

EnumWindows continues until the last top-level window is enumerated or the callback function returns FALSE.

To continue enumeration, the callback function must return TRUE; to stop enumeration, it must return FALSE.

Answer 2

Your code works for me, once I removed the wide-character stuff and added #include <stdio.h> to get the printf() declaration. What output does it produce on your system?

The code that works for me is:

#include <windows.h>
#include <stdio.h>

BOOL CALLBACK EnumWindowsProc(HWND hWnd, long lParam) {
    char buff[255];

    if (IsWindowVisible(hWnd)) {
        GetWindowText(hWnd, (LPSTR) buff, 254);
        printf("%s\n", buff);
    }
    return TRUE;
}

int main() {
    EnumWindows(EnumWindowsProc, 0);
    return 0;
}

Answer 3

hmm, i don't get why it would. i ran it and it worked just fine. it displayed all of the windows i have and then stopped. enumWindows will stop when either the enumWindowsProc returns false (you have it coded to always return true) or when it runs out of top-level windows to enumerate. -don

Answer 4

EnumWindowsProc should never run infinitely.

It should run until:

• Your callback returns FALSE
• There are no more top level windows to enumerate

So I suspect it appears to be running infinitely for you because of memory corruption or a memory access violation.

Your printf should be using %s not %S.

BOOL CALLBACK EnumWindowsProc(HWND hWnd, long lParam) {
    TCHAR buff[255];

    if (IsWindowVisible(hWnd)) {
        GetWindowText(hWnd, (LPWSTR) buff, 254);
        printf("%s\n", buff);//<--- %s means use TCHAR* which is WCHAR* in your case
    }
    return TRUE;
}

Also you shouldn't need to be casting your buff as a LPWSTR. If your buff is somehow a CHAR buffer then you need to compile with the Unicode character set.