GetMessage（）破坏了我的堆栈？

Question

I have had the following function used in a variety of different programs for many years. It has always worked without error. That is until now, when for the first time I attempted to make it work targeting 64bit code.

I try stepping through the code line by line... first of all I execute the line something_done = TRUE; which (obviously) sets something_done to 1... which I monitor in the "watch" window. Then I execute GetMessage (&msg, NULL, 0, 0); ... but somehow during its execution, the variable something_done gets set to zero! Subsequently the code then breaks out of the loop and , upon returning from the function call the compiler reports "Run-Time Check Failure #2 - Stack around the variable 'msg' was corrupted."

I'm not sure where to go from here.

void process_messages_until_idle()
{
    MSG msg;
    int something_done;
    int temp;

    for (;;)
    {
        something_done = FALSE;

        temp = PeekMessage(&msg,NULL,0,0,PM_NOREMOVE);

        if (temp)
        {
            something_done = TRUE;
            GetMessage (&msg, NULL, 0, 0);
            TranslateMessage (&msg);
            DispatchMessage (&msg);
        }

        if (!something_done)
        {
            break;
        }
    }
}

UPDATE: I changed something_done into a static and now the program crashes somewhere else entirely - in a place that make more sense, so this will probably be easier to debug.

Answer 1

Although there was a message when you did PeekMessage, something may have changed.

if (GetMessage(&msg, NULL, 0, 0) > 0) {
        something_done = TRUE;
        TranslateMessage (&msg);
        DispatchMessage (&msg);
}

Answer 2

I had this error on an x64 conversion of a project. Turned out to be that we had /Zp1 struct member alignment on our project and this was changing the size of the MSG struct from 48 bytes to 40 which then caused stack corruption (and likely other unrealized issues) on x64. Under Win32 it worked fine.

Answer 3

You are corrupting your stack somewhere. Check which message you were processing at the time the stack was corrupted and inspect its code to see how it breaks.