Re: IsWindow weirdness

From:
"Alex Blekhman" <xfkt@oohay.moc>
Newsgroups:
microsoft.public.vc.language
Date:
Sun, 6 May 2007 20:50:47 +0300
Message-ID:
<OwrWVcAkHHA.1624@TK2MSFTNGP06.phx.gbl>
"mr.sir bossman" wrote:

[Both in WM_INITDIALOG]
Asserts:
HWND ret = GetDlgItem(...);//ret = valid handle
returned
assert(::IsWindow(ret));

Doesn't Assert:
HWND ret = GetDlgItem(...);//ret = valid handle
returned
AddText(ret, "yadda, yadda");//adds text to combo
assert(::IsWindow(ret));


So, you do something bad in `AddText'. Probably
overwriting
a buffer or something like that.


Sry, I'm a newb and I can't understand how that would be
possible(overwritting text to a buffer makes a previously
invalid handle,
valid), could you please elaborate?


So I misunderstood you. I thought that first assert succeeds
but second assert fails. Anyway, here's short example of
buffer overrun:

void bar(HWND h)
{
    void* p = &h;
    memset((BYTE*)p + 100, 0, 200);
}

void foo()
{
    HWND h = GetDesktopWindow();
    assert(IsWindow(h)); // h is valid here

    bar(h);
    assert(IsWindow(h)); // h is corrupted
}

Alex

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