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codder88

GetWindowLong problem

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I have this

wndProc = (WNDPROC)GetWindowLong(hwnd, GWL_WNDPROC);
DWORD error = GetLastError();

error is ERROR_ALREADY_EXISTS

Why this? :(

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If you call a function and that function doesn't say it failed then GetLastError could contain anything. You should be checking the return code returned by GetWindowLong and if it fails only then should you check GetLastError.

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Quote:
Original post by nobodynews
If you call a function and that function doesn't say it failed then GetLastError could contain anything. You should be checking the return code returned by GetWindowLong and if it fails only then should you check GetLastError.


wndProc is 0

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You should use the GetWindowLongPtr Function instead, though if you're compiling for 32-bit it shouldn't make a difference. Also make sure that hwnd is a valid window-handle.

Are you doing something like this and get a wndProc of 0?
WNDPROC wndProc = (WNDPROC)GetWindowLongPtr(hwnd, GWLP_WNDPROC);
if(wndProc == NULL) {
DWORD error = GetLastError();
}

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