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castinglong-integerhwnd

long to HWND (VS8 C++)

How can I cast long to HWND (C++ visual studio 8)?

Long lWindowHandler;
HWND oHwnd = (HWND)lWindowHandler;

But I got the following warning:

warning C4312: 'type cast' : conversion from 'LONG' to 'HWND' of greater size

Thanks.

Solution

  • HWND is a handle to a window. This type is declared in WinDef.h as follows:

    typedef HANDLE HWND;

    HANDLE is handle to an object. This type is declared in WinNT.h as follows:

    typedef PVOID HANDLE;

    Finally, PVOID is a pointer to any type. This type is declared in WinNT.h as follows:

    typedef void *PVOID;

    So, HWND is actually a pointer to void. You can cast a long to a HWND like this:

    HWND h = (HWND)my_long_var;

    but very careful of what information is stored in my_long_var. You have to make sure that you have a pointer in there.

    Later edit: The warning suggest that you've got 64-bit portability checks turned on. If you're building a 32 bit application you can ignore them.