It is defined from __w4. |
Any typedef that has __w64 on it must be 32 bits on x86 and 64 bits on x64. To detect portability issues by using versions of the Visual C++ compiler earlier than Visual Studio 2010, the __w64 keyword should be specified on any typedefs that change size between 32 bit and 64 bit platforms. For any such type, __w64 must appear only on the 32-bit definition of the typedef. https://msdn.microsoft.com/en-us/library/s04b5w00.aspx |