__int3264 attribute

The keyword __int3264 specifies an integral type that has the following properties:

  • It is 32-bit on 32-bit platforms
  • It is 64-bit on 64-bit platforms
  • It is 32-bit on the wire for backward compatibility. It gets truncated on the sending side and extended appropriately (signed or unsigned) on the receiving side.
[ signed | unsigned ] __int3264 [ int ] declarator-list;



Specifies one or more standard C declarators, such as identifiers, pointer declarators, and array declarators. (Function declarators and bit-field declarations are not allowed in structures that are transmitted in remote procedure calls. These declarators are allowed in structures that are not transmitted.) Separate multiple declarators with commas.


This type has been introduced specifically to facilitate the porting of 32-bit interfaces to 64-bit. It is generally useful only in cases where existing interfaces send pointers as integers or use similar workaround techniques. Microsoft does not recommend using this type (or other public types derived from it such as INT_PTR, DWORD_PTR) where it can be avoided. In particular, these types cannot be used in OLE Automation interfaces and type libraries. Use of this type, or types derived from it, in new interfaces is not recommended. See the Microsoft Interface Definition Language (MIDL): 64-Bit Porting Guide for more information on these issues as well as comments and advice on other 64-bit issues.

The __int3264 keyword can be preceded by either the keyword signed or the keyword unsigned. The int keyword is optional and can be omitted. To the MIDL compiler the __int3264 integer is signed by default and is synonymous with signed __int3264 int.

The __int3264 integer type is one of the base types of the IDL language. The __int3264 integer type can appear as a type specifier in const declarations, typedef declarations, general declarations, and function declarators (as a function-return-type specifier and a parameter-type specifier). For the context in which type specifiers appear, see IDL.

See also

MIDL Base Types