To prevent the problems that implementation-dependent data types can cause on varying computer architectures, MIDL defines its own base data types:
| Base type | Description |
|---|---|
| boolean | Data item that can have the value TRUE or FALSE. |
| byte | An 8-bit data item guaranteed to be transmitted without any change. |
| char | An 8-bit unsigned character data item. |
| double | A 64-bit floating-point number. |
| float | A 32-bit floating-point number. |
| handle_t | Primitive handle that can be used for RPC binding or data serializing. |
| hyper | A 64-bit integer that can be declared as either signed or unsigned. (Can also be referred to as _int64.) |
| int | A 32-bit integer that can be declared as either signed or unsigned. |
| long | A 32-bit integer that can be declared as either signed or unsigned. |
| short | A 16-bit integer that can be declared as either signed or unsigned. |
| small | An 8-bit integer that can be declared as either signed or unsigned. |
| wchar_t | Wide-character type that is supported as a Microsoft extension to IDL. Therefore, this type is not available if you compile using the /osf switch. |
The header file RPCNDR.H provides definitions for most of these base data types. The keyword int is recognized and is remoteable on 32-bit platforms. On 16-bit platforms, the int data type requires a modifier, such as short or long, to specify its length.
Although void * is recognized as a generic pointer type by the ANSI C standard, MIDL restricts its usage. Each pointer used in a remote or serializing operation must point to either base types or types constructed from base types. (There is an exception: context handles are defined as void * types. For more information see Context Handles.)