out

[ [function-attribute-list] ] type-specifier [pointer-declarator] function-name(
        [ out [ , parameter-attribute-list ] ] type-specifier [declarator]
        , ...
    );

function-attribute-list

Specifies zero or more attributes that apply to the function. Valid function attributes are callback, local; the pointer attribute ref, unique, or ptr; and the usage attributes string, ignore, and context_handle.

type-specifier

Specifies a base_type, struct, union, or enum type or type identifier. An optional storage specification can precede type-specifier.

pointer-declarator

Specifies zero or more pointer declarators. A pointer declarator is the same as the pointer declarator used in C; it is constructed from the * designator, modifiers such as far, and the qualifier const.

function-name

Specifies the name of the remote procedure.

parameter-attribute-list

Specifies zero or more attributes appropriate for a specified parameter type. Parameter attributes with the out attribute can also take the directional attribute out; the field attributes first_is, last_is, length_is, max_is, size_is, and switch_type; the pointer attribute ref, unique, or ptr; and the usage attributes context_handle and string. The usage attribute ignore cannot be used as a parameter attribute. Separate multiple attributes with commas.

declarator

Specifies standard C declarators, such as identifiers, pointer declarators, and array declarators. For more information, see pointers and arrays. The parameter declarator in the function declarator, such as the parameter name, is optional.

Example

HRESULT MyFunction([out] short * pcount); 
 

Remarks

The out attribute identifies pointer parameters that are returned from the called procedure to the calling procedure (from the server to the client).

The out attribute indicates that a parameter that acts as a pointer and its associated data in memory are to be passed back from the called procedure to the calling procedure.

The out attribute must be a pointer. DCE IDL compilers require the presence of an explicit * as a pointer declarator in the parameter declaration. Microsoft IDL offers an extension that drops this requirement and allows an array or a previously defined pointer type.

A related attribute, in, indicates that the parameter is passed from the calling procedure to the called procedure. The in and out attributes specify the direction in which the parameters are passed. A parameter can be defined as in-only, out-only, or in, out.

An out-only parameter is assumed to be undefined when the remote procedure is called and memory for the object is allocated by the server. Since top-level pointer/parameters must always point to valid storage, and therefore cannot be null, out cannot be applied to top-level unique or ptr pointers. Parameters that are ref pointers must be either in or in, out parameters.

See Also

in, ref