Pragma Import_Function (GNAT Reference Manual) (original) (raw)

2.79 Pragma Import_Function ¶

Syntax:

pragma Import_Function ( [Internal =>] LOCAL_NAME, [, [External =>] EXTERNAL_SYMBOL] [, [Parameter_Types =>] PARAMETER_TYPES] [, [Result_Type =>] SUBTYPE_MARK] [, [Mechanism =>] MECHANISM] [, [Result_Mechanism =>] MECHANISM_NAME]);

EXTERNAL_SYMBOL ::= IDENTIFIER | static_string_EXPRESSION

PARAMETER_TYPES ::= null | TYPE_DESIGNATOR {, TYPE_DESIGNATOR}

TYPE_DESIGNATOR ::= subtype_NAME | subtype_Name ' Access

MECHANISM ::= MECHANISM_NAME | (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION})

MECHANISM_ASSOCIATION ::= [formal_parameter_NAME =>] MECHANISM_NAME

MECHANISM_NAME ::= Value | Reference

This pragma is used in conjunction with a pragma Import to specify additional information for an imported function. The pragmaImport (or equivalent pragma Interface) must precede theImport_Function pragma and both must appear in the same declarative part as the function specification.

The Internal argument must uniquely designate the function to which the pragma applies. If more than one function name exists of this name in the declarative part you must use the Parameter_Types andResult_Type parameters to achieve the required unique designation. Subtype marks in these parameters must exactly match the subtypes in the corresponding function specification, using positional notation to match parameters with subtype marks. The form with an 'Access attribute can be used to match an anonymous access parameter.

You may optionally use the Mechanism and Result_Mechanismparameters to specify passing mechanisms for the parameters and result. If you specify a single mechanism name, it applies to all parameters. Otherwise you may specify a mechanism on a parameter by parameter basis using either positional or named notation. If the mechanism is not specified, the default mechanism is used.