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pointers-to-members.md

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description Learn more about the pointers_to_members pragma directive in Microsoft C/C++
title pointers_to_members pragma
ms.date 01/22/2021
f1_keywords
pointers_to_members_CPP
vc-pragma.pointers_to_members
helpviewer_keywords
class members, pointers to
pragma, pointers_to_members
members, pointers to
pointers_to_members pragma
no-loc
pragma

pointers_to_members pragma

C++ Specific

Specifies whether a pointer to a class member can be declared before its associated class definition. Used to control the pointer size, and the code required to interpret the pointer.

Syntax

#pragma pointers_to_members( pointer-declaration [ , most-general-representation ] )

Remarks

You can place a pointers_to_members pragma in your source file as an alternative to using the /vmb or /vmg compiler options or the inheritance keywords.

The pointer-declaration argument specifies whether you've declared a pointer to a member before or after the associated function definition. The pointer-declaration argument is one of the following two symbols:

Argument Comments
full_generality Generates safe, sometimes nonoptimal code. You use full_generality if any pointer to a member is declared before the associated class definition. This argument always uses the pointer representation specified by the most-general-representation argument. Equivalent to /vmg.
best_case Generates safe, optimal code using best-case representation for all pointers to members. Requires defining the class before declaring a pointer to a member of the class. The default is best_case.

The most-general-representation argument specifies the smallest pointer representation that the compiler can safely use to reference any pointer to a member of a class in a translation unit. The argument can be one of these values:

Argument Comments
single_inheritance The most general representation is single-inheritance, pointer to a member function. Causes an error if the inheritance model of a class definition for which a pointer to a member is declared is ever either multiple or virtual.
multiple_inheritance The most general representation is multiple-inheritance, pointer to a member function. Causes an error if the inheritance model of a class definition for which a pointer to a member is declared is virtual.
virtual_inheritance The most general representation is virtual-inheritance, pointer to a member function. Never causes an error. virtual_inheritance is the default argument when #pragma pointers_to_members(full_generality) is used.

Caution

We advise you to put the pointers_to_members pragma only in the source code file that you want to affect, and only after any #include directives. This practice lessens the risk that the pragma will affect other files, and that you will accidentally specify multiple definitions for the same variable, function, or class name.

Example

//   Specify single-inheritance only
#pragma pointers_to_members( full_generality, single_inheritance )

END C++ Specific

See also

Pragma directives and the __pragma and _Pragma keywords