vtordisp pragma

Controls the addition of the hidden vtordisp construction/destruction displacement member. The vtordisp pragma is C++-specific.


#pragma vtordisp( [ push, ] n )
#pragma vtordisp(pop)
#pragma vtordisp()
#pragma vtordisp( [ push, ] { on | off } )


Pushes the current vtordisp setting on the internal compiler stack, and sets the new vtordisp setting to n. If n isn't specified, the current vtordisp setting is unchanged.

Removes the top record from the internal compiler stack, and restores the vtordisp setting to the removed value.

Specifies the new value for the vtordisp setting. Possible values are 0, 1, or 2, corresponding to the /vd0, /vd1, and /vd2 compiler options. For more information, see /vd (Disable Construction Displacements).

Equivalent to #pragma vtordisp(1).

Equivalent to #pragma vtordisp(0).


The vtordisp pragma is applicable only to code that uses virtual bases. If a derived class overrides a virtual function that it inherits from a virtual base class, and if a constructor or destructor for the derived class calls that function using a pointer to the virtual base class, the compiler might introduce extra hidden vtordisp fields into classes with virtual bases.

The vtordisp pragma affects the layout of classes that follow it. The /vd0, /vd1, and /vd2 compiler options specify the same behavior for complete modules. Specifying 0 or off suppresses the hidden vtordisp members. Turn off vtordisp only if there's no possibility that the class's constructors and destructors call virtual functions on the object pointed to by the this pointer.

Specifying 1 or on, the default, enables the hidden vtordisp members where they're necessary.

Specifying 2 enables the hidden vtordisp members for all virtual bases with virtual functions. #pragma vtordisp(2) might be necessary to ensure correct performance of dynamic_cast on a partially constructed object. For more information, see Compiler Warning (level 1) C4436.

#pragma vtordisp(), with no arguments, restores the vtordisp setting to its initial setting.

#pragma vtordisp(push, 2)
class GetReal : virtual public VBase { ... };
#pragma vtordisp(pop)

See also

Pragma directives and the __pragma and _Pragma keywords