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/vd (Disable Construction Displacements)

/vd supports incorrect behavior in an early version of Visual C++, and is no longer needed.


/vdn
0

Suppresses the vtordisp constructor/destructor displacement member. Choose this option only if you are certain that all class constructors and destructors call virtual functions virtually.

1

Enables the creation of hidden vtordisp constructor/destructor displacement members. This choice is the default.

2

Allows you to use dynamic_cast Operator on an object being constructed. For example, a dynamic_cast from a virtual base class to a derived class.

/vd2 adds a vtordisp field when you have a virtual base with virtual functions. /vd1 should be sufficient. The most common case where /vd2 is necessary is when the only virtual function in your virtual base is a destructor.

These options apply only to C++ code that uses virtual bases.

Visual C++ implements C++ construction displacement support in situations where virtual inheritance is used. Construction displacements solve the problem created when a virtual function, declared in a virtual base and overridden in a derived class, is called from a constructor during construction of a further derived class.

The problem is that the virtual function may be passed an incorrect this pointer as a result of discrepancies between the displacements to the virtual bases of a class and the displacements to its derived classes. The solution provides a single construction displacement adjustment, called a vtordisp field, for each virtual base of a class.

By default, vtordisp fields are introduced whenever the code defines user-defined constructors and destructors and also overrides virtual functions of virtual bases.

These options affect entire source files. Use vtordisp to suppress and then re-enable vtordisp fields on a class-by-class basis.

To set this compiler option in the Visual Studio development environment

  1. Open the project's Property Pages dialog box. For details, see How to: Open Project Property Pages.

  2. Click the C/C++ folder.

  3. Click the Command Line property page.

  4. Type the compiler option in the Additional Options box.

To set this compiler option programmatically

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