interior_ptr (C++/CLI)

 

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An interior pointer declares a pointer to inside a reference type, but not to the object itself. An interior pointer can point to a reference handle, value type, boxed type handle, member of a managed type, or to an element of a managed array.

(There are no remarks for this language feature that apply to all runtimes.)

(There are no remarks for this language feature that apply to only the Windows Runtime.)

Requirements

Compiler option: /ZW

The following syntax example demonstrates an interior pointer.

Syntax

cli::interior_ptr<cv_qualifier type> var = &initializer;  

Parameters

cv_qualifier
const or volatile qualifiers.

type
The type of initializer.

var
The name of the interior_ptr variable.

initializer
A member of a reference type, element of a managed array, or any other object that you can assign to a native pointer.

Remarks

A native pointer is not able to track an item as its location changes on the managed heap, which results from the garbage collector moving instances of an object. In order for a pointer to correctly refer to the instance, the runtime needs to update the pointer to the newly positioned object.

An interior_ptr represents a superset of the functionality of a native pointer. Therefore, anything that can be assigned to a native pointer can also be assigned to an interior_ptr. An interior pointer is permitted to perform the same set of operations as native pointers, including comparison and pointer arithmetic.

An interior pointer can only be declared on the stack. An interior pointer cannot be declared as a member of a class.

Since interior pointers exist only on the stack, taking the address of an interior pointer yields an unmanaged pointer.

interior_ptr has an implicit conversion to bool, which allows for its use in conditional statements.

For information on how to declare an interior pointer that points into an object that cannot be moved on the garbage-collected heap, see pin_ptr.

interior_ptr is in the cli namespace. See Platform, default, and cli Namespaces for more information.

For more information on interior pointers, see

Requirements

Compiler option: /clr

Examples

Example

The following sample shows how to declare and use an interior pointer into a reference type.

// interior_ptr.cpp  
// compile with: /clr  
using namespace System;  
  
ref class MyClass {  
public:  
   int data;  
};  
  
int main() {  
   MyClass ^ h_MyClass = gcnew MyClass;  
   h_MyClass->data = 1;  
   Console::WriteLine(h_MyClass->data);  
  
   interior_ptr<int> p = &(h_MyClass->data);  
   *p = 2;  
   Console::WriteLine(h_MyClass->data);  
  
   // alternatively  
   interior_ptr<MyClass ^> p2 = &h_MyClass;  
   (*p2)->data = 3;  
   Console::WriteLine((*p2)->data);  
}  

Output

1  
2  
3  

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