Compiler Warning C4972
Collapse the table of content
Expand the table of content
Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here. ArchiveDisclaimer

Compiler Warning C4972

Error Message

Directly modifying or treating the result of an unbox operation as an lvalue is unverifiable

Dereferencing a handle to a value type, also known as unboxing, and then assigning to it is not verifiable.

For more information, see Implicit Boxing.


The following sample generates C4972.

// C4972.cpp
// compile with: /clr:safe
using namespace System;
ref struct R {
   int ^ p;   // a value type

int main() {
   R ^ r = gcnew R;
   *(r->p) = 10;   // C4972

   // OK
   r->p = 10;
   Console::WriteLine( r->p );
   Console::WriteLine( *(r->p) );
© 2016 Microsoft