Why is Examining or Using 'this' After 'delete this' Undefined Behavior in C ?

When Does the Undefined Behavior of "delete this" Begin?

In C , "delete this" is a construct that has several restrictions listed in the C FAQ. While the first three restrictions seem reasonable, the fourth restriction prohibits any examination, comparison, printing, or casting of this value after deletion. This article explores why this restriction exists.

The Mysterious "this" Value

After calling "delete this," the value of "this" becomes undefined, rendering any subsequent actions involving it unpredictable. While certain compilers may behave sensibly, the C specification does not prevent unexpected or even catastrophic consequences from occurring.

Undefined Behavior: A Pitfall to Avoid

Undefined behavior in programming is generally discouraged, even when a particular compiler handles it as expected. The unpredictable nature of such behavior can lead to unexpected results or even system failure.

Workaround for Avoiding Undefined Behavior

To circumvent this issue, consider creating a copy of the pointer (as an integer) before invoking "delete this." This workaround preserves the value of "this" while adhering to the restrictions imposed on it after deletion.

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