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Destroys object(s) previously allocated by thenew-expression and releases obtained memory area.
Contents |
::(optional)delete expression | (1) | ||||||||
::(optional)delete[]expression | (2) | ||||||||
| expression | - | one of the following:
|
Given the pointer evaluated fromexpression (after possible conversions) asptr.
The result of the delete-expression always has typevoid.
If the object being deleted has incomplete class type at the point of deletion,and the complete class has a non-trivial destructor or a deallocation function, the behavior is undefined(until C++26)the program is ill-formed(since C++26).
Ifptr is not a null pointer and thedeallocation function is not a destroying delete(since C++20), the delete-expression invokes thedestructor (if any) for the object that is being destroyed, or for every element of the array being destroyed (proceeding from the last element to the first element of the array). The destructor must beaccessible from the point where the delete-expression appears.
After that, whether or not an exception was thrown by any destructor, the delete-expression invokes thedeallocation function: eitheroperator delete (first version) oroperator delete[] (second version), unless the matching new-expression was combined with another new-expression(since C++14).
The deallocation function's name islooked up in the scope of the dynamic type of the object pointed to byptr, which means class-specific deallocation functions, if present, are found before the global ones. If:: is present in the delete-expression, only the global namespace is examined by this lookup. In any case, any declarations other than of usual deallocation functions are discarded.
If any deallocation function is found, the function to be called is selected as follows (seedeallocation function for a more detailed description of these functions and their effects):
| (since C++20) |
| (since C++17) |
| (since C++14) |
The selected deallocation function must beaccessible from the point where the delete-expression appears, unless the deallocation function is selected at the point of definition of thedynamic type’svirtual destructor.
The pointer to the block of storage to be reclaimed is passed to thedeallocation function that was selected by the process above as the first argument. The size of the block is passed as the optionalstd::size_t argument.The alignment requirement is passed as the optionalstd::align_val_t argument.(since C++17)
Ifptr is a null pointer value, no destructors are called, andthe deallocation function may or may not be called (it's unspecified), but the default deallocation functions are guaranteed to do nothing when passed a null pointer.
Ifptr is a pointer to a base class subobject of the object that was allocated withnew, the destructor of the base class must bevirtual, otherwise the behavior is undefined.
A pointer tovoid cannot be deleted because it is not a pointer to an object type.
Because a pair of brackets following the keyworddelete is always interpreted as the array form of a delete-expression, alambda-expression with an empty capture list immediately afterdelete must be enclosed in parentheses. // delete []{ return new int; }(); // parse errordelete([]{return newint;})();// OK | (since C++11) |
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| CWG 288 | C++98 | for the first form, the static type of the operand was compared with its dynamic type | compare the static type of the object to be deleted with its dynamic type |
| CWG 353 | C++98 | whether the deallocation function will be invoked if the destructor throws an exception was unspecified | always invoked |
| CWG 599 | C++98 | the first form could take a null pointer of any type, including function pointers | except pointers to object types, all other pointer types are rejected |
| CWG 1642 | C++98 | expression could be a pointer lvalue | not allowed |
| CWG 2474 | C++98 | deleting a pointer to an object of a similar but different type resulted in undefined behavior | made well-defined |
| CWG 2624 | C++98 | pointers obtained from non-allocating operator new[] could be passed todelete[] | prohibited |
| CWG 2758 | C++98 | it was unclear how access control was done for the deallocation function and the destructor | made clear |
