The first dimension of zero is acceptable, and the allocation function is called. The behavior is undefined if the value in the first dimension (converted to integral or enumeration type if needed) is negative. The following behavior-changing defect reports were applied retroactively to previously published C++ standards. These operators are sometimes implemented as friend functions.
In some implementations a static_assert is used to make sure this is the case. Overloads of operator new and operator new with additional user-defined parameters (“placement forms”, versions (11-14)) may be declared at global scope as usual, and are called by the matching placement forms of new expressions. If ptr 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. 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). The destructor must be accessible from the point where the delete-expression appears.
std::remove
- Overloaded operators that are member functions can be declared static.
- If the file is currently open by any process, the behavior of this function is implementation-defined.
- These operators are sometimes implemented as friend functions.
- If the behavior of a deallocation function does not satisfy the default constraints, the behavior is undefined.
If the shared pointer p owns a deleter of type cv-unqualified Deleter (e.g. if it was created with one of the constructors that take a deleter as a parameter), then returns a pointer to the deleter. Performs contextual conversion to bool, user-defined classes that are intended to be used in boolean contexts could provide only operator bool and need not overload operator!. Creates and initializes objects with dynamic storage duration, that is, objects whose lifetime is not necessarily limited by the scope in which they were created.
Canonical implementations
The selected deallocation function must be accessible from the point where the delete-expression appears, unless the deallocation function is selected at the point of definition of the dynamic type’s virtual destructor. For a placement allocation function, the matching deallocation function must have the same number of parameter, and each parameter type except the first is identical to the corresponding parameter type of the allocation function (after parameter transformations). Attempts to allocate requested number of bytes, and the allocation request can fail (even if the requested number of bytes is zero). These allocation functions are called by new expressions to allocate memory in which new object would then be initialized. If the implementation is allowed to introduce a temporary object or make a copy of any argument as part of the call to the allocation function, it is unspecified whether the same object is used in the call to both the allocation and deallocation functions.
Rarely overloaded operators
Some implementations (e.g. MSVC before VS 2019 v16.7) require non-zero array allocation overhead on non-allocating placement array new if the element type is not trivially destructible, which is no longer conforming since CWG issue 2382. During an evaluation of a constant expression, a call to an allocation function is always omitted. Only new expressions that would otherwise result in a call to a replaceable global allocation function can be evaluated in constant expressions. When a user-defined class overloads the function call operator operator(), it becomes a FunctionObject type.
Exceptions
All deallocation functions are noexcept(true) unless specified otherwise in the declaration. However, when these operators appear in expressions, they still require an object of class type. The new expression allocates storage by calling the appropriate allocation function. If type is a non-array type, the name of the function is operator new. If type is an array type, the name of the function is operator new.
Itanium C++ ABI requires that the array allocation overhead is zero if the element type of the created array is trivially destructible. If new-initializer is a braced-enclosed initializer list, and the first dimension is potentially evaluated and not a core constant expression, the semantic constraints of copy-initializing a hypothetical element of the array from an empty initializer list are checked. The returned pointer is valid at least as long as there remains at least one shared_ptr instance that owns it. A pointer to void cannot be deleted because it is not a pointer to an object type. Destroys object(s) previously allocated by the new-expression and releases obtained memory area.
The behaviors of non-punctuation operators are described in their own respective pages. Unless otherwise specified, the remaining description in this page does not apply to these functions. Customizes the C++ operators for operands of user-defined types. If the file is currently open by any process, the behavior of this function is implementation-defined. POSIX systems unlink the file name (directory entry), but the filesystem space used by the file is not reclaimed while it is open in any process and while other hard links to the file exist.