Difference between revisions of "cpp/memory/construct at"
From cppreference.com
m (→Notes) |
m (relocate) |
||
| Line 16: | Line 16: | ||
}} | }} | ||
except that {{tt|construct_at}} may be used in evaluation of [[cpp/language/constant expression|constant expressions]]. | except that {{tt|construct_at}} may be used in evaluation of [[cpp/language/constant expression|constant expressions]]. | ||
| + | |||
| + | While called in the evaluation of some expression {{c|e}}, {{tt|construct_at}} prevents {{c|e}} from being a constant expression if {{tt|p}} points to neither storaged obtained by {{c|std::allocator<T>::allocate}} nor an object whose lifetime began within the evaluation of {{c|e}}, or underlying initialization does not meet the requirements of constant evaluation. | ||
===Parameters=== | ===Parameters=== | ||
| Line 25: | Line 27: | ||
===Return value=== | ===Return value=== | ||
{{tt|p}} | {{tt|p}} | ||
| − | |||
| − | |||
| − | |||
===Example=== | ===Example=== | ||
Revision as of 22:26, 6 February 2020
| Defined in header <memory>
|
||
| template<class T, class... Args> constexpr T* construct_at( T* p, Args&&... args ); |
(since C++20) | |
Creates a T object initialized with arguments args... at given address p. This overload participates in overload resolution only if ::new(std::declval<void*>()) T(std::declval<Args>()...) is well-formed in evaluated context.
Equivalent to
return ::new (const_cast<void*>(static_cast<const volatile void*>(p))) T(std::forward<Args>(args)...);
except that construct_at may be used in evaluation of constant expressions.
While called in the evaluation of some expression e, construct_at prevents e from being a constant expression if p points to neither storaged obtained by std::allocator<T>::allocate nor an object whose lifetime began within the evaluation of e, or underlying initialization does not meet the requirements of constant evaluation.
Contents |
Parameters
| p | - | pointer to the uninitialized storage on which a T object will be constructed
|
| args... | - | arguments used for initialization |
Return value
p
Example
| This section is incomplete Reason: no example |
See also
| [static] |
constructs an object in the allocated storage (function template) |
| (C++17) |
destroys an object at a given address (function template) |
