std::ranges::construct_at

Since C++20

Header: <memory>

Creates a T object initialized with the arguments in args at given address location.

# Declarations

Call signature

template< class T, class... Args >
constexpr T* construct_at( T* location, Args&&... args );

(since C++20)

# Parameters

location: pointer to the uninitialized storage on which a T object will be constructed
args...: arguments used for initialization

# Return value

location

# Notes

std::ranges::construct_at behaves exactly same as std::construct_at, except that it is invisible to argument-dependent lookup.

# Example

#include <iostream>
#include <memory>
 
struct S
{
    int x;
    float y;
    double z;
 
    S(int x, float y, double z) : x{x}, y{y}, z{z} { std::cout << "S::S();\n"; }
 
    ~S() { std::cout << "S::~S();\n"; }
 
    void print() const
    {
        std::cout << "S { x=" << x << "; y=" << y << "; z=" << z << "; };\n";
    }
};
 
int main()
{
    alignas(S) unsigned char buf[sizeof(S)];
 
    S* ptr = std::ranges::construct_at(reinterpret_cast<S*>(buf), 42, 2.71828f, 3.1415);
    ptr->print();
 
    std::ranges::destroy_at(ptr);
}

# Defect reports

DR	Applied to	Behavior as published	Correct behavior
LWG 3436	C++20	construct_at could not create objects of array types	can value-initialize bounded arrays
LWG 3870	C++20	construct_at could create objects of cv-qualified types	only cv-unqualified types are permitted