std::stack<T,Container>::emplace

template< class... Args > void emplace( Args&&... args );		(since C++11) (until C++17)
template< class... Args > decltype(auto) emplace( Args&&... args );		(since C++17)

Pushes a new element on top of the stack. The element is constructed in-place, i.e. no copy or move operations are performed. The constructor of the element is called with exactly the same arguments as supplied to the function.

Effectively calls c.emplace_back(std::forward<Args>(args)...);.

Parameters

args

-

arguments to forward to the constructor of the element

Return value

(none)	(until C++17)
The value or reference, if any, returned by the above call to Container::emplace_back.	(since C++17)

Complexity

Identical to the complexity of Container::emplace_back.

Example

Run this code

#include <iostream>
#include <stack>
 
struct S
{
    int id;
 
    S(int i, double d, std::string s) : id{i}
    {
        std::cout << "S::S(" << i << ", " << d << ", \"" << s << "\");\n";
    }
};
 
int main()
{
    std::stack<S> stack;
    const S& s = stack.emplace(42, 3.14, "C++"); // for return value C++17 required
    std::cout << "id = " << s.id << '\n';
}

Output:

S::S(42, 3.14, "C++")
id = 42

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2783	C++17	`emplace` returned `reference`, breaking compatibility with pre-C++17 containers	returns `decltype(auto)`

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Metaprogramming library (C++11)
Diagnostics library
General utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Concurrency support library (C++11)
Execution support library (C++26)
Technical specifications
Symbols index
External libraries

Sequence
array (C++11)
vector
vector<bool>
inplace_vector (C++26)
deque
forward_list (C++11)
list
Associative
set
multiset
map
multimap
Unordered associative
unordered_set (C++11)
unordered_multiset (C++11)
unordered_map (C++11)
unordered_multimap (C++11)
Adaptors
stack
queue
priority_queue
flat_set (C++23)
flat_multiset (C++23)
flat_map (C++23)
flat_multimap (C++23)
Views
span (C++20)
mdspan (C++23)
Tables
Iterator invalidation
Member function table
Non-member function table

Member functions
stack::stack
stack::~stack
stack::operator=
Element access
stack::top
Capacity
stack::empty
stack::size
Modifiers
stack::push
stack::push_range (C++23)
stack::emplace (C++11)
stack::pop
stack::swap (C++11)
Non-member functions
swap(std::stack) (C++11)
operator==operator!=operator<operator>operator<=operator>=operator<=> (C++20)
Helper classes
uses_allocator<std::stack> (C++11)
formatter<std::stack> (C++23)
Deduction guides(C++17)

push	inserts element at the top (public member function)
pop	removes the top element (public member function)