std::stack<T,Container>::swap (3) - Linux Manuals
void swap( stack& other ) noexcept(/* see below */); (since C++11)
Exchanges the contents of the container adaptor with those of other. Effectively calls using std::swap; swap(c, other.c);
other - container adaptor to exchange the contents with
noexcept(noexcept(swap(c, other.c))) (until C++17)
In the expression above, the identifier swap is looked up in the same manner as the one used by the C++17 std::is_nothrow_swappable trait.
noexcept specification: (since C++17)
Same as underlying container (typically constant)
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
LWG_2456 C++11 the noexcept specification is ill-formed made to work
std::swap(std::stack) (function template)