c++ - Getting a unique_ptr out of a priority queue -

i maintaining set of unique_ptr instances in priority_queue. @ point, want first element , remove queue. however, produces compiler error. see sample code below.

int main () {   std::priority_queue<std::unique_ptr<int>> queue;   queue.push(std::unique_ptr<int>(new int(42)));    std::unique_ptr<int> myint = std::move(queue.top());   return 1; } 

this produces following compiler error (gcc 4.8.0):

uptrtest.cpp: in function ‘int main()’: uptrtest.cpp:6:53: error: use of deleted function ‘std::unique_ptr<_tp, _dp>::unique_ptr(const std::unique_ptr<_tp, _dp>&) [with _tp = int; _dp = std::default_delete<int>]’    std::unique_ptr<int> myint = std::move(queue.top());                                                      ^ in file included /usr/include/c++/4.8/memory:81:0,                  uptrtest.cpp:1: /usr/include/c++/4.8/bits/unique_ptr.h:273:7: error: declared here        unique_ptr(const unique_ptr&) = delete;        ^ 

changing code use queue in this question fixes issue , code compiles fine.

is there no way keep unique_ptrs in priority_queue or missing something?

std::priority_queue::top() returns const reference can't move it. looking @ public interface of priority_queue there no method non-const reference can move (which mandatory unique_ptr, has no copy constructor).

solution: replace unique_ptr shared_ptr able copy them (and not move them).

or, of course, use kind of container altogether (but if chose priority_queue in first place, not acceptable you).

you maybe use "protected member hack" access protected member c (the underlying container) wouldn't recommend it, quite dirty , quite ub.