[Bug c++/67182] New: Initialising map with disabled copy elision yields unexpected results.

[vrgo at wp dot pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67182

            Bug ID: 67182
           Summary: Initialising map with disabled copy elision yields
                    unexpected results.
           Product: gcc
           Version: 5.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vrgo at wp dot pl
  Target Milestone: ---

The below code results in creating a map which contains only a single
(incorrect) key-value pair instead of 3.

Code:

    #include <map>
    #include <iostream>

    struct X
    {
        int x;
        int y;

        bool operator<(const X& other) const { return x < other.x; }
    };

    int main()
    {    
        std::map<X, int> detailsMap = {
            { X{1, 2}, 7 }, 
            { X{3, 4}, 7 },
            { X{5, 6}, 7 }
        };

        std::cout << detailsMap.size() << std::endl;

        auto f = *(detailsMap.begin());

        std::cout << f.first.x << " " << f.first.y << std::endl;
    }


Invocation:

    $ g++ prog.cc -Wall -Wextra -I/usr/local/sprout -std=c++11
-fno-elide-constructors

Output:

    1
    0 0


When I switch off "-fno-elide-constructors" or when I manually add copy and
move constructors to struct X, 'detailsMap' correctly contains 3 given elements
instead of one with some kind of "default" values (X::x = 0 and X::y = 0).

I wasn't able to reproduce this problem with other containers like std::set or
std::vector.

It seems that this behaviour has been introduced in GCC 5.1.0 (I don't have
this problem with GCC 4.9.2). 

I have tried it here: http://melpon.org/wandbox/permlink/El3p1eAcZ3azCsFi