Unexpected array when initializing a json const& on gcc 4.8.5 using uniform syntax

[not-a-user]

Minimal example:

#include "json.hpp" // 3.9.1
#include <cassert>
#include <iostream>

using namespace nlohmann;
using namespace std;

int main()
{
        json const j = "{\"key\": null}"_json;
        assert(j.is_object());
        json const& k{j.at("key")};
        cout << k << endl;
        assert(k.is_null());
}

Fails on gcc 4.8.5 with -std=c++0x:

[null]
minimal: minimal.cpp:14: int main(): Assertion `k.is_null()' failed.

Note that k refers to an array, so at() has made a copy though j is const. Don't know if you keep track of that copy via some mutable or if there is a segfault ahead because of a dangling reference.

Passes on more recent gcc.

[nlohmann]

Duplicate of #2311.

[not-a-user]

Duplicate of #2311.

Sure? This affects only older gcc. It really messes badly with the reference initialization.