[Bug c++/79307] New: g++ misses warning for reference on temporary that invokes undefined behaviour

[steven.spark at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79307

            Bug ID: 79307
           Summary: g++ misses warning for reference on temporary that
                    invokes undefined behaviour
           Product: gcc
           Version: 5.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: steven.spark at gmail dot com
  Target Milestone: ---

I thought (something like) this was fixed in bug 986

Code:
struct TestRefInt {
    TestRefInt(const int& a) : a_(a) {};
    void DoSomething() {    cout << "int:" << a_ << endl;  }
protected:
    const int& a_;
};

TestRefInt tfi(55);

int main() {
    TestRefInt ltfi(8);

    tfi.DoSomething();
    ltfi.DoSomething();
    return 0;
}

The first one does not work, the second one happens to work (but only by
"accident"). 

Similar issue:

struct TestRefIntDirect {
    TestRefIntDirect(int a) : a_(a) {};
    void DoSomething() {    cout << "int:" << a_ << endl;  }
protected:
    const int& a_;
};

Lifetime of the temporary is not extended in neither case (as per C++11
standard 12.2 p5).

Tested with MinGW 5.3.0, avr-g++ 4.8.1, 4.9.2.

I would like if warning were produced for these. Any help would be appreciated.

I posted more details on stack overflow
http://stackoverflow.com/questions/41928634/c11-scoping-and-lifetime-of-temporary-bound-to-a-const-reference-gcc

Possible duplicate of bug #44859 or bug #51270.