Description of problem:

What problem/issue/behavior are you having trouble with?  What do you expect to see?

I am using dev toolset 6.0. Here is a small reproduction: 
//a.C
#include <string>
#include <iostream>

class Trouble {
  public:
    explicit Trouble(int) { std::cout << "int" << std::endl; }

    Trouble(const char *) { std::cout << "const char*" << std::endl; }
    // Trouble(const signed char *) {}
    Trouble(const unsigned char *) { std::cout << "const unsigned char* " << std::endl;}

  private:
    std::string data;
};

Trouble makeTroubleObject() { return Trouble(42); }
Trouble makeTrouble() { return 42; }

int main()
{
  auto o1 = makeTroubleObject();
  auto o2 = makeTrouble();

  return 0;
}

Build it with
g++ -std=c+=14 -g a.C

I expect I should get a compilation error in this line as the constructor is explicit. 

"Trouble makeTrouble() { return 42; }"

But it compiles fine, and even worse, it seems the object "o2" was not constructed properly thus I got a core dump.


This affects our adoption of Dev toolset 6.0.


Version-Release number of selected component (if applicable):

gcc version 6.2.1 20160916 (Red Hat 6.2.1-3) (GCC) 


How reproducible:

Always

Steps to Reproduce:
1. compile test program
2. execute compiled test
3. boom.

Actual results:

<snip>
[fmhirtz@ivanova ~]$ g++ --std=c++14 -g a.C -g
[fmhirtz@ivanova ~]$ ./a.out 
int
Segmentation fault (core dumped)
</snip>

Expected results:

Compilation failure likely.

Additional info:

This is impacting the client's ability to migrate to DTS6 so it's a priority.