[Bug c++/57758] New: gcc accepts incorrect in-class brace initializers

[lundberj at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57758

            Bug ID: 57758
           Summary: gcc accepts incorrect in-class brace initializers
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lundberj at gmail dot com

In summary, having a class member in-class copy-construct from itself (!)
compiles without warning when curly-brace syntax is used.

The result is that the class invariants are never established. The following
code is accepted: 

#include <iostream>
struct C{
   C()=delete;
   C(const C& other): x(other.x+1){}
   int x=10;
};
struct D{
   C c0{c0};  // << -- compiles without warning
 //C c1{c1};  // << -- correctly rejected
};
int main(){
   D d;
   std::cout << d.c0.x << std::endl; // prints 1
}

You already get the point. Similarly, these definitions of C also compiles, and
the printed value of x is 0 in both cases.

struct C{
   int x=10;  
   C(float,float){}
};
struct C{
   int x=10;  
};

Using the following definition I get an un-initialized reference: x == 1412476
:

struct C{
   C(const C& other): z(other.z),x(other.x){}
   int z=10;
   int & x{z};
};

This seems like something that would be good to detect.

Using class C{}; is correctly rejected (with 'too many initializers for ‘C’').