[Bug c++/70932] flexible array member with non-trivial destructor

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70932

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2016-05-04
      Known to work|                            |4.9.3, 5.3.0
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot 
gnu.org
     Ever confirmed|0                           |1
      Known to fail|                            |6.1.0

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
The problem was introduced r233126 as a result of switching the internal
flexible array representation to use a null type domain.  Prior to 6.1, GCC
treated flexible array members the same as arrays of zero elements.

I'll have to think about what the right solution is: reject flexible array
members with non-trivial destructors with a better error (like clang does) or
allow them with a warning.  My concern with allowing them is that while G++ 6.1
allows them to be initialized (5.x rejects the initialization which seems like
a bug), it won't be able to invoke their destructor in code like this:

  struct A {
    int i;
    ~A() { __builtin_printf ("%s\n", __PRETTY_FUNCTION__); }
  };

  struct S {
    int i;
    A a[];
  };

  int main ()
  {
    S s = { 3, { 1, 2, 3 } };
  }