[Bug c++/54258] New: Wrong size of a named union.

[Bug c++/54258] New: Wrong size of a named union.

[karolmdv at gazeta dot pl]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54258

             Bug #: 54258
           Summary: Wrong size of a named union.
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: karolmdv@gazeta.pl


Created attachment 28014
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28014
Compiler's output.

I tried to find it in the current list of open bugs and have seen many similar
union-specific ones.

The problem was detected when using std::aligned_storage, when noticed that
sizeof(std::aligned_storage<x>) yields 1 for any "x".

The following code demonstrates the problem.

----------------------------------------------------------------

int main()
{
    // If "type" is removed (making the union anonymous),
    // it works and returns 18.
    struct my_aligned_storage
    {
        union type
        {
            unsigned char __data[18];
        };
    };
    return sizeof(my_aligned_storage); // Returns 1.
}

----------------------------------------------------------------

It has been compiled with (GCC 4.7.0):

g++ -v -save-temps -o bug.exe -std=gnu++11 bug.cpp

Full compiler's output is in the attachment.

[Bug c++/54258] Wrong size of a named union.

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54258

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-08-14 16:38:32 UTC ---
my_aligned_storage is an empty type, i.e. has no members, so has size 1.

my_aligned_storage::type is not a member, it's a declaration of a type.

If you remove the name 'type' then the anon union is a member, not a type
declaration.