This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: bug in GCC or C++ standard ?
On Tue, Nov 11, 2008 at 6:53 PM, Mark Tall <mtall.qld@gmail.com> wrote:
> Hello,
>
> I've come across an oddity in C++, involving anonymous unions and
> const variables. Neither of the two classes below will compile using
> gcc 4.3.0. Is this a bug in gcc or the C++ standard itself ?
No...
> class my_class_1
> {
> union
> {
> const int x;
> const int y;
> };
>
> my_class_1() : x(0), y(0) {}
> };
>
>
> class my_class_2
> {
> union
> {
> const int x;
> const int y;
> };
>
> my_class_2() : x(0) {}
> };
It's a bug in the code.
In a union only one field can be active at one time, hence
initializing more than one makes no sense ("If a ctor-initializer
specifies more than one mem-initializer for the same member, for the
same base class or for multiple members of the same union (including
members of anonymous unions), the ctor-initializer is ill-formed.")
However, const items need to be initialized, hence potting two in a
union makes no sense.
(The standard doesn't need an explicit rule to say that, as it's
implied by other rules.)
-- James