Re: [PATCH 2/2] replace several uses of the anon namespace with GCC_FINAL

[Trevor Saunders <tbsaunde at tbsaunde dot org>]

On Wed, Aug 12, 2015 at 01:03:36PM -0600, Jeff Law wrote:
> On 08/12/2015 12:57 PM, Richard Sandiford wrote:
> >Jeff Law <law@redhat.com> writes:
> >>On 08/10/2015 06:05 AM, tbsaunde+gcc@tbsaunde.org wrote:
> >>>From: Trevor Saunders <tbsaunde+gcc@tbsaunde.org>
> >>>
> >>>Hi,
> >>>
> >>>In many places gcc puts classes in the anon namespace so the compiler can tell
> >>>they do not get inheritted from to enable better devirtualization.  However
> >>>debugging code in the anon namespace can be a pain, and the same thing can be
> >>>accomplished more directly by marking the classes as final.  When
> >>>bootstrapping
> >>>stage 3 should always be built in C++14 mode now, and of course will always be
> >>>newer than gcc 4.7, so these classes will always be marked as final there.
> >>>AIUI cross compilers are supposed to be built with recent gcc, which I would
> >>>tend to think implies newer than 4.7, so they should also be built with these
> >>>classes marked as final.  I believe that means in all important cases
> >>>this works just as well as the anon namespace.
> >>>
> >>>bootstrapped + regtested on x86_64-linux-gnu, ok?
> >>>
> >>>Trev
> >>>
> >>>
> >>>gcc/ChangeLog:
> >>>
> >>>2015-08-10  Trevor Saunders  <tbsaunde@tbsaunde.org>
> >>>
> >>>	* compare-elim.c, dce.c, dse.c, gimple-ssa-isolate-paths.c,
> >>>	gimple-ssa-strength-reduction.c, graphite.c, init-regs.c,
> >>>	ipa-pure-const.c, ipa-visibility.c, ipa.c, mode-switching.c,
> >>>	omp-low.c, reorg.c, sanopt.c, trans-mem.c, tree-eh.c,
> >>>	tree-if-conv.c, tree-ssa-copyrename.c, tree-ssa-dce.c,
> >>>	tree-ssa-dom.c, tree-ssa-dse.c, tree-ssa-forwprop.c,
> >>>	tree-ssa-sink.c, tree-ssanames.c, tree-stdarg.c, tree-tailcall.c,
> >>>	tree-vect-generic.c, tree.c, ubsan.c, var-tracking.c,
> >>>	vtable-verify.c, web.c: Use GCC_FINAL instead of the anonymous
> >>>namespace.
> >>OK.
> >
> >I was hoping someone else was going to speak up since I seem
> >to have been posting a few negative messages recently, but I think
> >this is really a step in the wrong direction.  I think the code
> >was using anonymous namespaces in exactly the way they were

are they actually all that common?  I think gcc is the only C++ with
which I'm familiar that uses them much.

> >intended to be used.
> No need to worry about seeming to be negative.
> 
> 
> The problem is you can't get to stuff in the anonymous namespace easily in
> the debugger.  There was talk of fixing that, but I don't think it ever went
> forward on the gdb side.
> 
> If gdb were to get fixed so that debugging this stuff was easier, then I'd
> fully support putting things back into the anonymous namespace.

I have vague memories of other reasons to dislike the anon namespace
being brought up when it was discussed at $day job, but debuggers was
the big reason (and its not just gdb that's bad)

Trev

> 
> jeff
>