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Re: [PATCH 2/2] replace several uses of the anon namespace with GCC_FINAL
- From: Markus Trippelsdorf <markus at trippelsdorf dot de>
- To: Jeff Law <law at redhat dot com>
- Cc: tbsaunde+gcc at tbsaunde dot org, gcc-patches at gcc dot gnu dot org, richard dot sandiford at arm dot com
- Date: Thu, 13 Aug 2015 01:58:08 +0200
- Subject: Re: [PATCH 2/2] replace several uses of the anon namespace with GCC_FINAL
- Authentication-results: sourceware.org; auth=none
- References: <1439208314-7390-1-git-send-email-tbsaunde+gcc at tbsaunde dot org> <1439208314-7390-2-git-send-email-tbsaunde+gcc at tbsaunde dot org> <55CA4B93 dot 3060003 at redhat dot com> <87oaicbaht dot fsf at e105548-lin dot cambridge dot arm dot com> <55CB9888 dot 4000200 at redhat dot com>
On 2015.08.12 at 13:03 -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
> > 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.
For the record here the gdb bug in question:
https://sourceware.org/bugzilla/show_bug.cgi?id=16874
It even has a patch attached, that improves the issue.
--
Markus