Re: Unreviewed C++0x patches

[Mark Mitchell <mark at codesourcery dot com>]

Jason Merrill wrote:
> Mark Mitchell wrote:
> > If we're not going to fix a long-standing bug in non-0x mode because 
> > it's not a regression -- even though it might affect relatively many 
> > people
>
> I would be inclined to change that policy, too, as long as the patch is 
> deemed safe enough.

I think that's a reasonable point of view, but I think we should decide 
that issue first.  If we stick with the current policy, then making 
changes for C++0x support seems odd.  If we change to a more liberal 
policy, then it makes sense to include fixes for all features (including 
very new ones like C++0x) in that.

> > then fixing C++0x bugs (which presumably affect fewer, given how new 
> > it is), seems wrong.  We're introducing risk for relatively little 
> > upside.
>
> I disagree.  Implementation experience is important to the 
> standardization process; it helps a lot for GCC to be available as a 
> sample implementation of some of the new features.  Though I suppose 
> interested people could grab a snapshot of the trunk sources, that will 
> mean a disconnect between 4.3 usage and eventual standardized usage.

Of course, GCC's mission is not to help with standardization.  By 
actively pushing out pre-standard features we're actually putting our 
users in harm's way; they're likely to end up with code that almost, but 
not quite, matches the standard, and they may then need to change their 
code as we change to match the eventual standard.

I'm all for using GCC to do research on new features and providing input 
back to the committee.  But, that doesn't necessarily have to happen in 
FSF releases; it can happen on branches.

All that said, I'm comfortable with accepting things after they make the 
WP, which has been our informal approach up until now.

> > So, I think the bar ought to be very high.  In particular, I think we 
> > ought to consider this only for silent miscompilation, and only if all 
> > changes are isolated with C++0x conditionals.  And, if we're going to 
> > consider these patches, then I think we ought to consider fixes for 
> > other silent miscompilations as well, even if not regressions.
>
> I think we should consider those regardless of the C++0x issue.  I've 
> expressed before my disagreement with placing higher priority on 
> regressions than on wrong-code bugs.

I think that's the core issue here.  What do others think?

--
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713