Re: [gentoo-user] Re: Upgrading gcc: both 4.4 and 4.5 needed?

[Pandu Poluan]

On Nov 18, 2011 9:27 PM, "Willie Wong" <wwong@××××××××××××××.edu> wrote:
>
> On Thu, Nov 17, 2011 at 07:41:21PM +0000, James wrote:
> > > Now, why can't the USE descriptions be like the kernel option
> > > descriptions and have something like what Pandu wrote included?
> >
> > I added this to root's  .bashrc a long time ago:
> >
> > # USE flag settings hack by Ciaran McCreesh:
> > explainuseflag(){ sed -ne "s,^\([^ ]*:\)\?$1 - ,,p" $(portageq
> > portdir)/profiles/use.{,local.}desc; }
> > alias ef="explainuseflag"
> >
> >
> > Then simply use the alias for a quick check to learn about all the
different
> > uses of a given flag:
> >
> > 'ef graphite'
> >
> > # ef graphite
> > Enable support for non-Roman fonts via media-gfx/graphite2
> > Enable support for non-Roman fonts via media-gfx/graphite2
> > Add support for the framework for loop optimizations based on a
polyhedral
> > intermediate representation
> >
> > Then drill down into the a specific package's use flag meaning, using
the
> > aforementioned 'equery u' delineated by Albert.
>
> You people seem to miss my point. I know perfectly well how to find
> the USE descriptions. It is just that the USE description, in this
> case (as in many others) isn't terribly useful.
>
> "Add support for the framework for loop optimizations based on a
> polyhedral intermediate representation" means absolutely gibberish to
> me.
>
> But if one were to add an additional one or two lines a la Pandu,
> about how it is supposed to make " gcc-4.5.3 use a newer method to
> detect parallelism, thus (potentially) makes programs compiled by gcc
> to have better multithreaded performance" and perhaps even a Kernel
> help page style "It is mostly stable. If unsure, say Yes."
>
> It would be ever so much more helpful for people who would like to
> find out what new flags do before deciding whether or not to follow
> the default recommended by the devs which are set into the profile.
>
> (I'm not saying this type of hand holding is necessary for all flags:
> "enable support for non-Roman fonts via media-gfx/graphite2" is
> perfectly understandable, as are most other flags about features a
> "user" is likely to interact with. But for some of the more "system"
> type flags (see also that python/perl flag business from the recent
> months), I think the USE descriptions can stand some improvement.)
>

I agree with you (and not because my name is mentioned :-P).

I got lucky with USE "graphite": gcc's homepage is quite clear; a 15-minute
reading convinced me to try graphite. But there are still lots of other USE
flags that sent me on hours of goose-chase before I can enable/disable with
conviction.

I'm not sure where to put the more detailed explanations, though; perhaps a
$PN.usedesc file in the package's directory? Kind of a complement to the
.ebuild file(s).

Rgds,