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Re: GCC-4.5.2 Has Serious Problems
 

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1i5t5.duncan at cox

Jun 30, 2011, 7:18 PM


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Re: GCC-4.5.2 Has Serious Problems [In reply to]

Frank Peters posted on Thu, 30 Jun 2011 21:04:29 -0400 as excerpted:

> On Fri, 01 Jul 2011 02:44:36 +0300 Nikos Chantziaras <realnc [at] arcor>
> wrote:
>
>> And here you can read more thorough information about strict aliasing:
>>
>> http://labs.qt.nokia.com/2011/06/10/type-punning-and-strict-aliasing
>>
> You've saved the day in more ways than one.
>
> A few days ago I posted about a possible problem with a floating point
> test called the UCBTEST. After examining the source code of this test,
> I see violations of aliasing rules throughout. It's hard to efficiently
> manipulate variables without them.
>
> Of course, this code was written before the C99 standard and so is
> exempt. But the use of "-fno-strict-aliasing" will apply with the
> UCBTEST as well.

Truthfully, I thought sure this was a direct follow-on to that! So I'm
happy to see that the same cause and solutions apply. =:^)

As I said in an earlier post, tho, expect there to be more problems like
that with code of that age as time goes on, because they're well past the
easy optimizations now, and into stuff like this. So it may be wise to
keep an eye out and test the minor gcc version bumps with an eye toward
such issues. They generally put out a porting guide, etc, with the new
version, that you can read for clues in case the tests start doing
unexpected things again.

(If you pay attention to flameeyes' blog, he tends to cover such things
reasonably early on after release of a new gcc version as well, as he
does tinderbox runs to see how bad the interaction of the new version is
with the current gentoo ~arch tree as a whole and eventually to test that
the latest ~arch packages are updated or patched to fix the problem,
before that gcc version gets unmasked to ~arch. By no means do I agree
with everything he says, but he really is an asset to gentoo and would be
sorely missed should one of his sick episodes make it impossible for him
to continue, or if he simply decided he had better things to do with his
time. The switch to --as-needed in Gentoo's default ldflags was largely
due to his work, explaining the issues for other devs, testing and filing
bugs, helping with the hard cases, and in general pushing it until it
happened, for instance, and every single gentoo user benefits from that
in the form of less mandatory rebuilds, every time they update. It may
well have happened without him, but it might have taken a decade longer,
too. And because gentoo devs normally push those patches upstream where
they can, that has been a benefit to the entire FLOSS community, not just
gentoo, as well, reducing "dependency hell" for everyone.)

--
Duncan - List replies preferred. No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master." Richard Stallman

Subject User Time
GCC-4.5.2 Has Serious Problems frank.peters at comcast Jun 30, 2011, 2:45 PM
    Re: GCC-4.5.2 Has Serious Problems wonko at wonkology Jun 30, 2011, 3:30 PM
        Re: GCC-4.5.2 Has Serious Problems frank.peters at comcast Jun 30, 2011, 4:34 PM
        Re: Re: GCC-4.5.2 Has Serious Problems ianmcc at physik Jun 30, 2011, 7:30 PM
    Re: GCC-4.5.2 Has Serious Problems realnc at arcor Jun 30, 2011, 4:35 PM
        Re: GCC-4.5.2 Has Serious Problems realnc at arcor Jun 30, 2011, 4:44 PM
            Re: Re: GCC-4.5.2 Has Serious Problems frank.peters at comcast Jun 30, 2011, 5:04 PM
                Re: GCC-4.5.2 Has Serious Problems realnc at arcor Jun 30, 2011, 5:11 PM
                    Re: GCC-4.5.2 Has Serious Problems 1i5t5.duncan at cox Jun 30, 2011, 5:58 PM
                        Re: Re: GCC-4.5.2 Has Serious Problems frank.peters at comcast Jun 30, 2011, 6:23 PM
                            Re: GCC-4.5.2 Has Serious Problems 1i5t5.duncan at cox Jun 30, 2011, 6:52 PM
                            Re: Re: GCC-4.5.2 Has Serious Problems ianmcc at physics Jun 30, 2011, 7:15 PM
                            Re: Re: GCC-4.5.2 Has Serious Problems markknecht at gmail Jun 30, 2011, 9:36 PM
                                Re: Re: GCC-4.5.2 Has Serious Problems frank.peters at comcast Jun 30, 2011, 10:22 PM
            Re: Re: GCC-4.5.2 Has Serious Problems frank.peters at comcast Jun 30, 2011, 5:25 PM
            Re: Re: GCC-4.5.2 Has Serious Problems frank.peters at comcast Jun 30, 2011, 6:04 PM
                Re: GCC-4.5.2 Has Serious Problems 1i5t5.duncan at cox Jun 30, 2011, 7:18 PM
                Re: Re: GCC-4.5.2 Has Serious Problems chemoelectric at chemoelectric Jun 30, 2011, 7:22 PM
                    Re: Re: GCC-4.5.2 Has Serious Problems frank.peters at comcast Jun 30, 2011, 7:43 PM
                Re: GCC-4.5.2 Has Serious Problems realnc at arcor Jul 1, 2011, 4:53 AM
                    Re: Re: GCC-4.5.2 Has Serious Problems frank.peters at comcast Jul 1, 2011, 9:53 AM

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