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From: David Brown on 25 May 2010 16:25
Albert van der Horst wrote:
> In article <4BFBC92D.9019CE15(a)bytecraft.com>,
> Walter Banks <walter(a)bytecraft.com> wrote:
> <SNIP>
>> The paper touches on source code ways to improve the quality
>> of source level debugging information. Source level debugging is
>> important but in many fundamental ways this is one of the major
>> aggravating factors in gcc. One of the fundamental ways to ship
>> reliable code is to ship the code that was debugged and tested.
>> Code motion and other simple optimizations leaves GCC's
>> source level debug information significantly broken forcing
>> many developers to debug applications with much of the
>> optimization off then recompile later with optimization on but
>> the code largely untested.
>
> Tanenbaum once said in a lecture:
> " Global optimisers and symbolic debuggers are each others
> arch enemies"
> A moment of thought should be enough to convince one self of
> the truth of this.
>
> I fail to see how this situation is different for GCC than for
> any compiler.
>
> By the way.
> - The very best code is tested but never debugged,
> because there is no need.
> (Chuck Moore the inventor of Forth reportedly never debugs.
> He checks his code and it works. Mostly subprograms are one line.
> That makes it easier, of course. )
> - I always run tests on shipped code. Don't you?
> - If you expect the outcomes of different optimisation levels
> to be different, you're living a dangerous live, because
> apparently you don't trust your code not to have undefined behaviour.
>

I agree on all of the above.

A few more relevant quotations:

Knuth: "Beware of bugs in the above code; I have only proved it correct,
not tried it".

(I can't remember who said the following - I think it was either K or R
of K&R C fame.)
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are, by
definition, not smart enough to debug it."
From: 42Bastian Schick on 26 May 2010 02:04
On Tue, 25 May 2010 14:24:00 +0000 (UTC), Grant Edwards
<invalid(a)invalid.invalid> wrote:

>>
>> http://www.linux-kongress.org/2009/slides/compiler_survey_felix_von_leitner.pdf
>>
>> It's an interesting paper in several ways
>
>Is the paper available somewhere?

I entered the URL in firefox and got it. What is your problem ?

--
42Bastian
Do not email to bastian42(a)yahoo.com, it's a spam-only account :-)
Use <same-name>@monlynx.de instead !
From: 42Bastian Schick on 26 May 2010 02:09
On Tue, 25 May 2010 08:57:17 -0400, Walter Banks
<walter(a)bytecraft.com> wrote:


>Code motion and other simple optimizations leaves GCC's
>source level debug information significantly broken forcing
>many developers to debug applications with much of the
>optimization off then recompile later with optimization on but
>the code largely untested.

I see not, why "broken debug information" is an excuse for not testing
the final version. In an ideal world, there should be no need to debug
the final version ;-)

And if optimization breaks your code, it is likely your code was
broken before ( e.g. missing 'volatile').


--
42Bastian
Do not email to bastian42(a)yahoo.com, it's a spam-only account :-)
Use <same-name>@monlynx.de instead !
From: David Brown on 26 May 2010 02:52
On 26/05/2010 08:04, 42Bastian Schick wrote:
> On Tue, 25 May 2010 14:24:00 +0000 (UTC), Grant Edwards
> <invalid(a)invalid.invalid> wrote:
>
>>>
>>> http://www.linux-kongress.org/2009/slides/compiler_survey_felix_von_leitner.pdf
>>>
>>> It's an interesting paper in several ways
>>
>> Is the paper available somewhere?
>
> I entered the URL in firefox and got it. What is your problem ?
>

I suspect he was hoping to find a full text paper, with the transcript
of the talk, rather than just the slides.

From: Grant Edwards on 26 May 2010 10:15
On 2010-05-26, 42Bastian Schick <bastian42(a)yahoo.com> wrote:
> On Tue, 25 May 2010 14:24:00 +0000 (UTC), Grant Edwards
><invalid(a)invalid.invalid> wrote:
>
>>>
>>> http://www.linux-kongress.org/2009/slides/compiler_survey_felix_von_leitner.pdf
>>>
>>> It's an interesting paper in several ways
>>
>>Is the paper available somewhere?
>
> I entered the URL in firefox and got it. What is your problem ?

I didn't find a paper. All I could find were "powerpoint" slides.

--
Grant Edwards grant.b.edwards Yow! Bo Derek ruined
at my life!
gmail.com
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