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Re: using non-standard optflags (-O3, in particular)



Ralf Corsepius wrote:
On Fri, 2007-02-09 at 10:59 -0500, Simon Perreault wrote:
Ralf Corsepius wrote:
So, the only results of recommendations to trust when it comes to
packaging binaries for a distro is those who are deeply familiar with
the guts of the OS, in case of Fedora, RH's GCC, glibc and kernel
developers.
This is BS.
Beg your pardon?

You don't need that level of familiarity to make good recommendations. You make it sound like Red Hat has some kind of old wise man and only he knows enough, and he only speaks once a year on summer solstice.

Sure, people have thought about the defaults, but it doesn't mean that the packager doesn't know what he's doing either.
Rest assured: In 99% of all cases they don't know.

Ok now, you say 99% of packagers can't package? BS.

They test on their "Pentium IV" and claim something - They can't have
any clues about what happens on a sparc, an i586 and AMD X2 <what the heck>, or a ppc something.

You sound very condescending.

Some software, particularly numerical computation stuff, is built for being optimized properly. There are some extreme cases where using -O2 instead of -O3 simply makes a piece of software useless (take Blitz++ for example).
In other words: Crappy non-portable SW,

The particular example I gave is a marvel of software engineering, useful to many scientists working with big arrays.

What about ATLAS? It's currently in Extras, and the packager has done many unorthodox things to ensure maximum efficiency. Compiling it with -O2 would be stupid.

It is - It renders debugging impossible on many systems,

Not much worse than -O2 already is.

strict-aliasing
silently kills SW on some targets

You know this is enabled at -O2 right?

it might trigger exotic
target-specific bugs etc. etc.

BS, and you know it.

As part of the distro you can't to compromise between different
trade-offs.

WTF? You think Fedora isn't about compromise? It's full of it! People here compromise every single day. And that's a good thing! People who don't want the compromise a distro imposes on them run Linux from Scratch.


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