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Mike Frysinger wrote the following on 30.09.2006 23:48 : |
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> [...] |
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> `man gcc` always seemed fine to me |
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> |
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> in fact, lets read the -ffast-math section: |
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> -ffast-math |
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> This option should never be turned on by any -O option since it can |
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> result in incorrect output for programs which depend on an exact |
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> implementation of IEEE or ISO rules/specifications for math func- |
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> tions. |
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> |
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> this flag is never safe to use in CFLAGS |
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> |
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> |
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|
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Indeed, I'll add a reminder to adventurous users to check `man gcc` (I |
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believe I added fast-math following an example somewhere on the web |
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instead of checking the man page). |
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|
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>> link='http://gentoo-wiki.com/CFLAGS_matrix' |
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>> |
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> |
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> no way will our documentation link to gentoo-wiki.com |
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> |
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> |
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|
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The GWN paragraph is mainly a 'heads-up' kind of thing, no more. Don't |
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confuse the GuideXML extract with an official documentation extract, GWN |
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uses GuideXML too :-) |
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|
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>> If possible, I'd like to expand the list of 3.4.6 -> 4.1.1 upgrade |
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>> problems which are linked to experimental CFLAGS |
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>> |
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> |
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> i find maintaining a list of "safe" CFLAGS on a per-gcc basis to be a waste of |
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> time ... but that's just me |
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> |
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|
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That's not the idea. The main idea is to remind people that playing with |
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CFLAGS is allowed, as long as you remember to revert to safe CFLAGS |
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before reporting bugs. |
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As I wasted one dev time by forgetting to check my CFLAGS, I merely |
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thought that maybe this wasn't a common reflex for other users too |
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(fast-math was the only unsafe flag I used, I'm pretty conservative and |
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simply was mistaken because roughly 2 years ago I didn't check the |
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proper source of information: the man page). Maybe very few bug reports |
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are caused by inadequate CFLAGS. If my problem is an uncommon exception |
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I won't press the matter further, there would be no point to do so. |
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|
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I'll wait and see if other devs are aware of common CFLAGS gotchas |
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plaguing bugzilla. |
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|
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Lionel. |
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-- |
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