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