On Sat, Apr 17, 2010 at 3:48 AM, Emmanuel Benisty <benisty.e@xxxxxxxxx> wrote: > Thanks for your reply Allan. > > On Sat, Apr 17, 2010 at 5:30 AM, Allan McRae <allan@xxxxxxxxxxxxx> wrote: >> On 17/04/10 00:03, Emmanuel Benisty wrote: >>> >>> Just out of curiosity, what is the plan regarding this issue (quoted >>> from the gcc changelog): >>> >>> On x86 targets, code containing floating-point calculations may run >>> significantly slower when compiled with GCC 4.5 in strict C99 >>> conformance mode than they did with earlier GCC versions. This is due >>> to stricter standard conformance of the compiler and can be avoided by >>> using the option -fexcess-precision=fast; >>> >> >> From what I understand, this requires passing -std=c99 (or equivalent) to >> the compiler for it to use strict C99 mode. So most software will not be >> affected. Of course, the maintainer of any software the does set C99 mode >> should consider this. > > If it does affect only that type of code and if you recommend the > maintainers to use this option in those cases then wouldn't it simpler > to add it to /etc/makepkg.conf by default and thus make it a > no-brainer for maintainers? > What's wrong with stricter standard conformance ? That sounds like a good change. How can you tell that these apps with floating-point calculations were not actually buggy with previous versions of gcc (or with -fexcess-precision=fast now) ? It does not seem a very good idea to set that globally. I think that should be done case per case, and not by maintainers, but by the developers of the apps, who know well their code, and can make a reasonable decision whether they want/need performance or conformance/accuracy. And you *need* to know how these two aspects are affected if you want to make a reasoned and informed change, rather than a blind and clueless one.
