On Tue, Nov 04, 2003 at 04:20:41PM +0800, Zhang Weiwu wrote: > Hello. I'm running 5.1-RELEASE. > > I read the gcc man page. It is not clear what -O implys. Is -O equal to > -O1 or -O2? If I wish to optimize making does it make sense to add > CFLAGS=-O2 in the make.conf(5)?
-O is the same as -O1 Ah -- the shibboleth of cranking up the optimisation level to make things run *really fast*. First of all, for general purpose code, -O gets you most of the available optimisation benefits without causing any problems. You can try CFLAGS=-O2 in /etc/make.conf if you like, and most things will work OK but by no means all: some code will not compile correctly under high optimization levels. The immediate response if you report this sort of thing as a bug will be to see if the problem is repeatable using a lower optimisation level. Secondly, you will achieve a much greater performance improvement by setting the CPUTYPE variable appropriately. Cheers, Matthew -- Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks Savill Way PGP: http://www.infracaninophile.co.uk/pgpkey Marlow Tel: +44 1628 476614 Bucks., SL7 1TH UK
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