On Mon, 2014-12-22 at 15:33 -0600, Chaoran Yang wrote: > Hi all, > > I’m trying to use the __attribute__((optimize(“-O2”))) to mark a > function that should always be optimized. But it doesn’t seem to work. > I’ve tested both GCC 4.9.2 and 4.8.3, they both silently ignored the > attribute. I’m wondering if I’m something super stupid that I’m not > aware of. Try __attribute__((optimize("O2")) i.e. remove the leading '-'. See also: https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function-Attributes "Strings that begin with O are assumed to be an optimization option, while other options are assumed to be used with a -f prefix. " Cheers, Oleg