On Wed, Apr 01, 2015 at 07:45:10AM +0000, Kavanagh, Mark B wrote: > > >On Tue, Mar 31, 2015 at 11:23:32PM +0100, Mark Kavanagh wrote: > >> DPDK 2.0 contains an updated implementation of rte_memcopy, which > >> leverages SSE and AVX instrinsics. In versions of GCC <= 4.8.2, it > >> has been observed that the relevant instrinsics are not defined in > >> gcc headers, resulting in compile-time errors. > >> This issue is resolved by enabling the 'mssse3' flag at compile time; > >> however, it's not possible to pass an additional flag via the command > >> line without overwriting an existing compiler variable. > >> > >> Introduce an additonal configuration option to resolve this. > >> > >> Signed-off-by: Mark Kavanagh <mark.b.kavan...@intel.com> > > > >What's wrong with setting CFLAGS on the "configure" or "make" command > >line? This is the standard way to do this with Automake and Autoconf. > > Sure. However, setting CFLAGS on the command line overwrites any > values CFLAGS has attained via the 'configure' step. The most obvious > symptom of this is significantly degraded performance, due to the fact > that the optimization flags passed to CFLAGS during 'configure' are > overwritten by the command line value of CFLAGS.
CFLAGS only has "-O2 -g" by default, which is the same in every Autoconf setup. You can supply those yourself. > >We should certainly not introduce a configure option for every single > >possible compiler flag. > > Agreed; given the precedent set by OVS_ENABLE_WERROR, I figured that > this was the convention. -Werror is a special case because it must not be enabled during "configure" but only for the build. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
