> > Hi Joakim, > > * Joakim Tjernlund wrote on Mon, Jun 06, 2005 at 04:10:31PM CEST: > > > > I want to use -fpic instead of -fPIC on a powerpc(linux) target since > > that generates smaller and faster libs. But I can't find out how to > > make libtool use -fpic. I don't want to do local changes to the > > installed libtool. build host is linux/x86. > > The setting of pic_flag is hard-wired in AC_LIBTOOL_PROG_COMPILER_PIC in > libtool.m4 now, if that's what you are looking for.
OK, will look at that some more. I don't automake, autoconf and libtool very well so I need a liite guidance here. Can I just run aclocal and modify the generated aclocal.m4? I would then commit aclocal.m4 to CVS and use that when building our libs. Is there a better way? > > But how would you have Libtool find out when it will be used for large > sources for which -fpic will fail? This is mainly for our own development of onboard SW for a embedded target and we want to save space. > (Note I *could* imagine some kind of parametrization a la `-small-pic', > but I'll tell you right away that the amount of possible breakage is > huge, huge, and dangerous, and hard to find only after hours of > compilation; and the resulting fights with users..) hmm, but in some cases it is justified. Think embedded products. > > Two questions to ponder before you think about -fpic: Have you measured > the speed impact of -fpic vs -fPIC? Please show, I'm interested! Nope, but i did look at the libs with readelf -a and found that accesses to a global variables seems to generates a reloc per access to that global variable(why?) and that can quickly waste space. > If the difference is noticeable: Have you slapped the library author > with Drepper's dsohowto.pdf yet? If so, please share with us his/her > reasoning to ignore it. :) Nope, not yet. Will have to slap myself and my team in that case :) I have read that doc and learned a lot from it. However even Drepper seems to like -fpic in one case: glibc for ppc is compiled with -fpic. PPC can handle big libs even with -fpic. > > Regards, > Ralf _______________________________________________ http://lists.gnu.org/mailman/listinfo/libtool