140918 2006-07-18 07:29 0000 bzflag weird behavior with -fstrict-aliasing 2006-12-22 14:21:12 0000 1 1 1 Unclassified Gentoo Linux Games unspecified All Linux RESOLVED FIXED P2 normal --- 1 andreas@tpwch.com games@gentoo.org morrison@brlcad.org andreas@tpwch.com 2006-07-18 07:29:33 0000 I've been having some problems with bzflag lately, that is that if I shoot someone I won't hit them, and the other persons doesn't see my shots. After googling around a bit I found this upstream bug posted over a year ago, but nothing has happened after that, so the devs must have missed it: http://sourceforge.net/tracker/index.php?func=detail&aid=1191085&group_id=3248&atid=103248 The person who reported that says that it will get this weird behavior with gcc 4.0 and -O2 or -fstrict-aliasing. I have found that it also happens with -O3. And sure enough, downgrading the cflags to -O1 fixed the problem. If the bug is caused by >=-O2 implying -fstrict-aliasing then the most correct workaround would be to add -fno-strict-aliasing, otherwise I guess you'll have to filter out -O2 -O3 and -Os. I have posted a comment in the upstream bug, and hopefully it'll get some attention from the upstream developers so they can provide a proper fix My emerge info: Portage 2.1.1_pre3-r1 (default-linux/amd64/2006.0, gcc-4.1.1/amd64-vanilla, glibc-2.4-r3, 2.6.17-gentoo-r2-tpc1 x86_64) ================================================================= System uname: 2.6.17-gentoo-r2-tpc1 x86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 4400+ Gentoo Base System version 1.12.1 ccache version 2.4 [enabled] app-admin/eselect-compiler: 2.0.0_rc2-r1 dev-lang/python: 2.4.3-r1 dev-python/pycrypto: 2.0.1-r5 dev-util/ccache: 2.4-r2 dev-util/confcache: [Not Present] sys-apps/sandbox: 1.2.18.1 sys-devel/autoconf: 2.13, 2.60 sys-devel/automake: 1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r2 sys-devel/binutils: 2.17 sys-devel/gcc-config: 2.0.0_rc1 sys-devel/libtool: 1.5.22 virtual/os-headers: 2.6.16 ACCEPT_KEYWORDS="amd64 ~amd64" AUTOCLEAN="yes" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-march=athlon64 -mtune=athlon64 -msse3 -O3 -pipe" CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /usr/share/X11/xkb" CONFIG_PROTECT_MASK="/etc/env.d /etc/env.d/java/ /etc/eselect/compiler /etc/gconf /etc/java-config/vms/ /etc/revdep-rebuild /etc/terminfo" CXXFLAGS="-march=athlon64 -mtune=athlon64 -msse3 -O3 -pipe" DISTDIR="/usr/portage/distfiles" FEATURES="autoconfig ccache confcache distlocks fixpackages metadata-transfer parallel-fetch sandbox sfperms strict" GENTOO_MIRRORS="http://ds.thn.htu.se/linux/gentoo http://ftp.du.se/pub/os/gentoo http://distfiles.gentoo.org http://www.ibiblio.org/pub/Linux/distributions/gentoo" LANG="sv_SE.ISO-8859-1" LC_ALL="sv_SE.ISO-8859-1" LINGUAS="sv" MAKEOPTS="-j3" PKGDIR="/usr/portage/packages" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --delete-after --stats --timeout=180 --exclude='/distfiles' --exclude='/local' --exclude='/pac kages'" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/usr/portage" PORTDIR_OVERLAY="/usr/local/portage" SYNC="rsync://rsync.europe.gentoo.org/gentoo-portage" USE="amd64 GAPING_SECURITY_HOLE X a52 aac aalib acpi alsa amr ao apache apache2 ares asf authfile avi bash-completion bcmath berkdb bluetooth browserplugin bzip2 cairo cddb cdparanoia cli crypt cups curl curlwrappers custom-cflags dbus dga dlloader dmi dri dv dvd dvdread encode faad fam ffmpeg flac fontconfig foomaticdb fortran ftp gd gdbm gif gimp glibc-omitfp glitz gnutls gphoto2 gs gtk gtk2 hal hub idn imagemagick inkjar iontruetype ithreads java javascript jce jpeg kqemu latin1 lcms libcaca libg++ live logitech-mouse logrotate lua mad mikmod mmap mng modplug mp3 mp4 mpeg musepack musicbrainz mysql ncu rses nls noflagstrip nptl nptlonly nsplugin nvidia offensive ogg opengl opensslcrypt pam panel-plugin parse-clocks pcre pda pdf pdflib perl pg-intdatetime php png pwdb python quicktime rdesktop readline r ewrite rtc ruby sasl scanner sdl session shaper simplexml slang smp sockets speex spell sql ssl subversion svg symlink syslog theora threads thumbnail thunar-vfs tiff timidity truetype truetype-fonts type 1-fonts udev usb vcd vchroot vim-pager vim-with-x vorbis vroot wxwindows x264 xanim xcomposite xml xml2 xorg xpm xv xvid xvmc zip zlib elibc_glibc input_devices_keyboard input_devices_mouse kernel_linux l inguas_sv userland_GNU video_cards_nv video_cards_nvidia" Unset: CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LDFLAGS, PORTAGE_RSYNC_EXTRA_OPTS andreas@tpwch.com 2006-07-18 07:40:48 0000 *** Bug 140919 has been marked as a duplicate of this bug. *** vapier@gentoo.org 2006-07-19 19:00:58 0000 bzflag itself should fix its code or force -fno-strict-aliasing in their build system in the meantime, an 'append-flags -fno-strict-aliasing' in the ebuild should be ok morrison@brlcad.org 2006-10-27 13:37:22 0000 This is a relatively recently introduced issue related to IEEE floating point operations going on in the code that haven't yet been isolated. I believe that if you add -mieee or a similar IEEE compliance option that you can then proceed to use any -O# optimization level desired. one of the bzflag devs morrison@brlcad.org 2006-10-27 13:54:02 0000 It's also probably worth mentioning that there was a separate issue in the networking protocol that affected (only some) 64-bit platforms that caused similar inabilities to shoot other players that has been fixed in the latest CVS sources but not yet pushed out via a public release. The next public release isn't scheduled until around the end of the calendar year. If, however, someone (tm) can work with the user experiencing this problem to determine if it's the ieee or 64-bit issue and it's issue that folks would like to see fixed earlier rather than later, then a patch could probably be put together. Otherwise, both of the issues should be fixed for the next release. Cheers! Sean vapier@gentoo.org 2006-10-27 22:46:09 0000 i doubt it considering -mieee is an alpha/superh specific flag the original comment is most likely correct ... bzflag uses casting that violates ISO spec for aliasing and now that gcc-4 enables strict-aliasing by default with -O2, people are noticing tupone@gentoo.org 2006-12-22 14:21:12 0000 A fix is now in portage. Thanks for report