The new xorg (currently masked for testing) segfaults almost constantly when compiled with gcc 3.4.1 and CFLAGS="-O2 -march=pentium4". This problem goes away if -march is backed down to pentium3. The problem seems to be specific to gcc 3.4; I was able to compile/run with "-O2 -march=pentium4" on 3.3.4 with no problems. For completeness' sake, here is my emerge --info: Portage 2.0.50-r10 (2.6, gcc-3.4.1, glibc-2.3.4.20040808-r0, 2.6.8.1-mm3) ================================================================= System uname: 2.6.8.1-mm3 i686 Mobile Intel(R) Pentium(R) 4 - M CPU 2.00GHz Gentoo Base System version 1.5.3 distcc 2.17 i686-pc-linux-gnu (protocols 1 and 2) (default port 3632) [enabled] Autoconf: sys-devel/autoconf-2.59-r4 Automake: sys-devel/automake-1.8.5-r1 ACCEPT_KEYWORDS="x86 ~x86" AUTOCLEAN="yes" CFLAGS="-O2 -march=pentium3 -mtune=pentium3" CHOST="i686-pc-linux-gnu" COMPILER="" CONFIG_PROTECT="/etc /usr/X11R6/lib/X11/xkb /usr/kde/2/share/config /usr/kde/3/share/config /usr/share/config /usr/share/texmf/dvipdfm/config/ /usr/share/texmf/dvips/config/ /usr/share/texmf/tex/generic/config/ /usr/share/texmf/tex/platex/config/ /usr/share/texmf/xdvi/ /var/qmail/control" CONFIG_PROTECT_MASK="/etc/gconf /etc/terminfo /usr/X11R6/lib/X11/xkb /etc/env.d" CXXFLAGS="-O2 -march=pentium3 -mtune=pentium3" DISTDIR="/usr/portage/distfiles" FEATURES="autoaddcvs distcc nostrip sandbox sfperms userpriv" GENTOO_MIRRORS="ftp://gentoo.ccccom.com http://gentoo.ccccom.com http://gentoo.noved.org/" MAKEOPTS="-j4" PKGDIR="/usr/portage/packages" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/usr/portage" PORTDIR_OVERLAY="/usr/local/portage" SYNC="rsync://rsync.gentoo.org/gentoo-portage" USE="X aac acl acpi aim arts artswrappersuid avi berkdb cap chroot crypt cups dga dvd encode escreen ethereal fam fbcon flac foomaticdb gd gdbm gif gtk gtk2 imap imlib innodb jabber jpeg junit kde lcms lesstif libg++ libwww mad maildir mikmod mmx mng motif mpeg ncurses nls nptl odbc offensive oggvorbis opengl oscar oss pam pcmcia pcre pdflib pic png python qt quicktime readline samba sdk sdl slang spell sse ssl svga tcpd theora tiff truetype usb wmf x86 xfs xinerama xml2 xmms xv zlib"
Try adding -mno-mmx to your CFLAGS after the -march line and compiling. There's some MMX code that requires at least gcc-3.4, and it could be broken in some way.
-mno-mmx didn't work, same problem as before. I tried it while upgrading to 6.7.99.903.
This sounds like a gcc bug, not a X bug. Reassigning.
*** This bug has been marked as a duplicate of 57602 ***