Sorry, still too unspecific for a bug report. Did somebody else see this? [original report at http://bugs.debian.org/196090]
Compiling xfree-4.2.1 and xfree-4.3 breaks the X server such that XDM-AUTHORIZATION-1 Xauth tokens can not be validated. Seen at least on i386-linux and powerpc-linux. I.e. trying to start xdm shows the following errors: AUDIT: Mon Jun 9 12:03:40 2003: 7369 X: client 2 rejected from local host Auth name: XDM-AUTHORIZATION-1 ID: -1 Compiling with -O instead of -O2 made the problem go away. Compiling with -O2 -fno-strict-aliasing still shows the error (for xfree86-4.2.1).