Comment 7 for bug 336320

@Bryce: I've found a way to make X crash almost systematically, so I am in a position to get a full backtrace. However, I followed https://wiki.ubuntu.com/X/Backtracing and I have missing symbols at the top of the backtrace, which is no good:

(gdb) backtrace full
#0 0xb13d7aee in ?? () from /usr/lib/dri/r300_dri.so
No symbol table info available.
#1 0xb13d7e21 in _mesa_update_texture () from /usr/lib/dri/r300_dri.so
No symbol table info available.
#2 0xb13c1fb6 in _mesa_update_state_locked () from /usr/lib/dri/r300_dri.so
No symbol table info available.
#3 0xb13c21aa in _mesa_update_state () from /usr/lib/dri/r300_dri.so
No symbol table info available.
#4 0xb1494148 in _mesa_GetIntegerv () from /usr/lib/dri/r300_dri.so
No symbol table info available.
#5 0xb78b3132 in __glXDRIbindTexImage (baseContext=0x9cccd88, buffer=8414,
    glxPixmap=0xa421b18) at ../../glx/glxdri.c:406
        pRegion = <value optimized out>
        pixmap = <value optimized out>
        bpp = <value optimized out>
        override = <value optimized out>
        texname = -1215888936
        format = <value optimized out>
        type = <value optimized out>
        pScreen = (ScreenPtr) 0x9b0d658
        __func__ = "__glXDRIbindTexImage"
#6 0xb78a52e8 in __glXDisp_BindTexImageEXT (cl=0x9cb5be0,
    pc=0xa66aa05c "\232\020\006") at ../../glx/glxcmds.c:1535
        client = (ClientPtr) 0x9cb7818
        context = <value optimized out>
        pGlxDraw = (__GLXdrawable *) 0x9d63660
        drawId = 16780418
        error = <value optimized out>
#7 0xb78a41a7 in __glXDisp_VendorPrivate (cl=0x9cb5be0,
    pc=0xa66aa05c "\232\020\006") at ../../glx/glxcmds.c:2250
No locals.
#8 0xb78a8d6a in __glXDispatch (client=0x9cb7818) at ../../glx/glxext.c:523
        stuff = (xGLXSingleReq *) 0xa66aa05c
        opcode = 16 '\020'
        cl = (__GLXclientState *) 0x9cb5be0
        retval = 1
#9 0x0808d5af in Dispatch () at ../../dix/dispatch.c:437
        result = <value optimized out>
        client = (ClientPtr) 0x9cb7818
        nready = 0
        start_tick = 29600
#10 0x0807231d in main (argc=10, argv=0xbfa54f44, envp=0x9d84bc0)
    at ../../dix/main.c:397
        i = <value optimized out>
        alwaysCheckForInput = {0, 1}

If I understood the guide correctly, I only had to install xserver-xorg-core-dbg, libgl1-mesa-dri-dbg and xserver-xorg-video-ati-dbg, after which (I assume) my next X session would use the dbg binaries and libraries. Or do I need to do something else? There is a r300_dri.so in libgl1-mesa-dri-dbg, so there's something I must be doing wrong...