Reporting X server crashes

Useful backtraces will help identify where and why the crash is occurring, which will help us fix the bug.

Automatically reporting crashes

• Install the xorg-server-cygwin-crashreporter package
• Reproduce your crash

This should automatically start a crash reporter, which will generate and upload a minidump file containing information about the crash.

In some cases, this doesn't work (for reasons still under investigation), in which case see the following section.

Manually producing a crash backtrace

To generate a useful backtrace, you will need debugging symbols for the X server.

Preparation

• Install the xorg-server-debuginfo package (for debugging symbols)
• Install the gdb package (for gdb)
• Install the sysvinit package (for pidof)

Generating a backtrace when some specific action is making the X server crash (automatically)

• Start XWin using your normal method
• Reproduce your crash
• A backtrace should be captured into /var/log/xwin/XWin.0.log

Generating a backtrace when some specific action is making the X server crash (manually)

• Start XWin using your normal method
• In a non-X terminal window, run gdb --pid=`pidof /usr/bin/XWin`, to attach gdb to the running X server
• Type c at the (gdb) prompt, to resume running the X server
• Reproduce your crash
• Type bt full at the (gdb) prompt, to produce a backtrace

Generating a backtrace when the X server is crashing at startup

• In a non-X terminal window, run gdb --args /usr/bin/XWin -multiwindow, to start the X server under gdb (If you have customized how you start XWin to add additional options, you should also add them here)
• Type handle SIGSYS nostop at the (gdb) prompt
• Type r at the (gdb) prompt, to start running the X server
• Your crash should occur
• Type bt full at the (gdb) prompt, to produce a backtrace

Generating a backtrace when the X server is crashing at startup (alternative approach using JIT debugging)

• Set the error_start token in the CYGWIN environment variable to run gdb, e.g. CYGWIN="error_start=C:\cygwin\bin\gdb" (If you are going to start the X server using a Windows shortcut, you will have to set this in the System applet of the Windows control panel)
• Start XWin using your normal method
• Your crash should occur
• Type bt full at the (gdb) prompt, to produce a backtrace

Please attach the output from gdb, in addition to your /var/log/xwin/XWin.0.log, to your problem report.

Cleaning up

• Uninstall the xorg-server-debuginfo package
• Uninstall the gdb and sysvinit packages if you no longer need them
• Restore the previous value of the CYGWIN environment variable, if you changed it

Preparation (alternative approach)

Alternatively, X server snapshots are built with debugging symbols included. You can install an X server snapshot with the following steps:

• Download the latest X Server snapshot from ftp://cygwin.com/pub/cygwinx
  wget ftp://cygwin.com/pub/cygwinx/XWin.YYYMMDD-git-XXXXXXXXXXXXXXXX.exe.bz2
• Uncompress it
  bunzip2 XWin.YYYMMDD-git-XXXXXXXXXXXXXXXX.exe.bz2
• Ensure it is executable
  chmod +x XWin.YYYMMDD-git-XXXXXXXXXXXXXXXX.exe
• Move it to /usr/bin
  mv XWin.YYYMMDD-git-XXXXXXXXXXXXXXXX.exe /usr/bin/XWin.exe

To remove the X server snapshot, use setup to reinstall the xorg-server package