Hi,

For those of you that have not yet upgraded to Mavericks and occasionally develop code or run ROOT locally, you might consider waiting a bit before upgrading. For those that could not wait to get the new OS (like myself), below are some instructions to re-install ROOT. In case you find mistakes or misconceptions please correct them.

o First, why to reinstall ROOT in Mavericks. When compiling something in ROOT you will probably encounter:
"Undefined symbols for architecture x86_64"
When this happens, this means you need to reinstall ROOT.

o Prepare for re-installing ROOT from source after Mavericks update. You need to (re-)install the command-line tools for Xcode:

xcode-select --install

Then remove XQuartz and reinstall the latest version (download from web or App Store). You need to do this even if you already had the latest version *before* upgrading to OS X Mavericks. Visit:
  http://xquartz.macosforge.org/landing/

o Install ROOT from source. It seems that you need to get the latest ROOT patches, otherwise PyROOT will crash.
git clone -b v5-34-00-patches http://root.cern.ch/git/root.git root-v5-34-00-patches
cd root-v5-34-00-patches
./configure macosx64 --enable-roofit
make -j6
source bin/thisroot.sh

o In case you use PyROOT, you will notice that the X windows are not appearing. This is because PyROOT thinks it is running in batch. The workaround is to add at the start of your script, or in a .pythonrc file:
  import ROOT
  ROOT.gROOT.SetBatch(False)
After that you can do things like
  from ROOT import *
  TBrowser()
in your scripts. See https://sft.its.cern.ch/jira/browse/ROOT-5673 and http://root.cern.ch/phpBB3/viewtopic.php?f=14&t=17238

It took me 1.5 days to get this working. I hope this saves some of your time.

Cheers
Jeroen