Merge pull request RobotLocomotion#1188 from peteflorence/ipv4

warn to use ipv4 on OSX

drake/addpath_drake.m

@@ -59,6 +59,21 @@
 
 javaaddpath(fullfile(pods_get_base_path,'share','java','drake.jar'));
 
+% OSX platform-specific: check if reverted to IPv4
+if (computer('arch') == 'maci64')
+  ipv4_preferred = java.lang.System.getProperty('java.net.preferIPv4Stack');
+  if isempty(ipv4_preferred)
+    ipv4_preferred = 'false';
+  end
+  if (ipv4_preferred ~= 'true')
+    display('WARNING: Your JVM may crash if you do not set it to prefer IPv4 over IPv6.')
+    display('This may cause any dependencies that involve the JVM (including LCM) to crash at runtime.')
+    display('Please see bug report and solution here: https://github.com/RobotLocomotion/drake/issues/558.')
+    display('(It just involves adding one line to your java.opts file for Matlab.)')
+    display('Make sure to restart Matlab after editing your java.opts file.')
+  end
+end
+
 if ispc 
   setenv('PATH',[getenv('PATH'),';',GetFullPath(pods_get_lib_path),';',fullfile(root,'pod-build','lib','Release'),';',fullfile(root,'pod-build','lib')]);
 end