Accumulated work on fsc.

adds the following new options.

  -ipv4 Use IPv4 rather than IPv6 for the server socket absolute-cp Make
  -classpath elements absolute paths before sending to server max-idle
  -Set idle timeout in minutes for fsc (use 0 for no timeout)

My question marks are what are the right defaults for the first two.
Former behavior is to absolutize the classpath always and never prefer
IPv4 sockets. I changed the default to not absolutize the classpath,
with the option if you need it; I left the system default in place for
the socket creation, but I have a feeling we should default to IPv4. My
only hesitation is that the only way to request an IPv4 socket from java
involves mutating a global system property. (Robustness FTW.) So for
now, you have to give -ipv4.

Closes #3626, #3785, #3788, #3789. Review by community.

1 files changed, 10 insertions, 4 deletions

diff --git a/src/library/scala/sys/SystemProperties.scala b/src/library/scala/sys/SystemProperties.scala
index 7c6286516b..228ca6315e 100644
--- a/src/library/scala/sys/SystemProperties.scala
+++ b/src/library/scala/sys/SystemProperties.scala
@@ -48,9 +48,14 @@ class SystemProperties extends mutable.Map[String, String] {
  *  }}}
  */
 object SystemProperties {
+  /** An unenforceable, advisory only place to do some synchronization when
+   *  mutating system properties.
+   */
+  def exclusively[T](body: => T) = this synchronized body
+
   implicit def systemPropertiesToCompanion(p: SystemProperties): SystemProperties.type = this
   private lazy val propertyHelp = mutable.Map[String, String]()
-  private def bool(key: String, helpText: String) = {
+  private def bool(key: String, helpText: String): BooleanProp = {
     val prop = (
       if (key startsWith "java.") BooleanProp.valueIsTrue(key)
       else BooleanProp.keyExists(key)
@@ -63,8 +68,9 @@ object SystemProperties {
   // Todo: bring some sanity to the intersection of system properties aka "mutable
   // state shared by everyone and everything" and the reality that there is no other
   // mechanism for accomplishing some things on the jvm.
-  lazy val headless          = bool("java.awt.headless", "system should not utilize a display device")
-  lazy val preferIPv4        = bool("java.net.preferIPv4Stack", "system should prefer IPv4 sockets")
-  lazy val noTraceSupression = bool("scala.control.no-trace-suppression", "scala should not suppress any stack trace creation")
+  lazy val headless            = bool("java.awt.headless", "system should not utilize a display device")
+  lazy val preferIPv4Stack     = bool("java.net.preferIPv4Stack", "system should prefer IPv4 sockets")
+  lazy val preferIPv6Addresses = bool("java.net.preferIPv6Addresses", "system should prefer IPv6 addresses")
+  lazy val noTraceSupression   = bool("scala.control.noTraceSuppression", "scala should not suppress any stack trace creation")
 }