After upgrading Jenkins to 1.599 all executors start dying because of the error below. All my jobs are configured to discard old builds.

java.lang.IllegalStateException: cannot create a build with number 1447 since that (or higher) is already in use among [1415, 1416, 1417, 1418, 1419, 1420, 1421, 1422, 1423, 5288]
at jenkins.model.lazy.AbstractLazyLoadRunMap.proposeNewNumber(AbstractLazyLoadRunMap.java:361)
at hudson.model.RunMap.put(RunMap.java:189)
at jenkins.model.lazy.LazyBuildMixIn.newBuild(LazyBuildMixIn.java:178)
at hudson.model.AbstractProject.newBuild(AbstractProject.java:1006)
at hudson.model.AbstractProject.createExecutable(AbstractProject.java:1205)
at hudson.model.AbstractProject.createExecutable(AbstractProject.java:144)
at hudson.model.Executor.run(Executor.java:213)

I could see that the method SortedIntList.isInRange does not check the list content. So I changed it to the code below and everything worked fine.

public boolean isInRange(int idx)

I will make a pull request with this solution.