some problems with JRuby seeming to not detect Java Long arithmetic overflows

There seem to be some bugs where the Java code underlying JRuby seems to not detect Long arithmetic overflows.

For example, on my PCs running this code in JRuby:

nn = -(2**63)-1
3.times {|i| i += nn; puts "# i: #{i}; i*-1: #{i*-1}; -1*i: #{-1*i}" }

results in this output:

# i: -9223372036854775809; i*-1: 9223372036854775809; -1*i: 9223372036854775809
# i: -9223372036854775808; i*-1: 9223372036854775808; -1*i: -9223372036854775808
# i: -9223372036854775807; i*-1: 9223372036854775807; -1*i: 9223372036854775807

I seem to have some problems with Fixnum multiplication (as above),
and with Fixnum/Bignum Range#each and Range#each_with_index.

There are more examples and information in the attached JRuby file.

My apologies if I am making a mistake, or if these issues have been raised before: I searched jira.codehaus.org using "JRuby overflow", but didn't find anything that seemed to cover the examples in the attached file.

I wasn't sure what priority to give this: if I'm correct that these are bugs with Fixnum (etc) then they would seem to be "major", but if no-one else has noticed these before then in practice there hasn't so far been a problem.

In the attached file I've put a possible patch for one occurrence of the Fixnum multiply overflow problem, but there may be other places where patches are needed, and there is also the Fixnum/Bignum range problem: I'm afraid I haven't looked at all at the JRuby Java code for that.

I would be happy to give more details and/or answer any questions.