thread.c (thread_join_m): handle negative timeouts correctly

Users may subtract and round into negative values when using
Thread#join, so clamp the timeout to zero to avoid infinite/long
timeouts.

Note: other methods such as Kernel#sleep and IO.select will
raise on negative values, but Thread#join is an outlier *shrug*

This restores Ruby 2.5 (and earlier) behavior.

Fixes: r62182 (commit c915390b9530c31b4665aacf27c1adfc114f768e)
       ("thread.c: avoid FP for Thread#join")

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62462 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 7 insertions, 0 deletions

diff --git a/test/ruby/test_thread.rb b/test/ruby/test_thread.rb
index 2d84ee3a6d..921f5a01c1 100644
--- a/test/ruby/test_thread.rb
+++ b/test/ruby/test_thread.rb
@@ -234,6 +234,13 @@ class TestThread < Test::Unit::TestCase
       t = Thread.new {}
       assert_same t, t.join(limit), "limit=#{limit.inspect}"
     end
+    t = Thread.new { sleep }
+    [ -1, -0.1, RbConfig::LIMITS['FIXNUM_MIN'], RbConfig::LIMITS['INT64_MIN'],
+      -Float::INFINITY
+    ].each do |limit|
+      assert_nil t.join(limit), "limit=#{limit.inspect}"
+    end
+    t.kill
   end
 
   def test_kill_main_thread