Make Thread#join always convert its argument, as before 70f08f1eed

spec/ruby/core/thread/join_spec.rb

@@ -22,11 +22,10 @@ describe "Thread#join" do
   end
 
   it "raises TypeError if the argument is not a valid timeout" do
-    t = Thread.new { sleep }
+    t = Thread.new { }
+    t.join
     -> { t.join(:foo) }.should raise_error TypeError
     -> { t.join("bar") }.should raise_error TypeError
-    t.kill
-    t.join
   end
 
   it "returns nil if it is not finished when given a timeout" do

thread.c

@@ -1313,6 +1313,17 @@ thread_join_m(int argc, VALUE *argv, VALUE self)
         timeout = argv[0];
     }
 
+    // Convert the timeout eagerly, so it's always converted and deterministic
+    if (timeout == Qnil) {
+        /* unlimited */
+    }
+    else if (FIXNUM_P(timeout)) {
+        /* handled directly in thread_join_sleep() */
+    }
+    else {
+        timeout = rb_to_float(timeout);
+    }
+
     return thread_join(rb_thread_ptr(self), timeout);
 }