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| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | thread.c | 33 |
2 files changed, 39 insertions, 0 deletions
@@ -1,3 +1,9 @@ +Mon Jul 2 22:13:04 2012 Tanaka Akira <akr@fsij.org> + + * thread.c (rb_thread_aref): add explanation for why Thread#[] and + Thread#[]= are fiber-local and not thread-local. + reported by Julien A. [ruby-core:41606] [ruby-trunk - Bug #5750] + Mon Jul 2 21:25:55 2012 Tanaka Akira <akr@fsij.org> * time.c (timew_out_of_timet_range): specialization for @@ -2078,6 +2078,39 @@ rb_thread_local_aref(VALUE thread, ID id) * #<Thread:0x00000002a54220 dead>: A * #<Thread:0x00000002a541a8 dead>: B * #<Thread:0x00000002a54130 dead>: C + * + * Thread#[] and Thread#[]= are not thread-local but fiber-local. + * This confusion was not exist until Ruby 1.8 because + * fiber is available since Ruby 1.9. + * Ruby 1.9 chooses that the methods behaves fiber-local to save + * following idiom for dynamic scope. + * + * def meth(newvalue) + * begin + * oldvalue = Thread.current[:name] + * Thread.current[:name] = newvalue + * yield + * ensure + * Thread.current[:name] = oldvalue + * end + * end + * + * The idiom may not work as dynamic scope if the methods are thread-local + * and a given block switches fiber. + * + * f = Fiber.new { + * meth(1) { + * Fiber.yield + * } + * } + * meth(2) { + * f.resume + * } + * f.resume + * p Thread.current[:name] + * #=> nil if fiber-local + * #=> 2 if thread-local (The value 2 is leaked to outside of meth method.) + * */ static VALUE |