Bug #12743: throw(false) does not work as expected

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.4.0dev (2016-09-09 trunk 56124) [x86_64-linux]
• Backport: 2.1: UNKNOWN, 2.2: DONE, 2.3: DONE

[rhenium (Kazuki Yamaguchi)]

I expect UncaughtThrowError for these examples:

$ ruby -e'throw false'
-e: unexpected throw
$ ruby -e'Fiber.new{throw false}.resume'
$ ruby -e'Thread.new{throw false}.join'
-e:1: [BUG] thread_join: THROW_DATA should not reach here.
ruby 2.4.0dev (2016-09-09 trunk 56124) [x86_64-linux]

-- Control frame information -----------------------------------------------
<snip>

The cause is that Kernel#throw incorrectly finds a tag that is not created by Kernel#catch, because TH_PUSH_TAG() initializes rb_vm_tag::tag with 0.

The attached patch seems to fix the issue, by making TH_PUSH_TAG() initialize with Qundef that should never appear in Ruby code.

• Status changed from Open to Closed

Applied in changeset r56252.

---

eval_intern.h: make TH_PUSH_TAG() initialize rb_vm_tag::tag with Qundef

• eval_intern.h (TH_PUSH_TAG): Initialize struct rb_vm_tag::tag with
  Qundef rather than 0 which is equal to Qfalse. Since Kernel#throw(obj)
  searches a tag with rb_vm_tag::tag == obj, throw(false) can
  accidentally find an unrelated tag which is not created by
  Kernel#catch. [ruby-core:77229] [Bug #12743]

• test/ruby/test_exception.rb (test_throw_false): Add a test case for
  this.

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN to 2.1: UNKNOWN, 2.2: REQUIRED, 2.3: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.1: UNKNOWN, 2.2: REQUIRED, 2.3: REQUIRED to 2.1: UNKNOWN, 2.2: REQUIRED, 2.3: DONE

ruby_2_3 r56441 merged revision(s) 56252,56254.

[usa (Usaku NAKAMURA)]

• Backport changed from 2.1: UNKNOWN, 2.2: REQUIRED, 2.3: DONE to 2.1: UNKNOWN, 2.2: DONE, 2.3: DONE

ruby_2_2 r56505 merged revision(s) 56252,56254.