* 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.
merge revision(s) 56252,56254: [Backport #12743]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@56441 b2dd03c8-39d4-4d8f-98ff-823fe69b080e