* string.c (fstr_update_callback): Improve implementation in r43968
  based on feedback from @nagachika. In the existing case, we can
  return ST_STOP to prevent any hash modification. In the !existing
  case, set both key and value to the fstr.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43986 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* vm_trace.c (rb_suppress_tracing): Fix initialization of stack
  allocated rb_trace_arg_t structure. Without this patch, sometimes
  INTERNAL_EVENT_GC would be skipped accidentally inside
  rb_threadptr_exec_event_hooks_orig().

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43987 b2dd03c8-39d4-4d8f-98ff-823fe69b080e