[ruby-cvs:78750] 8e56d3a6ab (master): Define PREV_CLASS_SERIAL

John Hawthorn	2019-12-13 09:42:34 +0900 (Fri, 13 Dec 2019)

  New Revision: 8e56d3a6ab

  https://github.com/ruby/ruby/commit/8e56d3a6ab

  Log:
    Define PREV_CLASS_SERIAL
    
    Avoids genereating a "throwaway" sentinel class serial. There wasn't any
    read harm in doing so (we're at no risk of exhaustion and there'd be no
    measurable performance impact), but if feels cleaner that all class
    serials actually end up assigned and used (especially now that we won't
    overwrite them in a single method definition).

  Modified files:
    vm_insnhelper.h
    vm_method.c