Re: [Emacs-diffs] master 938d252 4/4: Make regex matching reentrant; update syntax during match

[Stefan Monnier]

> Oh, yeah. One more thing. The busy flag isn't *just* to prevent the regex
> bytecode engine confusing itself with self-modifying bytecode. It also
> serves to protect the cache slot holding the regex pattern from reuse,
> which would be disastrous whether or not the bytecode of a particular
> pattern happens to be mutable.

It doesn't have to be disastrous *if* we complexify the code such that
removing a pattern from the cache doesn't inevitably free that pattern ;-)
[ But, yes, we'd still need to mark the pattern as "busy" in order to
  know when it can be freed.  ]


        Stefan