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

[Daniel Colascione]

>> 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.  ]

Sure. And at that point, we might as well make compiled patterns into
GC-able heap objects. That's probably a good idea, but it's a bigger
project.