> The new Str module not only made it LGPL but also very fast (100% more
> than Pcre in some cases).  However it is still not thread safe -- and
> it is not possible given its interface.  However, from a quick look,
> it seems to me that what is under the hood is almost thread safe.

You are correct: the regexp compiler (written in Caml) and the
execution engine (written in C) are thread-safe, it's only the API (in
Caml) that uses global state.

> So why not to write a new module (say Regexp) which would be thread
> safe and on top of which Str would be build?

That's a very good idea.  My initial plan was to have two APIs, the
old Str for compatibility and a newer, better designed one for new
programs.  Besides being thread-safe, the new API could also expose
the abstract syntax tree for regexps, allowing easier construction of
complex regexps by programs than can be done by working at the level
of the string representation of regexps.  It's just that I never got
to design that new API :-(

> This would not be too much work, would it?

The implementation work should be quite small indeed, but don't
underestimate the work needed to design the API.  API design is harder
than it seems...  But if a few persons on this list want to team up to
design an API, that would be wonderful indeed.  (A small group is
better than individual designers in that several pairs of eyes spot
inconsistencies better.)

- Xavier Leroy