Re: Unixware Patch (Was: Re: Beta2 Tag'd and Bundled ...) - Mailing list pgsql-hackers

Greg Stark wrote:
> Peter Eisentraut <peter_e@gmx.net> writes:
> 
> > Lee Kindness writes:
> > 
> > > You don't... and you simply shouldn't care. If there is a_r version
> > > available then we should use it - even if the plain version is "safe".
> > 
> > The problem with this is that the automatic determination (in configure)
> > whether there is a xxx_r()  version is, in general, fragile.  We cannot
> > rely on configure saying that xxx_r() doesn't exist, so the plain xxx()
> > should be good enough.  Else, we'd be shipping claimed-to-be-thread-safe
> > libraries that might trigger bugs that will be hard to track down.
> 
> Um. I don't think that's true. I mean, in theory it's true, but in practice
> why would an OS have some *_r but have only non-thread-safe versions of
> others?

Oh, interesting.  So you are saying that if the OS supports threads,
then we use the *_r if they have them, and assume the non *_r functions
are already thread-safe if they don't.  Interesting.

That seems to be what we have on Unixware, and on BSD/OS I have some *_r
functions but not others, but they are all threadsafe, so your plan
works there too.

> The only OSes like that would be ones that were in the process of developing
> thread-safe libraries and hadn't finished yet. Perhaps early versions of
> Solaris or CVS snapshots of BSD? I don't know of any actual releases that
> anyone would want to be running today.
> 
> Postgres doesn't need to work around problems like that. At worst it should
> have a blacklist of OS versions that it knows not to even bother building a
> threadsafe libpq for.

We could go down that road.  The only other OS that needs *_r functions
is Linux, and it uses all *_r functions.  How do we configure to throw
an error in that OS if we don't fined all of them?  Maybe we need a
three-valued variable instead of boolean NEED_REENTRANT_FUNC_NAMES.  We
could call it just REENTRANT_FUNC_NAMES and it could have values
'require', 'prefer', 'disable'.  This mimicks libpq's new PGSSLMODE
values.

That sounds like a clear plan.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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