Re: [Chicken-users] difference between ##sys#error and posix-error?

[Christian Kellermann]

* Alaric Snell-Pym <address@hidden> [110929 13:18]:
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> On 09/29/2011 08:36 AM, Christian Kellermann wrote:
> > Hi Alan!
> >
> > * Alan Post <address@hidden> [110929 05:51]:
> >> Looking at posixunix.scm, I find that some error messages are
> >> produced with ##sys#error, and others with posix-error.  What
> >> distinguishes these two routines?  Why would I use one but not
> >> the other?
> >
> > (define posix-error
> >   (let ([strerror (foreign-lambda c-string "strerror" int)]
> >     [string-append string-append] )
> >     (lambda (type loc msg . args)
> >       (let ([rn (##sys#update-errno)])
> >     (apply ##sys#signal-hook type loc (string-append msg " - " (strerror 
> > rn)) args) ) ) ) )
> 
> 
> Ooof, is that correct? IIRC, strerror isn't thread safe. We may not be
> using POSIX threads, but might Chicken not schedule a new thread between
> strerror and string-append, which might itself call strerror and thus
> produce an invalid error message? I'm not sure at what points the
> scheduler is actually able to preempt.
> 
> The solution, if that is a potential problem, is strerror_r, where you
> pass in your own string buffer.

posix unit declares disable-interrupts which does:

Disable timer-interrupts checks in the compiled program. Threads
can not be preempted in main- or library-units that contain this
declaration.

Does this help your understanding? Should be safe IMHO.

Kind regards,

Christian

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