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

[Alaric Snell-Pym]

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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.

ABS

- --
Alaric Snell-Pym
http://www.snell-pym.org.uk/alaric/
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