| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
| Cc: | Boszormenyi Zoltan <zb(at)cybertec(dot)at>, Michael Meskes <meskes(at)postgresql(dot)org>, pgsql-hackers(at)postgresql(dot)org, Hans-Juergen Schoenig <hs(at)cybertec(dot)at> |
| Subject: | Re: Question about ECPGset_noind_null() and ECPGis_noind_null() |
| Date: | 2009-11-19 20:51:12 |
| Message-ID: | 29461.1258663872@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> Boszormenyi Zoltan wrote:
>> Is it *really* a bug? I recalled a comment from my C teacher
>> in '92 or '93 about this exact issue, that the prefix/postfix
>> increment/decrement operators are executed in the
>> statement in an implementation-defined order,
> Not if they come after a short-circuit operator such as && - after all,
> that's what short-circuit evaluation implies. If the left hand operand
> of && is false the right hand should not be evaluated at all.
Yes. && is a sequence point and the compiler is not allowed to move
side-effects across a sequence point. What your C teacher was warning
you against was things like
a[i] = i++;
'=' is not a sequence point so it's undefined which array index
will be stored into.
regards, tom lane
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