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Avoid formally-undefined use of memcpy() in hstoreUniquePairs().

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hstoreUniquePairs() often called memcpy with equal source and destination
pointers.  Although this is almost surely harmless in practice, it's
undefined according to the letter of the C standard.  Some versions of
valgrind will complain about it, and some versions of libc as well
(cf. commit ad520ec4a).  Tweak the code to avoid doing that.

Noted by Tomas Vondra.  Back-patch to all supported versions because
of the hazard of libc assertions.

Discussion: https://postgr.es/m/bf84d940-90d4-de91-19dd-612e011007f4@fuzzy.cz
This commit is contained in:
Tom Lane 2017-11-25 14:42:10 -05:00
parent 497e79b961
commit 630aceda5b
1 changed files with 2 additions and 1 deletions
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3
contrib/hstore/hstore_io.c
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@ -340,7 +340,8 @@ hstoreUniquePairs(Pairs *a, int32 l, int32 *buflen)
{
*buflen += res->keylen + ((res->isnull) ? 0 : res->vallen);
res++;
memcpy(res, ptr, sizeof(Pairs));
if (res != ptr)
memcpy(res, ptr, sizeof(Pairs));
}
ptr++;