Fix optimization hazard in gram.y's makeOrderedSetArgs(), redux.
authorTom Lane
Wed, 7 Oct 2020 22:41:39 +0000 (18:41 -0400)
committerTom Lane
Wed, 7 Oct 2020 22:42:30 +0000 (18:42 -0400)
commit9f3d3fb8702b51f028280b36f8d9abbdd253dc41
treecd13ec1ba793d74a30de1094268a08bbcf876832
parent0c79dcb36c525234f1ffbab601f6f9716b8ca43a
Fix optimization hazard in gram.y's makeOrderedSetArgs(), redux.

It appears that commit cf63c641c, which intended to prevent
misoptimization of the result-building step in makeOrderedSetArgs,
didn't go far enough: buildfarm member hornet's version of xlc
is now optimizing back to the old, broken behavior in which
list_length(directargs) is fetched only after list_concat() has
changed that value.  I'm not entirely convinced whether that's
an undeniable compiler bug or whether it can be justified by a
sufficiently aggressive interpretation of C sequence points.
So let's just change the code to make it harder to misinterpret.

Back-patch to all supported versions, just in case.

Discussion: https://postgr.es/m/1830491.1601944935@sss.pgh.pa.us
src/backend/parser/gram.y