postgres.git / summary / log / commit / refs
commit abfce4e46870dfab0e16afae254802b4eb920377
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed Oct 07 22:41:39 2020 +0000
First released in: 14.0, 9.5.24, 9.6.20, 10.15, 11.10, 12.5, 13.1
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 | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 96910cf6edd..e5c51c5e159 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -14385,7 +14385,7 @@ makeOrderedSetArgs(List *directargs, List *orderedargs,
core_yyscan_t yyscanner)
{
FunctionParameter *lastd = (FunctionParameter *) llast(directargs);
- int ndirectargs;
+ Value *ndirectargs;
/* No restriction unless last direct arg is VARIADIC */
if (lastd->mode == FUNC_PARAM_VARIADIC)
@@ -14409,10 +14409,10 @@ makeOrderedSetArgs(List *directargs, List *orderedargs,
}
/* don't merge into the next line, as list_concat changes directargs */
- ndirectargs = list_length(directargs);
+ ndirectargs = makeInteger(list_length(directargs));
return list_make2(list_concat(directargs, orderedargs),
- makeInteger(ndirectargs));
+ ndirectargs);
}
/* insertSelectOptions()
[parent: 0bfe356c5594]