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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2020-10-07 18:41:39 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2020-10-07 18:42:12 -0400 |
| commit | 8b231d9753287fc16328af2ab31943b79e1cc8a3 (patch) | |
| tree | 9fdd116bc6f242cec9787d3cfc3c3a4824bbab8d | |
| parent | d8c2a2199867460ff65796be37eecff56426136b (diff) | |
| download | postgresql-8b231d9753287fc16328af2ab31943b79e1cc8a3.tar.gz postgresql-8b231d9753287fc16328af2ab31943b79e1cc8a3.zip | |
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
| -rw-r--r-- | src/backend/parser/gram.y | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y index 208b4a1f28a..32797728d2e 100644 --- a/src/backend/parser/gram.y +++ b/src/backend/parser/gram.y @@ -15817,7 +15817,7 @@ 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) @@ -15841,10 +15841,10 @@ 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() |