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Fix optimization hazard in gram.y's makeOrderedSetArgs(), redux.

It appears that commitcf63c64, which intended to preventmisoptimization of the result-building step in makeOrderedSetArgs,didn't go far enough: buildfarm member hornet's version of xlcis now optimizing back to the old, broken behavior in whichlist_length(directargs) is fetched only after list_concat() haschanged that value. I'm not entirely convinced whether that'san undeniable compiler bug or whether it can be justified by asufficiently 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

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src/backend/parser
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`‎src/backend/parser/gram.y‎`

Lines changed: 3 additions & 3 deletions

Original file line number	Diff line number	Diff line change
`@@ -16075,7 +16075,7 @@ makeOrderedSetArgs(List directargs, List orderedargs,`
`16075`	`16075`	`core_yyscan_t yyscanner)`
`16076`	`16076`	`{`
`16077`	`16077`	`FunctionParameter lastd = (FunctionParameter ) llast(directargs);`
`16078`		`-intndirectargs;`
	`16078`	`+Value *ndirectargs;`
`16079`	`16079`
`16080`	`16080`	`/* No restriction unless last direct arg is VARIADIC*/`
`16081`	`16081`	`if (lastd->mode == FUNC_PARAM_VARIADIC)`
`@@ -16099,10 +16099,10 @@ makeOrderedSetArgs(List directargs, List orderedargs,`
`16099`	`16099`	`}`
`16100`	`16100`
`16101`	`16101`	`/* don't merge into the next line, as list_concat changes directargs*/`
`16102`		`-ndirectargs = list_length(directargs);`
	`16102`	`+ndirectargs =makeInteger(list_length(directargs));`
`16103`	`16103`
`16104`	`16104`	`return list_make2(list_concat(directargs, orderedargs),`
`16105`		`-makeInteger(ndirectargs));`
	`16105`	`+ ndirectargs);`
`16106`	`16106`	`}`
`16107`	`16107`
`16108`	`16108`	`/* insertSelectOptions()`

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Commitdc14aa0

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`‎src/backend/parser/gram.y‎`

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