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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
- gram.y

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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
`@@ -16291,7 +16291,7 @@ makeOrderedSetArgs(List directargs, List orderedargs,`
`16291`	`16291`	`core_yyscan_t yyscanner)`
`16292`	`16292`	`{`
`16293`	`16293`	`FunctionParameter lastd = (FunctionParameter ) llast(directargs);`
`16294`		`-intndirectargs;`
	`16294`	`+Value *ndirectargs;`
`16295`	`16295`
`16296`	`16296`	`/* No restriction unless last direct arg is VARIADIC*/`
`16297`	`16297`	`if (lastd->mode == FUNC_PARAM_VARIADIC)`
`@@ -16315,10 +16315,10 @@ makeOrderedSetArgs(List directargs, List orderedargs,`
`16315`	`16315`	`}`
`16316`	`16316`
`16317`	`16317`	`/* don't merge into the next line, as list_concat changes directargs*/`
`16318`		`-ndirectargs = list_length(directargs);`
	`16318`	`+ndirectargs =makeInteger(list_length(directargs));`
`16319`	`16319`
`16320`	`16320`	`return list_make2(list_concat(directargs, orderedargs),`
`16321`		`-makeInteger(ndirectargs));`
	`16321`	`+ ndirectargs);`
`16322`	`16322`	`}`
`16323`	`16323`
`16324`	`16324`	`/* insertSelectOptions()`

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Commit8d2a01a

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`‎src/backend/parser/gram.y‎`

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