Robustify tuplesort's free_sort_tuple function

david-rowley · david-rowley · commit 2fde8e49a247 · 2021-07-13T13:28:19.000+12:00
4146925 went to the trouble of removing a theoretical bug from free_sort_tuple by checking if the tuple was NULL before freeing it. Let's make this a little more robust by also setting the tuple to NULL so that should we be called again we won't end up doing a pfree on the already pfree'd tuple. Per advice from Tom Lane. Discussion: https://postgr.es/m/3188192.1626136953@sss.pgh.pa.us Backpatch-through: 9.6, same as 4146925
diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
@@ -4701,5 +4701,6 @@ free_sort_tuple(Tuplesortstate *state, SortTuple *stup)
 	{
 		FREEMEM(state, GetMemoryChunkSpace(stup->tuple));
 		pfree(stup->tuple);
+		stup->tuple = NULL;
 	}
 }

Original file line number	Diff line number	Diff line change
`@@ -4701,5 +4701,6 @@ free_sort_tuple(Tuplesortstate state, SortTuple stup)`
`4701`	`4701`	`{`
`4702`	`4702`	`FREEMEM(state, GetMemoryChunkSpace(stup->tuple));`
`4703`	`4703`	`pfree(stup->tuple);`
	`4704`	`+ stup->tuple = NULL;`
`4704`	`4705`	`}`
`4705`	`4706`	`}`