Robustify tuplesort's free_sort_tuple function

david-rowley · david-rowley · commit 5bd38d2f2846 · 2021-07-13T13:27:05.000+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
@@ -4777,5 +4777,6 @@ 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
`@@ -4777,5 +4777,6 @@ free_sort_tuple(Tuplesortstate state, SortTuple stup)`
`4777`	`4777`	`{`
`4778`	`4778`	`FREEMEM(state, GetMemoryChunkSpace(stup->tuple));`
`4779`	`4779`	`pfree(stup->tuple);`
	`4780`	`+ stup->tuple = NULL;`
`4780`	`4781`	`}`
`4781`	`4782`	`}`