postgres.git / summary / log / commit / refs

commit    fb7ed3889fa6fc0f4aa6718ffb6574801ad12484
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Sat Sep 10 17:49:04 2016 +0000
First released in: 10.0, 9.4.10, 9.5.5, 9.6.0

    Fix miserable coding in pg_stat_get_activity().
    
    Commit dd1a3bccc replaced a test on whether a subroutine returned a
    null pointer with a test on whether &pointer->backendStatus was null.
    This accidentally failed to fail, at least on common compilers, because
    backendStatus is the first field in the struct; but it was surely trouble
    waiting to happen.  Commit f91feba87 then messed things up further,
    changing the logic to
    
    	local_beentry = pgstat_fetch_stat_local_beentry(curr_backend);
    	if (!local_beentry)
    		continue;
    	beentry = &local_beentry->backendStatus;
    	if (!beentry)
    	{
    
    where the second "if" is now dead code, so that the intended behavior of
    printing a row with "<backend information not available>" cannot occur.
    
    I suspect this is all moot because pgstat_fetch_stat_local_beentry
    will never actually return null in this function's usage, but it's still
    very poor coding.  Repair back to 9.4 where the original problem was
    introduced.


 src/backend/utils/adt/pgstatfuncs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 44ccd37e998..688eea12a93 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -633,15 +633,13 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 		{
 			/* Get specific pid slot */
 			local_beentry = pgstat_fetch_stat_local_beentry(*(int *) (funcctx->user_fctx));
-			beentry = &local_beentry->backendStatus;
 		}
 		else
 		{
 			/* Get the next one in the list */
 			local_beentry = pgstat_fetch_stat_local_beentry(funcctx->call_cntr + 1);	/* 1-based index */
-			beentry = &local_beentry->backendStatus;
 		}
-		if (!beentry)
+		if (!local_beentry)
 		{
 			int			i;
 
@@ -655,6 +653,8 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 			SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
 		}
 
+		beentry = &local_beentry->backendStatus;
+
 		/* Values available to all callers */
 		values[0] = ObjectIdGetDatum(beentry->st_databaseid);
 		values[1] = Int32GetDatum(beentry->st_procpid);


[parent: 8778da2af0f4]