Hello hackers,
Using Svace* I think I've found a little bug in src/backend/utils/mmgr/dsa.c.
This bug is presented in REL_12_STABLE, REL_13_STABLE, REL_14_STABLE,
REL_15_STABLE, REL_16_STABLE and master. I see that it was introduced together
with dynamic shared memory areas in the commit
13df76a537cca3b8884911d8fdf7c89a457a8dd3.
I also see that at least two people have encountered this fprintf output.
(https://postgrespro.com/list/thread-id/2419512,
https://www.postgresql.org/message-id/15e9501170d.e4b5a3858707.3339083113985275726%40zohocorp.com)
fprintf(stderr,
" segment bin %zu (at least %d contiguous pages free):\n",
i, 1 << (i - 1));
In case i equals zero user will get "at least -2147483648 contiguous pages
free".
I believe that this is a mistake, and fprintf should print "at least 0
contiguous pages free"
in case i equals zero.
The patch that has a fix of this is attached.
* - https://svace.pages.ispras.ru/svace-website/en/
Kind regards,
Ian Ilyasov.
Juniour Software Developer at Postgres Professional
Subject: [PATCH] Integer underflow fix in fprintf in dsa.c.
---
Index: src/backend/utils/mmgr/dsa.c
<+>UTF-8
===================================================================
diff --git a/src/backend/utils/mmgr/dsa.c b/src/backend/utils/mmgr/dsa.c
--- a/src/backend/utils/mmgr/dsa.c (revision b78fa8547d02fc72ace679fb4d5289dccdbfc781)
+++ b/src/backend/utils/mmgr/dsa.c (date 1708426298001)
@@ -1107,7 +1107,7 @@
fprintf(stderr,
" segment bin %zu (at least %d contiguous pages free):\n",
- i, 1 << (i - 1));
+ i, i != 0 ? 1 << (i - 1) : 0);
segment_index = area->control->segment_bins[i];
while (segment_index != DSA_SEGMENT_INDEX_NONE)
{
