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commit    24dc4afebd5a82f30aed6bd18d48ff42ef787410
Author:   Daniel Gustafsson <dgustafsson@postgresql.org>
Date:     Thu Feb 29 11:19:52 2024 +0000
First released in: 17.0, 12.19, 13.15, 14.12, 15.7, 16.3

    Fix integer underflow in shared memory debugging
    
    dsa_dump would print a large negative number instead of zero for
    segment bin 0.  Fix by explicitly checking for underflow and add
    special case for bin 0. Backpatch to all supported versions.
    
    Author: Ian Ilyasov <ianilyasov@outlook.com>
    Reviewed-by: Robert Haas <robertmhaas@gmail.com>
    Discussion: https://postgr.es/m/GV1P251MB1004E0D09D117D3CECF9256ECD502@GV1P251MB1004.EURP251.PROD.OUTLOOK.COM
    Backpatch-through: v12


 src/backend/utils/mmgr/dsa.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/backend/utils/mmgr/dsa.c b/src/backend/utils/mmgr/dsa.c
index 35e166dd3db..564995db79e 100644
--- a/src/backend/utils/mmgr/dsa.c
+++ b/src/backend/utils/mmgr/dsa.c
@@ -1093,9 +1093,13 @@ dsa_dump(dsa_area *area)
 		{
 			dsa_segment_index segment_index;
 
-			fprintf(stderr,
-					"    segment bin %zu (at least %d contiguous pages free):\n",
-					i, 1 << (i - 1));
+			if (i == 0)
+				fprintf(stderr,
+						"    segment bin %zu (no contiguous free pages):\n", i);
+			else
+				fprintf(stderr,
+						"    segment bin %zu (at least %d contiguous pages free):\n",
+						i, 1 << (i - 1));
 			segment_index = area->control->segment_bins[i];
 			while (segment_index != DSA_SEGMENT_INDEX_NONE)
 			{


[parent: c0b4dad38e84]