From 5ee75e32fa734e8ae85ff096f1523be8e16e1b8d Mon Sep 17 00:00:00 2001
From: Andres Freund
Date: Mon, 24 Feb 2025 05:39:27 -0500
Subject: Add static asserts for MAX_BACKENDS limiting factors

So far the various dependencies were documented in the comment above
MAX_BACKENDS, but not checked.

Discussion: https://postgr.es/m/CA+COZaBO_s3LfALq=b+HcBHFSOEGiApVjrRacCe4VP9m7CJsNQ@mail.gmail.com
---
 src/backend/storage/lmgr/deadlock.c | 3 +++
 src/backend/utils/cache/inval.c     | 5 +++++
 2 files changed, 8 insertions(+)

(limited to 'src/backend')

diff --git a/src/backend/storage/lmgr/deadlock.c b/src/backend/storage/lmgr/deadlock.c
index dc6923f8132..c4bfaaa67ac 100644
--- a/src/backend/storage/lmgr/deadlock.c
+++ b/src/backend/storage/lmgr/deadlock.c
@@ -30,6 +30,7 @@
 #include "pgstat.h"
 #include "storage/lmgr.h"
 #include "storage/proc.h"
+#include "storage/procnumber.h"
 #include "utils/memutils.h"
 
 
@@ -191,6 +192,8 @@ InitDeadLockChecking(void)
 	 * last MaxBackends entries in possibleConstraints[] are reserved as
 	 * output workspace for FindLockCycle.
 	 */
+	StaticAssertStmt(MAX_BACKENDS_BITS <= (32 - 3),
+					 "MAX_BACKENDS_BITS too big for * 4");
 	maxPossibleConstraints = MaxBackends * 4;
 	possibleConstraints =
 		(EDGE *) palloc(maxPossibleConstraints * sizeof(EDGE));
diff --git a/src/backend/utils/cache/inval.c b/src/backend/utils/cache/inval.c
index 6aff1ec01d7..700ccb6df9b 100644
--- a/src/backend/utils/cache/inval.c
+++ b/src/backend/utils/cache/inval.c
@@ -120,6 +120,7 @@
 #include "catalog/catalog.h"
 #include "catalog/pg_constraint.h"
 #include "miscadmin.h"
+#include "storage/procnumber.h"
 #include "storage/sinval.h"
 #include "storage/smgr.h"
 #include "utils/catcache.h"
@@ -1651,6 +1652,10 @@ CacheInvalidateSmgr(RelFileLocatorBackend rlocator)
 {
 	SharedInvalidationMessage msg;
 
+	/* verify optimization stated above stays valid */
+	StaticAssertStmt(MAX_BACKENDS_BITS <= 23,
+					 "MAX_BACKEND_BITS is too big for inval.c");
+
 	msg.sm.id = SHAREDINVALSMGR_ID;
 	msg.sm.backend_hi = rlocator.backend >> 16;
 	msg.sm.backend_lo = rlocator.backend & 0xffff;
-- 
cgit v1.2.3