v2-0001-Extend-the-length-of-BackgroundWorker.bgw_library_na.patch

From b7813f94c8546356a00218cf49db67a9cf194d96 Mon Sep 17 00:00:00 2001
From: Yurii Rashkovskii <yrashk@gmail.com>
Date: Mon, 24 Apr 2023 13:39:44 +0200
Subject: [PATCH] Extend the length of BackgroundWorker.bgw_library_name.

It is currently set at BGW_MAXLEN, which is often insufficient for
absolute paths. While it may be acceptable when used in conjunction with
$libdir, this makes it tricky to use libraries that have longer paths to
them.

The use cases where this is necessary may include:

* Local test benches
* Extensions provisioned outside of standard packaging or build
  procedures
---
 doc/src/sgml/bgworker.sgml                 |  2 +-
 src/backend/postmaster/bgworker.c          |  2 +-
 src/backend/replication/logical/launcher.c |  4 ++--
 src/include/postmaster/bgworker.h          | 14 +++++++++++++-
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/doc/src/sgml/bgworker.sgml b/doc/src/sgml/bgworker.sgml
index 7ba5da27e5..9ad1146ba0 100644
--- a/doc/src/sgml/bgworker.sgml
+++ b/doc/src/sgml/bgworker.sgml
@@ -59,7 +59,7 @@ typedef struct BackgroundWorker
     int         bgw_flags;
     BgWorkerStartTime bgw_start_time;
     int         bgw_restart_time;       /* in seconds, or BGW_NEVER_RESTART */
-    char        bgw_library_name[BGW_MAXLEN];
+    char        bgw_library_name[MAXPGPATH];
     char        bgw_function_name[BGW_MAXLEN];
     Datum       bgw_main_arg;
     char        bgw_extra[BGW_EXTRALEN];
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index 0dd22b2351..ade8b38984 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -362,7 +362,7 @@ BackgroundWorkerStateChange(bool allow_new_workers)
 		ascii_safe_strlcpy(rw->rw_worker.bgw_type,
 						   slot->worker.bgw_type, BGW_MAXLEN);
 		ascii_safe_strlcpy(rw->rw_worker.bgw_library_name,
-						   slot->worker.bgw_library_name, BGW_MAXLEN);
+						   slot->worker.bgw_library_name, sizeof(slot->worker.bgw_library_name));
 		ascii_safe_strlcpy(rw->rw_worker.bgw_function_name,
 						   slot->worker.bgw_function_name, BGW_MAXLEN);
 
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 970d170e73..4f69b03cb3 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -456,7 +456,7 @@ retry:
 	bgw.bgw_flags = BGWORKER_SHMEM_ACCESS |
 		BGWORKER_BACKEND_DATABASE_CONNECTION;
 	bgw.bgw_start_time = BgWorkerStart_RecoveryFinished;
-	snprintf(bgw.bgw_library_name, BGW_MAXLEN, "postgres");
+	snprintf(bgw.bgw_library_name, sizeof(bgw.bgw_library_name), "postgres");
 
 	if (is_parallel_apply_worker)
 		snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ParallelApplyWorkerMain");
@@ -889,7 +889,7 @@ ApplyLauncherRegister(void)
 	bgw.bgw_flags = BGWORKER_SHMEM_ACCESS |
 		BGWORKER_BACKEND_DATABASE_CONNECTION;
 	bgw.bgw_start_time = BgWorkerStart_RecoveryFinished;
-	snprintf(bgw.bgw_library_name, BGW_MAXLEN, "postgres");
+	snprintf(bgw.bgw_library_name, sizeof(bgw.bgw_library_name), "postgres");
 	snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyLauncherMain");
 	snprintf(bgw.bgw_name, BGW_MAXLEN,
 			 "logical replication launcher");
diff --git a/src/include/postmaster/bgworker.h b/src/include/postmaster/bgworker.h
index 845d4498e6..0ecb0f9804 100644
--- a/src/include/postmaster/bgworker.h
+++ b/src/include/postmaster/bgworker.h
@@ -93,13 +93,25 @@ typedef struct BackgroundWorker
 	int			bgw_flags;
 	BgWorkerStartTime bgw_start_time;
 	int			bgw_restart_time;	/* in seconds, or BGW_NEVER_RESTART */
-	char		bgw_library_name[BGW_MAXLEN];
+	char		bgw_library_name[MAXPGPATH];
 	char		bgw_function_name[BGW_MAXLEN];
 	Datum		bgw_main_arg;
 	char		bgw_extra[BGW_EXTRALEN];
 	pid_t		bgw_notify_pid; /* SIGUSR1 this backend on start/stop */
 } BackgroundWorker;
 
+/*
+ * Ensure bgw_library_name's size is backwards-compatible and sensible.
+ *
+ * Before PostgreSQL 17, we used BGW_MAXLEN for bgw_library_name which was
+ * too short for some use cases, particularly, absolute paths.
+ *
+ * The assertion below ensures that the new length is at least as long as
+ * it was before.
+ */
+StaticAssertDecl(sizeof((BackgroundWorker *)NULL)->bgw_library_name >= BGW_MAXLEN,
+		"BackgroundWorker.bgw_library_name size must be at least equal to BGW_MAXLEN");
+
 typedef enum BgwHandleStatus
 {
 	BGWH_STARTED,				/* worker is running */
-- 
2.39.2 (Apple Git-143)