From: Peter Eisentraut <peter@eisentraut.org>
Date: Mon, 16 Mar 2026 09:41:38 +0000 (+0100)
Subject: Use C11 alignas in typedef definitions
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=5c2a8d272b9aa95f36355357095a2838120b0fe2;p=thirdparty%2Fpostgresql.git

Use C11 alignas in typedef definitions

They were already using pg_attribute_aligned.  This replaces that with
alignas and moves that into the required syntactic position.

Suggested-by: Peter Eisentraut <peter@eisentraut.org>
Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://postgr.es/m/d7a788fa-e609-4894-a8be-2f70e135424f%40eisentraut.org
---

diff --git a/src/backend/storage/aio/method_io_uring.c b/src/backend/storage/aio/method_io_uring.c
index ed6e71bcd46..4867ded35ea 100644
--- a/src/backend/storage/aio/method_io_uring.c
+++ b/src/backend/storage/aio/method_io_uring.c
@@ -79,13 +79,15 @@ const IoMethodOps pgaio_uring_ops = {
 
 /*
  * Per-backend state when using io_method=io_uring
- *
- * Align the whole struct to a cacheline boundary, to prevent false sharing
- * between completion_lock and prior backend's io_uring_ring.
  */
-typedef struct pg_attribute_aligned (PG_CACHE_LINE_SIZE)
-PgAioUringContext
+typedef struct PgAioUringContext
 {
+	/*
+	 * Align the whole struct to a cacheline boundary, to prevent false
+	 * sharing between completion_lock and prior backend's io_uring_ring.
+	 */
+	alignas(PG_CACHE_LINE_SIZE)
+
 	/*
 	 * Multiple backends can process completions for this backend's io_uring
 	 * instance (e.g. when the backend issuing IO is busy doing something
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 3f89450c216..bf3094f0f7d 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -180,6 +180,11 @@ typedef enum
  */
 typedef struct PGPROC
 {
+	/*
+	 * Align the struct at cache line boundaries.  This is just for
+	 * performance, to avoid false sharing.
+	 */
+	alignas(PG_CACHE_LINE_SIZE)
 	dlist_head *procgloballist; /* procglobal list that owns this PGPROC */
 	dlist_node	freeProcsLink;	/* link in procgloballist, when in recycled
 								 * state */
@@ -375,14 +380,6 @@ typedef struct PGPROC
 
 	uint32		wait_event_info;	/* proc's wait information */
 }
-
-/*
- * If compiler understands aligned pragma, use it to align the struct at cache
- * line boundaries.  This is just for performance, to avoid false sharing.
- */
-#if defined(pg_attribute_aligned)
-			pg_attribute_aligned(PG_CACHE_LINE_SIZE)
-#endif
 PGPROC;
 
 extern PGDLLIMPORT PGPROC *MyProc;