From: Maxime Henrion <mhenrion@haproxy.com>
Date: Tue, 9 Dec 2025 15:51:33 +0000 (-0500)
Subject: CLEANUP: improvements to the alignment macros
X-Git-Tag: v3.4-dev1~5
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=74719dc4577e8e723200e7a1c39da9ae522c0654;p=thirdparty%2Fhaproxy.git

CLEANUP: improvements to the alignment macros

- It is now possible to use the THREAD_ALIGN and THREAD_ALIGNED macros
  without a parameter. In this case, we automatically align on the cache
  line size.
- The cache line size is set to 64 by default to match the current code,
  but it can be overridden on the command line.
- This required moving the DEFVAL/DEFNULL/DEFZERO macros to compiler.h
  instead of tools-t.h, to avoid namespace pollution if we included
  tools-t.h from compiler.h.
---

diff --git a/include/haproxy/compiler.h b/include/haproxy/compiler.h
index b5b3b083e..f37d473e2 100644
--- a/include/haproxy/compiler.h
+++ b/include/haproxy/compiler.h
@@ -31,6 +31,23 @@
 #include <stdlib.h>
 #endif
 
+/* DEFVAL() returns either the second argument as-is, or <def> if absent. This
+ * is for use in macros arguments.
+ */
+#define DEFVAL(_def,...) _FIRST_ARG(NULL, ##__VA_ARGS__, (_def))
+
+/* DEFNULL() returns either the argument as-is, or NULL if absent. This is for
+ * use in macros arguments.
+ */
+#define DEFNULL(...) DEFVAL(NULL, ##__VA_ARGS__)
+
+/* DEFZERO() returns either the argument as-is, or 0 if absent. This is for
+ * use in macros arguments.
+ */
+#define DEFZERO(...) DEFVAL(0, ##__VA_ARGS__)
+
+#define _FIRST_ARG(a, b, ...) b
+
 /*
  * Gcc before 3.0 needs [0] to declare a variable-size array
  */
@@ -415,6 +432,13 @@
  * for multi_threading, see THREAD_PAD() below.                              *
 \*****************************************************************************/
 
+/* Cache line size for alignment purposes. This value is incorrect for some
+ * Apple CPUs which have 128 bytes cache lines.
+ */
+#ifndef CACHELINE_SIZE
+#define CACHELINE_SIZE 64
+#endif
+
 /* sets alignment for current field or variable */
 #ifndef ALIGNED
 #define ALIGNED(x) __attribute__((aligned(x)))
@@ -438,12 +462,12 @@
 #endif
 #endif
 
-/* sets alignment for current field or variable only when threads are enabled.
- * Typically used to respect cache line alignment to avoid false sharing.
+/* Sets alignment for current field or variable only when threads are enabled.
+ * When no parameters are provided, we align to the cache line size.
  */
 #ifndef THREAD_ALIGNED
 #ifdef USE_THREAD
-#define THREAD_ALIGNED(x) __attribute__((aligned(x)))
+#define THREAD_ALIGNED(...) ALIGNED(DEFVAL(CACHELINE_SIZE, ##__VA_ARGS__))
 #else
 #define THREAD_ALIGNED(x)
 #endif
@@ -476,13 +500,12 @@
 #endif
 #endif
 
-/* add an optional alignment for next fields in a structure, only when threads
- * are enabled. Typically used to respect cache line alignment to avoid false
- * sharing.
+/* Add an optional alignment for next fields in a structure, only when threads
+ * are enabled. When no parameters are provided, we align to the cache line size.
  */
 #ifndef THREAD_ALIGN
 #ifdef USE_THREAD
-#define THREAD_ALIGN(x) union { } ALIGNED(x)
+#define THREAD_ALIGN(...) union { } ALIGNED(DEFVAL(CACHELINE_SIZE, ##__VA_ARGS__))
 #else
 #define THREAD_ALIGN(x)
 #endif
diff --git a/include/haproxy/tools-t.h b/include/haproxy/tools-t.h
index ef3e136a4..77911dd85 100644
--- a/include/haproxy/tools-t.h
+++ b/include/haproxy/tools-t.h
@@ -47,23 +47,6 @@
 /* return the largest possible integer of type <ret>, with all bits set */
 #define MAX_RANGE(ret) (~(typeof(ret))0)
 
-/* DEFVAL() returns either the second argument as-is, or <def> if absent. This
- * is for use in macros arguments.
- */
-#define DEFVAL(_def,...) _FIRST_ARG(NULL, ##__VA_ARGS__, (_def))
-
-/* DEFNULL() returns either the argument as-is, or NULL if absent. This is for
- * use in macros arguments.
- */
-#define DEFNULL(...) DEFVAL(NULL, ##__VA_ARGS__)
-
-/* DEFZERO() returns either the argument as-is, or 0 if absent. This is for
- * use in macros arguments.
- */
-#define DEFZERO(...) DEFVAL(0, ##__VA_ARGS__)
-
-#define _FIRST_ARG(a, b, ...) b
-
 /* options flags for parse_line() */
 #define PARSE_OPT_SHARP         0x00000001      // '#' ends the line
 #define PARSE_OPT_BKSLASH       0x00000002      // '\' escapes chars