From 4c96bc2dd93ae3e63e84c1164104e5d0e3a14156 Mon Sep 17 00:00:00 2001
From: Moritz Fischer <moritzf@google.com>
Date: Wed, 14 Sep 2022 11:35:39 -0700
Subject: [PATCH 1/4] sys: util: Prevent multiple definitions of ARRAY_SIZE

Prefix ARRAY_SIZE macro with an #undef ARRAY_SIZE to prevent
multiple definition issues when dealing with third party
libraries that have their own definitions.

Signed-off-by: Moritz Fischer <moritzf@google.com>
---
 include/zephyr/sys/util.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/zephyr/sys/util.h b/include/zephyr/sys/util.h
index fdc4532cf8ceae..8f0ce96b9b8e51 100644
--- a/include/zephyr/sys/util.h
+++ b/include/zephyr/sys/util.h
@@ -82,6 +82,7 @@ extern "C" {
 /* The built-in function used below for type checking in C is not
  * supported by GNU C++.
  */
+#undef ARRAY_SIZE
 #define ARRAY_SIZE(array) (sizeof(array) / sizeof((array)[0]))
 
 #else /* __cplusplus */
@@ -105,6 +106,7 @@ extern "C" {
  *
  * In C, passing a pointer as @p array causes a compile error.
  */
+#undef ARRAY_SIZE
 #define ARRAY_SIZE(array) \
 	((size_t) (IS_ARRAY(array) + (sizeof(array) / sizeof((array)[0]))))
 

From 2922060ac442747f38a5075ff4dd0bf7cc9fc070 Mon Sep 17 00:00:00 2001
From: Moritz Fischer <moritzf@google.com>
Date: Wed, 14 Sep 2022 15:46:17 -0700
Subject: [PATCH 2/4] tests: unit: Add explicit ARRAY_SIZE tests

This adds a test that explicitly (rather than implicitly)
tests the ARRAY_SIZE(x) macro.

Signed-off-by: Moritz Fischer <moritzf@google.com>
---
 tests/unit/util/main.c   | 10 ++++++++++
 tests/unit/util/test.inc |  6 ++++++
 2 files changed, 16 insertions(+)

diff --git a/tests/unit/util/main.c b/tests/unit/util/main.c
index 44f73bfb7d3b76..4a83146f6e5085 100644
--- a/tests/unit/util/main.c
+++ b/tests/unit/util/main.c
@@ -116,6 +116,11 @@ ZTEST(util_cxx, test_ARRAY_INDEX)
 	run_ARRAY_INDEX();
 }
 
+ZTEST(util_cxx, test_ARRAY_SIZE)
+{
+	run_ARRAY_SIZE();
+}
+
 ZTEST(util_cxx, test_PART_OF_ARRAY)
 {
 	run_PART_OF_ARRAY();
@@ -234,6 +239,11 @@ ZTEST(util_cc, test_ARRAY_INDEX)
 	run_ARRAY_INDEX();
 }
 
+ZTEST(util_cc, test_ARRAY_SIZE)
+{
+	run_ARRAY_SIZE();
+}
+
 ZTEST(util_cc, test_PART_OF_ARRAY)
 {
 	run_PART_OF_ARRAY();
diff --git a/tests/unit/util/test.inc b/tests/unit/util/test.inc
index 08358c87820760..e3afc5e504e729 100644
--- a/tests/unit/util/test.inc
+++ b/tests/unit/util/test.inc
@@ -526,3 +526,9 @@ void run_ARRAY_INDEX_FLOOR(void)
 
 	zassert_equal(array[ARRAY_INDEX_FLOOR(array, &alias[1])], 0);
 }
+
+void run_ARRAY_SIZE(void)
+{
+	size_t array[] = {1, 2, 3, 4};
+	zassert_equal(ARRAY_SIZE(array), 4);
+}

From 9542e34583dcde3d47bfa06fba2094058441836f Mon Sep 17 00:00:00 2001
From: Moritz Fischer <moritzf@google.com>
Date: Wed, 5 Oct 2022 09:52:31 -0700
Subject: [PATCH 3/4] sys: util: Take stronger stance on MIN()/MAX()

Instead of guarding with #ifndef against previous definitions
use a stronger stance and #undef previous definitions.

Signed-off-by: Moritz Fischer <moritzf@google.com>
---
 include/zephyr/sys/util.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/include/zephyr/sys/util.h b/include/zephyr/sys/util.h
index 8f0ce96b9b8e51..b4f60dda8977c7 100644
--- a/include/zephyr/sys/util.h
+++ b/include/zephyr/sys/util.h
@@ -239,7 +239,6 @@ extern "C" {
 #define ceiling_fraction(numerator, divider) \
 	(((numerator) + ((divider) - 1)) / (divider))
 
-#ifndef MAX
 /**
  * @brief Obtain the maximum of two values.
  *
@@ -251,10 +250,9 @@ extern "C" {
  *
  * @returns Maximum value of @p a and @p b.
  */
+#undef MAX
 #define MAX(a, b) (((a) > (b)) ? (a) : (b))
-#endif
 
-#ifndef MIN
 /**
  * @brief Obtain the minimum of two values.
  *
@@ -266,8 +264,8 @@ extern "C" {
  *
  * @returns Minimum value of @p a and @p b.
  */
+#undef MIN
 #define MIN(a, b) (((a) < (b)) ? (a) : (b))
-#endif
 
 #ifndef CLAMP
 /**

From 37cf75d0cfb7819488214ece840abae4f413dcf2 Mon Sep 17 00:00:00 2001
From: Moritz Fischer <moritzf@google.com>
Date: Wed, 5 Oct 2022 15:57:30 -0700
Subject: [PATCH 4/4] doc/release-note-3.3: Add notes about MAX/MIN/ARRAY_SIZE

Added summary of new behavior for MAX(), MIN() and ARRAY_SIZE().

Signed-off-by: Moritz Fischer <moritzf@google.com>
---
 doc/releases/release-notes-3.3.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/doc/releases/release-notes-3.3.rst b/doc/releases/release-notes-3.3.rst
index 31a28d4415149c..42da36cdb43312 100644
--- a/doc/releases/release-notes-3.3.rst
+++ b/doc/releases/release-notes-3.3.rst
@@ -28,6 +28,12 @@ Deprecated in this release
 
 Stable API changes in this release
 ==================================
+* System Utility Headers
+
+  * Prefixed :c:func:`MIN` and :c:func:`MAX` and :c:func:`ARRAY_SIZE` with `#undef` to prevent
+    accidential multiple definitions when dealing with third party libraries that bring their
+    own definitions.
+    This is a departure from previous behavior where include order of header files mattered.
 
 New APIs in this release
 ========================