From 8b0d8888e60703dd3729e750b700e889b45fbe49 Mon Sep 17 00:00:00 2001
From: Roland Reichwein <Roland.Reichwein@bmw.de>
Date: Sun, 31 May 2026 14:02:32 +0200
Subject: [PATCH] Fixed move_iterator::operator+= and operator-= return type

move_iterator::operator+= / operator-= returned by value, but RandomAccessIterator
requirements (and std::move_iterator) expect these to return move_iterator&.
Returning by value also added an unnecessary copy and could break generic code
expecting reference semantics.
---
 include/etl/iterator.h |  4 ++--
 test/test_iterator.cpp | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/include/etl/iterator.h b/include/etl/iterator.h
index b63c38c9..a990fb6c 100644
--- a/include/etl/iterator.h
+++ b/include/etl/iterator.h
@@ -576,13 +576,13 @@ namespace etl
       return move_iterator(current - n);
     }
 
-    ETL_CONSTEXPR14 move_iterator operator+=(difference_type n)
+    ETL_CONSTEXPR14 move_iterator& operator+=(difference_type n)
     {
       current += n;
       return *this;
     }
 
-    ETL_CONSTEXPR14 move_iterator operator-=(difference_type n)
+    ETL_CONSTEXPR14 move_iterator& operator-=(difference_type n)
     {
       current -= n;
       return *this;
diff --git a/test/test_iterator.cpp b/test/test_iterator.cpp
index fac7f09e..db018c40 100644
--- a/test/test_iterator.cpp
+++ b/test/test_iterator.cpp
@@ -550,6 +550,28 @@ namespace
       CHECK_EQUAL(true, mitr->valid);
     }
 
+    //*************************************************************************
+    TEST(test_move_iterator_compound_assignment_returns_reference)
+    {
+      int data[] = {10, 20, 30, 40, 50};
+
+      etl::move_iterator<int*> mitr(&data[0]);
+
+      // operator+= must return a reference to *this
+      etl::move_iterator<int*>& ref_plus = (mitr += 2);
+      CHECK_EQUAL(&mitr, &ref_plus);
+      CHECK_EQUAL(30, *mitr);
+
+      // operator-= must return a reference to *this
+      etl::move_iterator<int*>& ref_minus = (mitr -= 1);
+      CHECK_EQUAL(&mitr, &ref_minus);
+      CHECK_EQUAL(20, *mitr);
+
+      // Chaining should work
+      (mitr += 1) += 1;
+      CHECK_EQUAL(40, *mitr);
+    }
+
     //*************************************************************************
     TEST(test_move_iterator_subtraction)
     {