From 442c6baac95fd5e2d1de2b4aacfdedb452e76dd8 Mon Sep 17 00:00:00 2001
From: cristianchiriac <80774326+cristianchiriac@users.noreply.github.com>
Date: Thu, 15 Oct 2026 19:40:48 +0300
Subject: [PATCH] Fix vector insert of a value that refers to an element of the
 vector

insert(position, value) and insert(position, n, value) shifted the
elements before reading value, so a value taken from the vector at or
after the insert position read the shifted element instead.

Fixes #1629
---
 include/etl/vector.h | 23 +++++++++++++++---
 test/test_vector.cpp | 57 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 77 insertions(+), 3 deletions(-)

diff --git a/include/etl/vector.h b/include/etl/vector.h
index beac6cdc..ae3bb89a 100644
--- a/include/etl/vector.h
+++ b/include/etl/vector.h
@@ -611,9 +611,18 @@ namespace etl
       }
       else
       {
+        // value may refer to an element that is about to be shifted.
+        const_pointer p_value = etl::addressof(value);
+
         create_back(back());
         etl::move_backward(position_, p_end - 2, p_end - 1);
-        *position_ = value;
+
+        if ((p_value >= position_) && (p_value < p_end))
+        {
+          ++p_value;
+        }
+
+        *position_ = *p_value;
       }
 
       return position_;
@@ -836,6 +845,14 @@ namespace etl
       size_t copy_new_n      = construct_old_n;
       size_t construct_new_n = insert_n - copy_new_n;
 
+      // value may refer to an element that is about to be shifted.
+      const_pointer p_value = etl::addressof(value);
+
+      if ((p_value >= position_) && (p_value < p_end))
+      {
+        p_value += n;
+      }
+
       // Construct old.
       etl::uninitialized_move(p_end - construct_old_n, p_end, p_construct_old);
       ETL_ADD_DEBUG_COUNT(construct_old_n);
@@ -844,11 +861,11 @@ namespace etl
       etl::move_backward(p_buffer + insert_begin, p_buffer + insert_begin + copy_old_n, p_buffer + insert_end + copy_old_n);
 
       // Construct new.
-      etl::uninitialized_fill_n(p_end, construct_new_n, value);
+      etl::uninitialized_fill_n(p_end, construct_new_n, *p_value);
       ETL_ADD_DEBUG_COUNT(construct_new_n);
 
       // Copy new.
-      etl::fill_n(p_buffer + insert_begin, copy_new_n, value);
+      etl::fill_n(p_buffer + insert_begin, copy_new_n, *p_value);
 
       p_end += n;
     }
diff --git a/test/test_vector.cpp b/test/test_vector.cpp
index 32799337..e14542c7 100644
--- a/test/test_vector.cpp
+++ b/test/test_vector.cpp
@@ -777,6 +777,33 @@ namespace
       }
     }
 
+    //*************************************************************************
+    TEST_FIXTURE(SetupFixture, test_insert_position_value_from_self)
+    {
+      const size_t INITIAL_SIZE = 5;
+
+      for (size_t offset = 0; offset <= INITIAL_SIZE; ++offset)
+      {
+        for (size_t source = 0; source < INITIAL_SIZE; ++source)
+        {
+          Compare_Data compare_data;
+          Data         data;
+
+          data.assign(initial_data.begin(), initial_data.begin() + INITIAL_SIZE);
+          compare_data.assign(initial_data.begin(), initial_data.begin() + INITIAL_SIZE);
+
+          data.insert(data.cbegin() + offset, data[source]);
+          compare_data.insert(compare_data.cbegin() + static_cast<ptrdiff_t>(offset), compare_data[source]);
+
+          CHECK_EQUAL(compare_data.size(), data.size());
+
+          bool is_equal = std::equal(data.cbegin(), data.cend(), compare_data.cbegin());
+
+          CHECK(is_equal);
+        }
+      }
+    }
+
     //*************************************************************************
     TEST_FIXTURE(SetupFixture, test_insert_position_value_outofbounds)
     {
@@ -971,6 +998,36 @@ namespace
       }
     }
 
+    //*************************************************************************
+    TEST_FIXTURE(SetupFixture, test_insert_position_n_value_from_self)
+    {
+      const size_t INITIAL_SIZE = 5;
+
+      for (size_t insert_size = 1; insert_size <= 4; ++insert_size)
+      {
+        for (size_t offset = 0; offset <= INITIAL_SIZE; ++offset)
+        {
+          for (size_t source = 0; source < INITIAL_SIZE; ++source)
+          {
+            Compare_Data compare_data;
+            Data         data;
+
+            data.assign(initial_data.begin(), initial_data.begin() + INITIAL_SIZE);
+            compare_data.assign(initial_data.begin(), initial_data.begin() + INITIAL_SIZE);
+
+            data.insert(data.cbegin() + offset, insert_size, data[source]);
+            compare_data.insert(compare_data.cbegin() + static_cast<ptrdiff_t>(offset), insert_size, compare_data[source]);
+
+            CHECK_EQUAL(compare_data.size(), data.size());
+
+            bool is_equal = std::equal(data.cbegin(), data.cend(), compare_data.cbegin());
+
+            CHECK(is_equal);
+          }
+        }
+      }
+    }
+
     //*************************************************************************
 #include "etl/private/diagnostic_uninitialized_push.h"
     TEST_FIXTURE(SetupFixture, test_insert_position_n_value_outofbounds)