From: Daniel Garcia-Sanchez <daniel.garcia-sanchez@insp.upmc.fr>
Date: Mon, 26 Sep 2022 17:16:02 +0000 (+0200)
Subject: Do not dereference cend
X-Git-Tag: v9.5.0-rc1~922^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=26eeb909bfbd73aa352103a054a409a93334ba23;p=dealii.git

Do not dereference cend

Avoid deferencing cend because it is undefined behaviour.
https://en.cppreference.com/w/cpp/container/vector/end
---

diff --git a/include/deal.II/base/utilities.h b/include/deal.II/base/utilities.h
index dab4066dad..519add5db3 100644
--- a/include/deal.II/base/utilities.h
+++ b/include/deal.II/base/utilities.h
@@ -1252,7 +1252,10 @@ namespace Utilities
       const std::vector<char>::const_iterator &cend,
       std::vector<T> &                         object)
     {
-      // First get the size of the vector, and resize the output object
+      // The size of the object vector can be found in cbegin of the buffer.
+      // The data starts at cbegin + sizeof(vector_size).
+
+      // Get the size of the vector
       typename std::vector<T>::size_type vector_size;
       memcpy(&vector_size, &*cbegin, sizeof(vector_size));
 
@@ -1262,13 +1265,15 @@ namespace Utilities
              ExcMessage("The given buffer has the wrong size."));
       (void)cend;
 
-      // Then copy the elements:
+      // Copy the elements:
       object.clear();
       if (vector_size > 0)
-        object.insert(object.end(),
-                      reinterpret_cast<const T *>(&*cbegin +
-                                                  sizeof(vector_size)),
-                      reinterpret_cast<const T *>(&*cend));
+        {
+          const auto buffer_data_begin =
+            reinterpret_cast<const T *>(&*cbegin + sizeof(vector_size));
+          const auto buffer_data_end = buffer_data_begin + vector_size;
+          object.insert(object.end(), buffer_data_begin, buffer_data_end);
+        }
     }