diff --git a/arduino/library-arduino.json b/arduino/library-arduino.json
index 5448d465..73eb0722 100644
--- a/arduino/library-arduino.json
+++ b/arduino/library-arduino.json
@@ -1,6 +1,6 @@
 {
   "name": "Embedded Template Library - Arduino",
-  "version": "20.31.0",
+  "version": "20.31.1",
   "authors": {
     "name": "John Wellbelove",
     "email": "john.wellbelove@etlcpp.com"
diff --git a/arduino/library-arduino.properties b/arduino/library-arduino.properties
index 18864967..5a2fcd0d 100644
--- a/arduino/library-arduino.properties
+++ b/arduino/library-arduino.properties
@@ -1,5 +1,5 @@
 name=Embedded Template Library - Arduino
-version=20.31.0
+version=20.31.1
 author= John Wellbelove <john.wellbelove@etlcpp.com>
 maintainer=John Wellbelove <john.wellbelove@etlcpp.com>
 license=MIT
diff --git a/include/etl/poly_span.h b/include/etl/poly_span.h
index 50f31ba3..e36670da 100644
--- a/include/etl/poly_span.h
+++ b/include/etl/poly_span.h
@@ -511,7 +511,7 @@ namespace etl
     /// Obtains a poly_span that is a view over the first COUNT elements of this poly_span.
     //*************************************************************************
     template <size_t COUNT>
-    ETL_CONSTEXPR etl::poly_span<element_type, COUNT> first() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, COUNT> first() const ETL_NOEXCEPT
     {
       return etl::poly_span<element_type, COUNT>(pbegin, 0U, COUNT, element_size);
     }
@@ -519,7 +519,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a poly_span that is a view over the first count elements of this poly_span.
     //*************************************************************************
-    ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> first(size_t count) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> first(size_t count) const
     {
       return etl::poly_span<element_type, etl::dynamic_extent>(pbegin, 0U, count, element_size);
     }
@@ -528,7 +528,7 @@ namespace etl
     /// Obtains a poly_span that is a view over the last COUNT elements of this poly_span.
     //*************************************************************************
     template <size_t COUNT>
-    ETL_CONSTEXPR etl::poly_span<element_type, COUNT> last() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, COUNT> last() const ETL_NOEXCEPT
     {
       return etl::poly_span<element_type, COUNT>(pbegin, Extent - COUNT, COUNT, element_size);
     }
@@ -536,7 +536,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a poly_span that is a view over the last count elements of this poly_span.
     //*************************************************************************
-    ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> last(size_t count) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> last(size_t count) const ETL_NOEXCEPT
     {
       return etl::poly_span<element_type, etl::dynamic_extent>(pbegin, Extent - count, count, element_size);
     }
@@ -546,7 +546,7 @@ namespace etl
     /// Obtains a poly_span that is a view from OFFSET over the next COUNT elements of this poly_span.
     //*************************************************************************
     template <const size_t OFFSET, size_t COUNT = etl::dynamic_extent>
-    ETL_CONSTEXPR etl::poly_span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET> subspan() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET> subspan() const ETL_NOEXCEPT
     {
       return (COUNT == etl::dynamic_extent) ? etl::poly_span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET>(pbegin, OFFSET, Extent, element_size)
                                             : etl::poly_span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET>(pbegin, OFFSET, COUNT, element_size);
@@ -572,7 +572,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a poly_span that is a view from 'offset' over the next 'count' elements of this poly_span.
     //*************************************************************************
-    ETL_CONSTEXPR14 etl::poly_span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const ETL_NOEXCEPT
     {
       return (count == etl::dynamic_extent) ? etl::poly_span<element_type, etl::dynamic_extent>(pbegin, offset, Extent, element_size)
                                             : etl::poly_span<element_type, etl::dynamic_extent>(pbegin, offset, count, element_size);
@@ -640,8 +640,8 @@ namespace etl
     //*************************************************************************
     ETL_CONSTEXPR poly_span() ETL_NOEXCEPT
       : pbegin(ETL_NULLPTR)
-      , span_extent(0U)
       , element_size(0U)
+      , span_extent(0U)
     {
     }
 
@@ -744,8 +744,8 @@ namespace etl
     //*************************************************************************
     ETL_CONSTEXPR poly_span(const poly_span<TBase, etl::dynamic_extent>& other) ETL_NOEXCEPT
       : pbegin(other.pbegin)
-      , span_extent(other.span_extent)
       , element_size(other.element_size)
+      , span_extent(other.span_extent)
     {
     }
 
@@ -755,8 +755,8 @@ namespace etl
     template <typename UBase>
     ETL_CONSTEXPR poly_span(const poly_span<UBase, etl::dynamic_extent>& other) ETL_NOEXCEPT
       : pbegin(other.pbegin)
-      , span_extent(other.span_extent)
       , element_size(other.element_size)
+      , span_extent(other.span_extent)
     {
     }
 
@@ -854,8 +854,8 @@ namespace etl
     ETL_CONSTEXPR14 poly_span& operator =(const poly_span& other) ETL_NOEXCEPT
     {
       pbegin = other.pbegin;
-      span_extent = other.span_extent;
       element_size = other.element_size;
+      span_extent = other.span_extent;
       return *this;
     }
 
@@ -866,8 +866,8 @@ namespace etl
     ETL_CONSTEXPR14 poly_span& operator =(const poly_span<UBase, etl::dynamic_extent>& other) ETL_NOEXCEPT
     {
       pbegin = other.pbegin;
-      span_extent = other.span_extent;
       element_size = other.element_size;
+      span_extent = other.span_extent;
       return *this;
     }
 
@@ -883,7 +883,7 @@ namespace etl
     /// Obtains a poly_span that is a view over the first COUNT elements of this poly_span.
     //*************************************************************************
     template <size_t COUNT>
-    ETL_CONSTEXPR etl::poly_span<element_type, COUNT> first() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, COUNT> first() const ETL_NOEXCEPT
     {
       return etl::poly_span<element_type, COUNT>(pbegin, 0U, COUNT, element_size);
     }
@@ -891,7 +891,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a poly_span that is a view over the first count elements of this poly_span.
     //*************************************************************************
-    ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> first(size_t count) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> first(size_t count) const ETL_NOEXCEPT
     {
       return etl::poly_span<element_type, etl::dynamic_extent>(pbegin, 0U, count, element_size);
     }
@@ -900,7 +900,7 @@ namespace etl
     /// Obtains a poly_span that is a view over the last COUNT elements of this poly_span.
     //*************************************************************************
     template <size_t COUNT>
-    ETL_CONSTEXPR etl::poly_span<element_type, COUNT> last() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, COUNT> last() const ETL_NOEXCEPT
     {
       return etl::poly_span<element_type, COUNT>(pbegin, span_extent - COUNT, COUNT, element_size);
     }
@@ -908,7 +908,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a poly_span that is a view over the last count elements of this poly_span.
     //*************************************************************************
-    ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> last(size_t count) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> last(size_t count) const ETL_NOEXCEPT
     {
       return etl::poly_span<element_type, etl::dynamic_extent>(pbegin, span_extent - count, count, element_size);
     }
@@ -918,7 +918,7 @@ namespace etl
     /// Obtains a poly_span that is a view from OFFSET over the next COUNT elements of this poly_span.
     //*************************************************************************
     template <const size_t OFFSET, size_t COUNT = etl::dynamic_extent>
-    ETL_CONSTEXPR etl::poly_span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent> subspan() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent> subspan() const ETL_NOEXCEPT
     {
       return (COUNT == etl::dynamic_extent) ? etl::poly_span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent>(pbegin, OFFSET, span_extent, element_size)
                                             : etl::poly_span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent>(pbegin, OFFSET, COUNT, element_size);
@@ -944,7 +944,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a poly_span that is a view from 'offset' over the next 'count' elements of this poly_span.
     //*************************************************************************
-    ETL_CONSTEXPR14 etl::poly_span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::poly_span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const ETL_NOEXCEPT
     {
       return (count == etl::dynamic_extent) ? etl::poly_span<element_type, etl::dynamic_extent>(pbegin, offset, span_extent - offset, element_size)
                                             : etl::poly_span<element_type, etl::dynamic_extent>(pbegin, offset, count, element_size);
@@ -957,8 +957,8 @@ protected:
   //*************************************************************************
   ETL_CONSTEXPR poly_span(TBase* pbegin_, size_t offset_, size_t extent_, size_t element_size_) ETL_NOEXCEPT
     : pbegin(reinterpret_cast<pointer>(reinterpret_cast<char_ptr_t>(pbegin_) + (offset_ * element_size_)))
-    , span_extent(extent_)
     , element_size(element_size_)
+    , span_extent(extent_)
   {
   }
 
@@ -981,8 +981,8 @@ protected:
     }
 
     pointer pbegin;
-    size_t  span_extent;
     size_t  element_size;
+    size_t  span_extent;
   };
 
   //*************************************************************************
diff --git a/include/etl/span.h b/include/etl/span.h
index efc66f6c..bc6b4aa1 100644
--- a/include/etl/span.h
+++ b/include/etl/span.h
@@ -216,7 +216,7 @@ namespace etl
     //*************************************************************************
     /// Returns a reference to the first element.
     //*************************************************************************
-    ETL_CONSTEXPR reference front() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR reference front() const ETL_NOEXCEPT
     {
       return *pbegin;
     }
@@ -224,7 +224,7 @@ namespace etl
     //*************************************************************************
     /// Returns a reference to the last element.
     //*************************************************************************
-    ETL_CONSTEXPR reference back() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR reference back() const ETL_NOEXCEPT
     {
       return *((pbegin + Extent) - 1);
     }
@@ -232,7 +232,7 @@ namespace etl
     //*************************************************************************
     /// Returns a pointer to the first element of the internal storage.
     //*************************************************************************
-    ETL_CONSTEXPR pointer data() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR pointer data() const ETL_NOEXCEPT
     {
       return pbegin;
     }
@@ -240,7 +240,7 @@ namespace etl
     //*************************************************************************
     /// Returns an iterator to the beginning of the span.
     //*************************************************************************
-    ETL_CONSTEXPR iterator begin() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR iterator begin() const ETL_NOEXCEPT
     {
       return pbegin;
     }
@@ -248,7 +248,7 @@ namespace etl
     //*************************************************************************
     /// Returns an iterator to the end of the span.
     //*************************************************************************
-    ETL_CONSTEXPR iterator end() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR iterator end() const ETL_NOEXCEPT
     {
       return (pbegin + Extent);
     }
@@ -256,7 +256,7 @@ namespace etl
     //*************************************************************************
     // Returns an reverse iterator to the reverse beginning of the span.
     //*************************************************************************
-    ETL_CONSTEXPR reverse_iterator rbegin() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR reverse_iterator rbegin() const ETL_NOEXCEPT
     {
       return reverse_iterator((pbegin + Extent));
     }
@@ -264,7 +264,7 @@ namespace etl
     //*************************************************************************
     /// Returns a reverse iterator to the end of the span.
     //*************************************************************************
-    ETL_CONSTEXPR reverse_iterator rend() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR reverse_iterator rend() const ETL_NOEXCEPT
     {
       return reverse_iterator(pbegin);
     }
@@ -272,7 +272,7 @@ namespace etl
     //*************************************************************************
     /// Returns <b>true</b> if the span size is zero.
     //*************************************************************************
-    ETL_CONSTEXPR bool empty() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR bool empty() const ETL_NOEXCEPT
     {
       return false;
     }
@@ -280,7 +280,7 @@ namespace etl
     //*************************************************************************
     /// Returns the size of the span.
     //*************************************************************************
-    ETL_CONSTEXPR size_t size() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR size_t size() const ETL_NOEXCEPT
     {
       return Extent;
     }
@@ -288,7 +288,7 @@ namespace etl
     //*************************************************************************
     /// Returns the size of the span in bytes.
     //*************************************************************************
-    ETL_CONSTEXPR size_t size_bytes() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR size_t size_bytes() const ETL_NOEXCEPT
     {
       return sizeof(element_type) * Extent;
     }
@@ -296,7 +296,7 @@ namespace etl
     //*************************************************************************
     /// Returns the maximum possible size of the span.
     //*************************************************************************
-    ETL_CONSTEXPR size_t max_size() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR size_t max_size() const ETL_NOEXCEPT
     {
       return size();
     }
@@ -322,7 +322,7 @@ namespace etl
     /// Obtains a span that is a view over the first COUNT elements of this span.
     //*************************************************************************
     template <size_t COUNT>
-    ETL_CONSTEXPR etl::span<element_type, COUNT> first() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> first() const ETL_NOEXCEPT
     {
       return etl::span<element_type, COUNT>(pbegin, pbegin + COUNT);
     }
@@ -330,7 +330,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a span that is a view over the first count elements of this span.
     //*************************************************************************
-    ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> first(size_t count) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> first(size_t count) const ETL_NOEXCEPT
     {
       return etl::span<element_type, etl::dynamic_extent>(pbegin, pbegin + count);
     }
@@ -339,7 +339,7 @@ namespace etl
     /// Obtains a span that is a view over the last COUNT elements of this span.
     //*************************************************************************
     template <size_t COUNT>
-    ETL_CONSTEXPR etl::span<element_type, COUNT> last() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> last() const ETL_NOEXCEPT
     {
       return etl::span<element_type, COUNT>(pbegin + Extent - COUNT, (pbegin + Extent));
     }
@@ -347,7 +347,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a span that is a view over the last count elements of this span.
     //*************************************************************************
-    ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> last(size_t count) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> last(size_t count) const ETL_NOEXCEPT
     {
       return etl::span<element_type, etl::dynamic_extent>((pbegin + Extent) - count, (pbegin + Extent));
     }
@@ -357,8 +357,8 @@ namespace etl
     /// Obtains a span that is a view from OFFSET over the next COUNT elements of this span.
     //*************************************************************************
     template <const size_t OFFSET, size_t COUNT = etl::dynamic_extent>
-    ETL_CONSTEXPR 
-    etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET> subspan() const
+    ETL_NODISCARD ETL_CONSTEXPR
+    etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET> subspan() const ETL_NOEXCEPT
     {
       return (COUNT == etl::dynamic_extent) ? etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET>(pbegin + OFFSET, (pbegin + Extent))
                                             : etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : Extent - OFFSET>(pbegin + OFFSET, pbegin + OFFSET + COUNT);
@@ -384,7 +384,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a span that is a view from 'offset' over the next 'count' elements of this span.
     //*************************************************************************
-    ETL_CONSTEXPR14 etl::span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const ETL_NOEXCEPT
     {
       return (count == etl::dynamic_extent) ? etl::span<element_type, etl::dynamic_extent>(pbegin + offset, (pbegin + Extent))
                                             : etl::span<element_type, etl::dynamic_extent>(pbegin + offset, pbegin + offset + count);
@@ -573,7 +573,7 @@ namespace etl
     //*************************************************************************
     /// Returns a reference to the first element.
     //*************************************************************************
-    ETL_CONSTEXPR reference front() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR reference front() const ETL_NOEXCEPT
     {
       return *pbegin;
     }
@@ -581,7 +581,7 @@ namespace etl
     //*************************************************************************
     /// Returns a reference to the last element.
     //*************************************************************************
-    ETL_CONSTEXPR reference back() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR reference back() const ETL_NOEXCEPT
     {
       return *(pend - 1);
     }
@@ -589,7 +589,7 @@ namespace etl
     //*************************************************************************
     /// Returns a pointer to the first element of the internal storage.
     //*************************************************************************
-    ETL_CONSTEXPR pointer data() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR pointer data() const ETL_NOEXCEPT
     {
       return pbegin;
     }
@@ -597,7 +597,7 @@ namespace etl
     //*************************************************************************
     /// Returns an iterator to the beginning of the span.
     //*************************************************************************
-    ETL_CONSTEXPR iterator begin() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR iterator begin() const ETL_NOEXCEPT
     {
       return pbegin;
     }
@@ -605,7 +605,7 @@ namespace etl
     //*************************************************************************
     /// Returns an iterator to the end of the span.
     //*************************************************************************
-    ETL_CONSTEXPR iterator end() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR iterator end() const ETL_NOEXCEPT
     {
       return pend;
     }
@@ -613,7 +613,7 @@ namespace etl
     //*************************************************************************
     // Returns an reverse iterator to the reverse beginning of the span.
     //*************************************************************************
-    ETL_CONSTEXPR reverse_iterator rbegin() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR reverse_iterator rbegin() const ETL_NOEXCEPT
     {
       return reverse_iterator(pend);
     }
@@ -621,7 +621,7 @@ namespace etl
     //*************************************************************************
     /// Returns a reverse iterator to the end of the span.
     //*************************************************************************
-    ETL_CONSTEXPR reverse_iterator rend() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR reverse_iterator rend() const ETL_NOEXCEPT
     {
       return reverse_iterator(pbegin);
     }
@@ -629,7 +629,7 @@ namespace etl
     //*************************************************************************
     /// Returns <b>true</b> if the span size is zero.
     //*************************************************************************
-    ETL_CONSTEXPR bool empty() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR bool empty() const ETL_NOEXCEPT
     {
       return (pbegin == pend);
     }
@@ -637,7 +637,7 @@ namespace etl
     //*************************************************************************
     /// Returns the size of the span.
     //*************************************************************************
-    ETL_CONSTEXPR size_t size() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR size_t size() const ETL_NOEXCEPT
     {
       return (pend - pbegin);
     }
@@ -645,7 +645,7 @@ namespace etl
     //*************************************************************************
     /// Returns the size of the span in bytes.
     //*************************************************************************
-    ETL_CONSTEXPR size_t size_bytes() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR size_t size_bytes() const ETL_NOEXCEPT
     {
       return sizeof(element_type) * (pend - pbegin);
     }
@@ -653,7 +653,7 @@ namespace etl
     //*************************************************************************
     /// Returns the maximum possible size of the span.
     //*************************************************************************
-    ETL_CONSTEXPR size_t max_size() const ETL_NOEXCEPT
+    ETL_NODISCARD ETL_CONSTEXPR size_t max_size() const ETL_NOEXCEPT
     {
       return size();
     }
@@ -680,7 +680,7 @@ namespace etl
     /// Obtains a span that is a view over the first COUNT elements of this span.
     //*************************************************************************
     template <size_t COUNT>
-    ETL_CONSTEXPR etl::span<element_type, COUNT> first() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> first() const ETL_NOEXCEPT
     {
       return etl::span<element_type, COUNT>(pbegin, pbegin + COUNT);
     }
@@ -688,7 +688,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a span that is a view over the first count elements of this span.
     //*************************************************************************
-    ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> first(size_t count) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> first(size_t count) const ETL_NOEXCEPT
     {
       return etl::span<element_type, etl::dynamic_extent>(pbegin, pbegin + count);
     }
@@ -697,7 +697,7 @@ namespace etl
     /// Obtains a span that is a view over the last COUNT elements of this span.
     //*************************************************************************
     template <size_t COUNT>
-    ETL_CONSTEXPR etl::span<element_type, COUNT> last() const
+    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, COUNT> last() const ETL_NOEXCEPT
     {
       return etl::span<element_type, COUNT>(pend - COUNT, pend);
     }
@@ -705,7 +705,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a span that is a view over the last count elements of this span.
     //*************************************************************************
-    ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> last(size_t count) const
+    ETL_NODISCARD ETL_CONSTEXPR etl::span<element_type, etl::dynamic_extent> last(size_t count) const ETL_NOEXCEPT
     {
       return etl::span<element_type, etl::dynamic_extent>(pend - count, pend);
     }
@@ -715,8 +715,8 @@ namespace etl
     /// Obtains a span that is a view from OFFSET over the next COUNT elements of this span.
     //*************************************************************************
     template <const size_t OFFSET, size_t COUNT = etl::dynamic_extent>
-    ETL_CONSTEXPR 
-    etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent> subspan() const
+    ETL_NODISCARD ETL_CONSTEXPR
+    etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent> subspan() const ETL_NOEXCEPT
     {
       return (COUNT == etl::dynamic_extent) ? etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent>(pbegin + OFFSET, pend)
                                             : etl::span<element_type, COUNT != etl::dynamic_extent ? COUNT : etl::dynamic_extent>(pbegin + OFFSET, pbegin + OFFSET + COUNT);
@@ -742,7 +742,7 @@ namespace etl
     //*************************************************************************
     /// Obtains a span that is a view from 'offset' over the next 'count' elements of this span.
     //*************************************************************************
-    ETL_CONSTEXPR14 etl::span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const
+    ETL_NODISCARD ETL_CONSTEXPR14 etl::span<element_type, etl::dynamic_extent> subspan(size_t offset, size_t count = etl::dynamic_extent) const ETL_NOEXCEPT
     {
       return (count == etl::dynamic_extent) ? etl::span<element_type, etl::dynamic_extent>(pbegin + offset, pend)
                                             : etl::span<element_type, etl::dynamic_extent>(pbegin + offset, pbegin + offset + count);
diff --git a/include/etl/version.h b/include/etl/version.h
index e8d5a651..52ff77e0 100644
--- a/include/etl/version.h
+++ b/include/etl/version.h
@@ -40,7 +40,7 @@ SOFTWARE.
 
 #define ETL_VERSION_MAJOR 20
 #define ETL_VERSION_MINOR 31
-#define ETL_VERSION_PATCH 0
+#define ETL_VERSION_PATCH 1
 
 #define ETL_VERSION       ETL_STRING(ETL_VERSION_MAJOR) "." ETL_STRING(ETL_VERSION_MINOR) "." ETL_STRING(ETL_VERSION_PATCH)
 #define ETL_VERSION_W     ETL_WIDE_STRING(ETL_VERSION_MAJOR) L"." ETL_WIDE_STRING(ETL_VERSION_MINOR) L"." ETL_WIDE_STRING(ETL_VERSION_PATCH)
diff --git a/library.json b/library.json
index 096f3e32..9c724986 100644
--- a/library.json
+++ b/library.json
@@ -1,6 +1,6 @@
 {
   "name": "Embedded Template Library",
-  "version": "20.31.0",
+  "version": "20.31.1",
   "authors": {
     "name": "John Wellbelove",
     "email": "john.wellbelove@etlcpp.com"
diff --git a/library.properties b/library.properties
index ac230c24..3b2fa310 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=Embedded Template Library
-version=20.31.0
+version=20.31.1
 author= John Wellbelove <john.wellbelove@etlcpp.com>
 maintainer=John Wellbelove <john.wellbelove@etlcpp.com>
 license=MIT
diff --git a/subprojects/unittest-cpp.wrap b/subprojects/unittest-cpp.wrap
deleted file mode 100644
index dfdc9d8f..00000000
--- a/subprojects/unittest-cpp.wrap
+++ /dev/null
@@ -1,9 +0,0 @@
-[wrap-file]
-directory = unittest-cpp-2.0.0
-source_url = https://github.com/unittest-cpp/unittest-cpp/archive/v2.0.0.zip
-source_filename = unittest-cpp-2.0.0.zip
-source_hash = 3ba4f8b6c6e75ca8c79dd6008c78e95fb08554fbf2e0f1195fb78a4bf5a8a805
-patch_url = https://wrapdb.mesonbuild.com/v2/unittest-cpp_2.0.0-1/get_patch
-patch_filename = unittest-cpp-2.0.0-1-wrap.zip
-patch_hash = a887de2b619c13fc4fd8bff844ca7015a2046dc613ae0765dd4452ff70db12ca
-
diff --git a/support/Release notes.txt b/support/Release notes.txt
index 28d946d5..8fc61e0a 100644
--- a/support/Release notes.txt	
+++ b/support/Release notes.txt	
@@ -1,3 +1,8 @@
+===============================================================================
+20.31.1
+Addition of extra ETL_NODISCARD and ETL_NOEXCEPT to etl::span & etl::poly_span.
+Fixed warnings for initialisation order for some etl::poly_span constructors.
+
 ===============================================================================
 20.31.0
 Added etl::poly_span
diff --git a/temp/.gitignore b/temp/.gitignore
deleted file mode 100644
index 8e1feeee..00000000
--- a/temp/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-/Containers - Supporting rvalue references.txt
diff --git a/temp/fsm-patch.txt b/temp/fsm-patch.txt
deleted file mode 100644
index 0fbafd94..00000000
--- a/temp/fsm-patch.txt
+++ /dev/null
@@ -1,21 +0,0 @@
-From 18713df17b39ef01707a5891f1d26b39b74ca8a3 Mon Sep 17 00:00:00 2001
-From: =?UTF-8?q?Micha=C5=82=20Chodzikiewicz?= <mchodzikiewicz@gmail.com>
-Date: Mon, 30 Nov 2020 17:06:02 +0100
-Subject: [PATCH] Add assertion for fsm's state array order
----
- include/etl/fsm.h | 1 +
- 1 file changed, 1 insertion(+)
-diff --git a/include/etl/fsm.h b/include/etl/fsm.h
-index 84bb34c..55a41f7 100644
---- a/include/etl/fsm.h
-+++ b/include/etl/fsm.h
-@@ -230,6 +230,7 @@ namespace etl
-       for (etl::fsm_state_id_t i = 0; i < size; ++i)
-       {
-         ETL_ASSERT((state_list[i] != nullptr), ETL_ERROR(etl::fsm_null_state_exception));
-+        ETL_ASSERT((state_list[i]->state_id == i),"State list is in incorrect order");
-         state_list[i]->set_fsm_context(*this);
-       }
-     }
--- 
-2.29.2
\ No newline at end of file
diff --git a/version.txt b/version.txt
index 20f49c4f..7203c284 100644
--- a/version.txt
+++ b/version.txt
@@ -1 +1 @@
-20.31.0
+20.31.1