From d794e84c547f2486289d9900f6db04c7beddd673 Mon Sep 17 00:00:00 2001
From: mike919192 <91038685+mike919192@users.noreply.github.com>
Date: Tue, 25 Mar 2025 14:16:44 -0400
Subject: [PATCH] Potential fix for span construct (#1051)

* Try fix for span constructors

* Make base class public
---
 include/etl/span.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/etl/span.h b/include/etl/span.h
index 8d03e5fb..a313b54b 100644
--- a/include/etl/span.h
+++ b/include/etl/span.h
@@ -55,11 +55,13 @@ SOFTWARE.
 
 namespace etl
 {
+  //empty base optimization means this has zero size
+  class span_base {};
   //***************************************************************************
   /// Span - Fixed Extent
   //***************************************************************************
   template <typename T, size_t Extent = etl::dynamic_extent>
-  class span
+  class span : public span_base
   {
   public:
 
@@ -113,7 +115,8 @@ namespace etl
     /// Construct from a container or other type that supports
     /// data() and size() member functions.
     //*************************************************************************
-    template <typename TContainer, typename = typename etl::enable_if<!etl::is_pointer<etl::remove_reference_t<TContainer>>::value &&
+    template <typename TContainer, typename = typename etl::enable_if<!etl::is_base_of<span_base, etl::remove_reference_t<TContainer>>::value &&
+                                                                      !etl::is_pointer<etl::remove_reference_t<TContainer>>::value &&
                                                                       !etl::is_array<etl::remove_reference_t<TContainer>>::value&&
                                                                       etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<typename etl::remove_reference_t<TContainer>::value_type>>::value, void>::type>
       ETL_CONSTEXPR span(TContainer&& a) ETL_NOEXCEPT
@@ -158,7 +161,7 @@ namespace etl
     /// Copy constructor
     //*************************************************************************
     template <typename U, size_t N>
-    ETL_CONSTEXPR span(const etl::span<U, N>& other, typename etl::enable_if<(Extent == etl::dynamic_extent) || (N == etl::dynamic_extent) || (N == Extent), void>::type) ETL_NOEXCEPT
+    ETL_CONSTEXPR span(const etl::span<U, N>& other, typename etl::enable_if<(Extent == etl::dynamic_extent) || (N == etl::dynamic_extent) || (N == Extent), void>::type* = 0) ETL_NOEXCEPT
       : pbegin(other.data())
     {
     }
@@ -511,7 +514,8 @@ namespace etl
     /// Construct from a container or other type that supports
     /// data() and size() member functions.
     //*************************************************************************
-    template <typename TContainer, typename = typename etl::enable_if<!etl::is_pointer<etl::remove_reference_t<TContainer>>::value &&
+    template <typename TContainer, typename = typename etl::enable_if<!etl::is_base_of<span_base, etl::remove_reference_t<TContainer>>::value &&
+                                                                      !etl::is_pointer<etl::remove_reference_t<TContainer>>::value &&
                                                                       !etl::is_array<etl::remove_reference_t<TContainer>>::value &&
                                                                       etl::is_same<etl::remove_cv_t<T>, etl::remove_cv_t<typename etl::remove_reference_t<TContainer>::value_type>>::value, void>::type>
       ETL_CONSTEXPR span(TContainer&& a) ETL_NOEXCEPT