From d419bbf16f7ad933eabbf0c6ffbaa4cbcaafe377 Mon Sep 17 00:00:00 2001
From: taltenbach <92919739+taltenbach@users.noreply.github.com>
Date: Sat, 17 Jan 2026 23:04:52 +0100
Subject: [PATCH] Fix etl::as_bytes for etl::span<const T> (#1266)

A missing 'const' in the etl::as_bytes implementation was causing a
compile-time error when etl::as_bytes was called on a span of const
values.

Co-authored-by: John Wellbelove <jwellbelove@users.noreply.github.com>
---
 include/etl/span.h                | 2 +-
 test/test_span_dynamic_extent.cpp | 3 ++-
 test/test_span_fixed_extent.cpp   | 5 +++--
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/etl/span.h b/include/etl/span.h
index 8f57148f..5d03632a 100644
--- a/include/etl/span.h
+++ b/include/etl/span.h
@@ -1303,7 +1303,7 @@ namespace etl
   span<const byte, (Size == etl::dynamic_extent) ? (etl::dynamic_extent) : (Size * sizeof(T))> 
     as_bytes(span<T, Size> s) ETL_NOEXCEPT
   {
-    return span<const byte, (Size == etl::dynamic_extent) ? (etl::dynamic_extent) : (Size * sizeof(T))>(reinterpret_cast<byte*>(s.data()), s.size_bytes());
+    return span<const byte, (Size == etl::dynamic_extent) ? (etl::dynamic_extent) : (Size * sizeof(T))>(reinterpret_cast<const byte*>(s.data()), s.size_bytes());
   }
 
   //*************************************************************************
diff --git a/test/test_span_dynamic_extent.cpp b/test/test_span_dynamic_extent.cpp
index 7fc1c8c0..586eadcb 100644
--- a/test/test_span_dynamic_extent.cpp
+++ b/test/test_span_dynamic_extent.cpp
@@ -1325,8 +1325,9 @@ namespace
     TEST(test_convert_span_any_to_span_byte)
     {
       float data[2]{3.141592f, 2.71828f };
+      const float const_data[2]{3.141592f, 2.71828f };
 
-      auto const const_bytes    = etl::as_bytes(etl::span<float, etl::dynamic_extent>{data});
+      auto const const_bytes    = etl::as_bytes(etl::span<const float, etl::dynamic_extent>{const_data});
       auto const writable_bytes = etl::as_writable_bytes(etl::span<float, etl::dynamic_extent>{data});
 
       CHECK_EQUAL(const_bytes.size(),    sizeof(data));
diff --git a/test/test_span_fixed_extent.cpp b/test/test_span_fixed_extent.cpp
index 137bd9b8..a1825c2c 100644
--- a/test/test_span_fixed_extent.cpp
+++ b/test/test_span_fixed_extent.cpp
@@ -1163,12 +1163,13 @@ namespace
     TEST(test_convert_span_any_to_span_byte)
     {
       float data[2]{3.141592f, 2.71828f};
+      const float const_data[2]{3.141592f, 2.71828f};
 
 #if ETL_USING_CPP17
-      auto const const_bytes    = etl::as_bytes(etl::span{ data });
+      auto const const_bytes    = etl::as_bytes(etl::span{ const_data });
       auto const writable_bytes = etl::as_writable_bytes(etl::span{ data });
 #else
-      auto const const_bytes    = etl::as_bytes(etl::span<float, 2>(data));
+      auto const const_bytes    = etl::as_bytes(etl::span<const float, 2>(const_data));
       auto const writable_bytes = etl::as_writable_bytes(etl::span<float, 2>(data));
 #endif