From c4007799057dbe3609a0925c6d6b4a59e099ce2b Mon Sep 17 00:00:00 2001
From: John Wellbelove <john.wellbelove@etlcpp.co.uk>
Date: Fri, 3 Nov 2023 18:37:25 +0100
Subject: [PATCH] #781 etl::multi_span::iterator::operator *() fails if first
 span is empty

---
 include/etl/multi_span.h | 14 +++++++++++++-
 test/test_multi_span.cpp | 31 +++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/include/etl/multi_span.h b/include/etl/multi_span.h
index 7f98865d..2838e007 100644
--- a/include/etl/multi_span.h
+++ b/include/etl/multi_span.h
@@ -173,7 +173,19 @@ namespace etl
       {
         if (p_current != p_end)
         {
-          p_value = p_current->begin();
+          while ((p_current != p_end) && p_current->empty())
+          {
+            ++p_current;
+          }
+          
+          if (p_current != p_end)
+          {
+            p_value = p_current->begin();
+          }
+          else
+          {
+            p_value = ETL_NULLPTR;
+          }
         }
       }
 
diff --git a/test/test_multi_span.cpp b/test/test_multi_span.cpp
index d59c8d75..f4a4b066 100644
--- a/test/test_multi_span.cpp
+++ b/test/test_multi_span.cpp
@@ -174,5 +174,36 @@ namespace
       ++itr;
       CHECK_EQUAL(struct_data2[2].i, itr->i);
     }
+
+    //*************************************************************************
+    TEST(test_multi_span_with_empty_spans)
+    {
+      std::vector<etl::span<Data>> span_list =
+      {
+        etl::span<Data>(),
+        etl::span<Data>(struct_data1),
+        etl::span<Data>(),
+        etl::span<Data>(struct_data2),
+        etl::span<Data>()
+      };
+
+      etl::multi_span<Data> ms_data(etl::multi_span<Data>::span_list_type(std::begin(span_list), std::end(span_list)));
+
+      etl::multi_span<Data>::iterator itr = ms_data.begin();
+
+      CHECK_EQUAL(struct_data1[0].i, (*itr).i);
+      ++itr;
+      CHECK_EQUAL(struct_data1[1].i, (*itr).i);
+      ++itr;      
+      CHECK_EQUAL(struct_data1[2].i, (*itr).i);
+      ++itr;      
+      CHECK_EQUAL(struct_data2[0].i, (*itr).i);
+      ++itr;      
+      CHECK_EQUAL(struct_data2[1].i, (*itr).i);
+      ++itr;      
+      CHECK_EQUAL(struct_data2[2].i, (*itr).i);
+      ++itr;
+      CHECK_EQUAL(ETL_NULLPTR, itr.operator->());
+    }
   };
 }