From a938086e416639152f8da486ab21b0731cf05700 Mon Sep 17 00:00:00 2001
From: Loic Gouarin <loic.gouarin@gmail.com>
Date: Thu, 29 Oct 2026 18:56:52 +0100
Subject: [PATCH] Return a value from xoptional_assembly_storage::data()

Both data() overloads had the statement pointer(front()); with no
return. C++ parses that line as the declaration of a local function
named front, which is what GCC's -Wparentheses and -Wshadow pointed
at. Each overload then fell off the end of a function returning a
value:

- calling one overload is undefined behavior. With GCC 15 at -O2,
  stor.data()->value() segfaults.
- calling both in one translation unit does not compile, because the
  two local declarations of xt::front have different return types.

Return the closure pointer to the front element, and add a test for
the mutable and const overloads.
---
 .../optional/xoptional_assembly_storage.hpp    |  4 ++--
 test/test_xoptional_assembly_storage.cpp       | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/xtensor/optional/xoptional_assembly_storage.hpp b/include/xtensor/optional/xoptional_assembly_storage.hpp
index 0ec1c0a44..041de952a 100644
--- a/include/xtensor/optional/xoptional_assembly_storage.hpp
+++ b/include/xtensor/optional/xoptional_assembly_storage.hpp
@@ -320,13 +320,13 @@ namespace xt
     template <class VE, class FE>
     inline auto xoptional_assembly_storage<VE, FE>::data() noexcept -> pointer
     {
-        pointer(front());
+        return pointer(front());
     }
 
     template <class VE, class FE>
     inline auto xoptional_assembly_storage<VE, FE>::data() const noexcept -> const_pointer
     {
-        const_pointer(front());
+        return const_pointer(front());
     }
 
     template <class VE, class FE>
diff --git a/test/test_xoptional_assembly_storage.cpp b/test/test_xoptional_assembly_storage.cpp
index 60a44752f..b79bc22c3 100644
--- a/test/test_xoptional_assembly_storage.cpp
+++ b/test/test_xoptional_assembly_storage.cpp
@@ -84,6 +84,24 @@ namespace xt
         ASSERT_EQ(stor[3], stor.back());
     }
 
+    TEST(xoptional_assembly_storage, data)
+    {
+        storage_type v = {56, 2, 3, 5};
+        flag_storage_type f = {false, true, true, true};
+        auto stor = optional_assembly_storage(v, f);
+
+        auto ptr = stor.data();
+        ASSERT_EQ(*ptr, stor.front());
+        ptr->value() = 12;
+        ptr->has_value() = true;
+        ASSERT_EQ(stor[0], 12);
+
+        const auto& cstor = stor;
+        auto cptr = cstor.data();
+        ASSERT_EQ(*cptr, cstor.front());
+        ASSERT_EQ(cptr->value(), 12);
+    }
+
     TEST(xoptional_assembly_storage, iterator)
     {
         storage_type v = {56, 2, 3, 5};