[MISC] Add -Wnrvo warning

include/seqan3/core/algorithm/detail/algorithm_executor_blocking.hpp

@@ -197,13 +197,14 @@ class algorithm_executor_blocking
         }
         while (status == fill_status::empty_buffer);
 
+        std::optional<algorithm_result_t> result{std::nullopt};
         if (status == fill_status::end_of_resource)
-            return {std::nullopt};
+            return result;
 
         assert(status == fill_status::non_empty_buffer);
         assert(bucket_it != buffer_it->end());
 
-        std::optional<algorithm_result_t> result = std::ranges::iter_move(bucket_it);
+        result = std::ranges::iter_move(bucket_it);
         go_to_next_result(); // Go to next buffered result.
         return result;
     }

include/seqan3/utility/detail/type_name_as_string.hpp

@@ -56,12 +56,15 @@ inline std::string const type_name_as_string = []()
     // itself, since the type is directly given by the compiler. See https://github.com/seqan/seqan3/pull/2311.
     // LCOV_EXCL_START
     if (status != 0)
-        return std::string{typeid(type).name()} + " (abi::__cxa_demangle error status (" + std::to_string(status)
-             + "): "
-             + (status == -1 ? "A memory allocation failure occurred."
-                             : (status == -2 ? "mangled_name is not a valid name under the C++ ABI mangling rules."
-                                             : (status == -3 ? "One of the arguments is invalid." : "Unknown Error")))
-             + ")";
+    {
+        demangled_name =
+            std::string{typeid(type).name()} + " (abi::__cxa_demangle error status (" + std::to_string(status) + "): "
+            + (status == -1 ? "A memory allocation failure occurred."
+                            : (status == -2 ? "mangled_name is not a valid name under the C++ ABI mangling rules."
+                                            : (status == -3 ? "One of the arguments is invalid." : "Unknown Error")))
+            + ")";
+        return demangled_name;
+    }
     // LCOV_EXCL_STOP
 
     demangled_name = std::string{std::addressof(*demangled_name_ptr)};

test/seqan3-test.cmake

@@ -61,18 +61,23 @@ if (NOT TARGET seqan3::test)
     add_library (seqan3_test INTERFACE)
     target_compile_options (seqan3_test INTERFACE "-pedantic" "-Wall" "-Wextra" "-Werror")
 
-    # GCC12 and above: Disable warning about std::hardware_destructive_interference_size not being ABI-stable.
     if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
+        # GCC12 and above: Disable warning about std::hardware_destructive_interference_size not being ABI-stable.
         if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 12)
             target_compile_options (seqan3_test INTERFACE "-Wno-interference-size")
         endif ()
-    endif ()
 
-    # GCC on arm64 (M1): Disable notes about ABI changes. Example:
-    # `parameter passing for argument of type 'std::ranges::single_view<double>' when C++17 is enabled changed to match C++14 in GCC 10.1`
-    # https://github.com/gcc-mirror/gcc/commit/56fe3ca30e1343e4f232ca539726506440e23dd3
-    if ("${CMAKE_SYSTEM_PROCESSOR}" MATCHES "arm64" AND "${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-        target_compile_options (seqan3_test INTERFACE "-Wno-psabi")
+        # Warn about failed return value optimization.
+        if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 14)
+            target_compile_options (seqan3_test INTERFACE "-Wnrvo")
+        endif ()
+
+        # GCC on arm64 (M1): Disable notes about ABI changes. Example:
+        # `parameter passing for argument of type 'std::ranges::single_view<double>' when C++17 is enabled changed to match C++14 in GCC 10.1`
+        # https://github.com/gcc-mirror/gcc/commit/56fe3ca30e1343e4f232ca539726506440e23dd3
+        if ("${CMAKE_SYSTEM_PROCESSOR}" MATCHES "arm64")
+            target_compile_options (seqan3_test INTERFACE "-Wno-psabi")
+        endif ()
     endif ()
 
     target_link_libraries (seqan3_test INTERFACE "seqan3::seqan3" "pthread")