From ea91dabee5aa0186cedf62c2cfae62b9f9d29008 Mon Sep 17 00:00:00 2001
From: Roland Reichwein <Roland.Reichwein@bmw.de>
Date: Wed, 10 Sep 2025 11:37:30 +0200
Subject: [PATCH] Regression fix: Support zero arguments emplace() in
 etl::optional (#1183)

* Added coderabbitai configuration

* Added builtin mem function tests

* Modified etl::typed_storage

* Modified etl::typed_storage

# Conflicts:
#	include/etl/alignment.h

* Added ETL_NOEXCEPT and ETL_NOEXCEPT_IF_NO_THROW

* Added etl::typed_storage_ext and swap for same

* Added etl::typed_storage_ext and swap for same

# Conflicts:
#	include/etl/alignment.h

* Added release notes

* Fixes to GCC -O2 errors

* Changed char* parameters to value_type* parameters

* Fixed compilation issues for const containers unit tests

* Added automatic selection of __builtin_memxxx functions for GCC and clang

* Added enhanced coderabbit configuration

* Updated version and release notes

* Disabled constexpr const container tests for C++11

* Attempted fixes for MacOS compilation

* Attempted fixes for MacOS compilation

* Attempted fixes for MacOS compilation

* Attempted fixes for MacOS compilation

* Updated version and release notes

* feat: removed unreachable break statements (#1169)

* Updated version and release notes

* Modified etl::typed_storage

# Conflicts:
#	include/etl/alignment.h

* Support zero arguments emplace() in etl::optional

For non-fundamental types, a recent change in etl::optional was
introduced that doesn't support zero arguments emplace() anymore.

This change fixes it and adds the respective test.

---------

Co-authored-by: John Wellbelove <john.wellbelove@asterconsulting.co.uk>
Co-authored-by: Drew Rife <darife@jlg.com>
---
 include/etl/optional.h | 11 +++++++++++
 test/test_optional.cpp | 16 ++++++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/include/etl/optional.h b/include/etl/optional.h
index 48289116..e8e40439 100644
--- a/include/etl/optional.h
+++ b/include/etl/optional.h
@@ -536,6 +536,17 @@ namespace etl
 
         return storage.u.value;
       }
+
+      //*************************************************************************
+      /// Emplaces with zero arguments, i.e. default construct emplace.
+      //*************************************************************************
+      ETL_CONSTEXPR20_STL
+      T& emplace()
+      {
+        storage.construct();
+
+        return storage.u.value;
+      }
 #else
       //*************************************************************************
       /// Emplaces a value.
diff --git a/test/test_optional.cpp b/test/test_optional.cpp
index e9623b87..c5a34d08 100644
--- a/test/test_optional.cpp
+++ b/test/test_optional.cpp
@@ -218,15 +218,27 @@ namespace
     }
 
     //*************************************************************************
-    TEST(test_emplace_zero_parameters)
+    TEST(test_emplace_zero_parameters_fundamental)
     {
       etl::optional<std::uint8_t> result = 1;
-      result.emplace();
+      CHECK_EQUAL(0, static_cast<int>(result.emplace()));
 
       CHECK_TRUE(result.has_value());
       CHECK_EQUAL(0, int(result.value()));
     }
 
+    //*************************************************************************
+    TEST(test_emplace_zero_parameters_non_fundamental)
+    {
+      etl::optional<std::string> result = std::string("abc");
+
+      std::string& ref = result.emplace();
+      CHECK_EQUAL(std::string(), ref);
+      CHECK_EQUAL(&ref, &result.value());
+      CHECK_TRUE(result.has_value());
+      CHECK_EQUAL("", std::string(result.value()));
+    }
+
     //*************************************************************************
     TEST(test_emplace_return)
     {