diff --git a/.github/workflows/clang-c++11.yml b/.github/workflows/clang-c++11.yml
index 6ca727ef..39c0a0a4 100644
--- a/.github/workflows/clang-c++11.yml
+++ b/.github/workflows/clang-c++11.yml
@@ -50,7 +50,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=11 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -79,7 +78,6 @@ jobs:
         export CXX=clang++
         export CXXFLAGS="-stdlib=libc++"
         export LDFLAGS="-stdlib=libc++"
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=11 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -101,7 +99,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=11 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
diff --git a/.github/workflows/clang-c++14.yml b/.github/workflows/clang-c++14.yml
index 3ddb0cfa..e7909302 100644
--- a/.github/workflows/clang-c++14.yml
+++ b/.github/workflows/clang-c++14.yml
@@ -50,7 +50,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=14 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -79,7 +78,6 @@ jobs:
         export CXX=clang++
         export CXXFLAGS="-stdlib=libc++"
         export LDFLAGS="-stdlib=libc++"
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=14 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -101,7 +99,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=14 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
diff --git a/.github/workflows/clang-c++17.yml b/.github/workflows/clang-c++17.yml
index ccec532b..54b05957 100644
--- a/.github/workflows/clang-c++17.yml
+++ b/.github/workflows/clang-c++17.yml
@@ -50,7 +50,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=17 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -79,7 +78,6 @@ jobs:
         export CXX=clang++
         export CXXFLAGS="-stdlib=libc++"
         export LDFLAGS="-stdlib=libc++"
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=17 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -101,7 +99,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=17 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
diff --git a/.github/workflows/clang-c++20.yml b/.github/workflows/clang-c++20.yml
index 0d3fa3f7..eb6d6bf5 100644
--- a/.github/workflows/clang-c++20.yml
+++ b/.github/workflows/clang-c++20.yml
@@ -62,7 +62,6 @@ jobs:
         export CXX=clang++-17
         export CXXFLAGS="-stdlib=libc++"
         export LDFLAGS="-stdlib=libc++"
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=20 ./
         clang-17 --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -91,7 +90,6 @@ jobs:
       run: |
         export CC=clang-17
         export CXX=clang++-17
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=20 ./
         clang-17 --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -120,7 +118,6 @@ jobs:
       run: |
         export CC=clang-17
         export CXX=clang++-17
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=20 ./
         clang-17 --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -149,7 +146,6 @@ jobs:
       run: |
         export CC=clang-17
         export CXX=clang++-17
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=20 ./
         clang-17 --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -171,7 +167,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=20 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -193,7 +188,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=20 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -215,7 +209,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=20 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -237,7 +230,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=20 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
diff --git a/.github/workflows/clang-c++23.yml b/.github/workflows/clang-c++23.yml
index d25a346c..97ba5af3 100644
--- a/.github/workflows/clang-c++23.yml
+++ b/.github/workflows/clang-c++23.yml
@@ -57,12 +57,19 @@ jobs:
         export CXX=clang++
         export CXXFLAGS="-stdlib=libc++"
         export LDFLAGS="-stdlib=libc++"
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
-        cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
+        cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 -DETL_ENABLE_SANITIZER=ON ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
 
     - name: Run tests
+      # The system libc++/libc++abi are not built with ASan. Exception objects
+      # (e.g. std::runtime_error's reference counted string) are allocated with
+      # operator new inside libc++.so, but released with free() inside
+      # libc++abi.so, which AddressSanitizer reports as an alloc-dealloc-mismatch.
+      # This is a libc++ packaging issue, not an ETL defect, so the check is
+      # disabled for this job only.
+      env:
+        ASAN_OPTIONS: alloc_dealloc_mismatch=0
       run: ./test/etl_tests -v
 
   build-clang-cpp23-linux-no-stl:
@@ -79,8 +86,7 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
-        cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
+        cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 -DETL_ENABLE_SANITIZER=ON ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
     
@@ -101,8 +107,7 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
-        cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
+        cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 -DETL_ENABLE_SANITIZER=ON ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
 
@@ -123,8 +128,7 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
-        cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
+        cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 -DETL_ENABLE_SANITIZER=ON ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
 
@@ -145,8 +149,7 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
-        cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
+        cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 -DETL_ENABLE_SANITIZER=ON ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
 
@@ -167,8 +170,7 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
-        cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
+        cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 -DETL_ENABLE_SANITIZER=ON ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
 
@@ -189,8 +191,7 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
-        cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
+        cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 -DETL_ENABLE_SANITIZER=ON ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
 
@@ -211,8 +212,7 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
-        cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
+        cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 -DETL_ENABLE_SANITIZER=ON ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
 
diff --git a/.github/workflows/clang-c++26.yml b/.github/workflows/clang-c++26.yml
index e118c66a..5905289a 100644
--- a/.github/workflows/clang-c++26.yml
+++ b/.github/workflows/clang-c++26.yml
@@ -55,7 +55,6 @@ jobs:
           export CXX=clang++ && \
           export CXXFLAGS=-stdlib=libc++ && \
           export LDFLAGS=-stdlib=libc++ && \
-          export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0 && \
           cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=26 ./ && \
           clang --version && \
           make -j \$(getconf _NPROCESSORS_ONLN) && \
@@ -77,7 +76,6 @@ jobs:
           cd /workspaces/etl && \
           export CC=clang && \
           export CXX=clang++ && \
-          export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0 && \
           cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=26 ./ && \
           clang --version && \
           make -j \$(getconf _NPROCESSORS_ONLN) && \
@@ -99,7 +97,6 @@ jobs:
           cd /workspaces/etl && \
           export CC=clang && \
           export CXX=clang++ && \
-          export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0 && \
           cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=26 ./ && \
           clang --version && \
           make -j \$(getconf _NPROCESSORS_ONLN) && \
@@ -121,7 +118,6 @@ jobs:
           cd /workspaces/etl && \
           export CC=clang && \
           export CXX=clang++ && \
-          export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0 && \
           cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=26 ./ && \
           clang --version && \
           make -j \$(getconf _NPROCESSORS_ONLN) && \
@@ -143,7 +139,6 @@ jobs:
           cd /workspaces/etl && \
           export CC=clang && \
           export CXX=clang++ && \
-          export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0 && \
           cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=26 ./ && \
           clang --version && \
           make -j \$(getconf _NPROCESSORS_ONLN) && \
@@ -163,7 +158,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=26 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -185,7 +179,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=26 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -207,7 +200,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=26 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
@@ -229,7 +221,6 @@ jobs:
       run: |
         export CC=clang
         export CXX=clang++
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         cmake -D BUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=26 ./
         clang --version
         make -j "$(getconf _NPROCESSORS_ONLN)"
diff --git a/.github/workflows/gcc-c++11.yml b/.github/workflows/gcc-c++11.yml
index 4d33a909..71a5809e 100644
--- a/.github/workflows/gcc-c++11.yml
+++ b/.github/workflows/gcc-c++11.yml
@@ -49,7 +49,6 @@ jobs:
     - name: Build
       run: |
         git fetch
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=11 ./
@@ -72,7 +71,6 @@ jobs:
     - name: Build
       run: |
         git fetch
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=11 ./
diff --git a/.github/workflows/gcc-c++14.yml b/.github/workflows/gcc-c++14.yml
index bc7cca67..0cb6dc2c 100644
--- a/.github/workflows/gcc-c++14.yml
+++ b/.github/workflows/gcc-c++14.yml
@@ -48,7 +48,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=14 ./
@@ -70,7 +69,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=14 ./
diff --git a/.github/workflows/gcc-c++17.yml b/.github/workflows/gcc-c++17.yml
index 1378fc69..4968a87d 100644
--- a/.github/workflows/gcc-c++17.yml
+++ b/.github/workflows/gcc-c++17.yml
@@ -48,7 +48,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=17 ./
@@ -70,7 +69,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=17 ./
diff --git a/.github/workflows/gcc-c++20.yml b/.github/workflows/gcc-c++20.yml
index 6e004456..68be97d8 100644
--- a/.github/workflows/gcc-c++20.yml
+++ b/.github/workflows/gcc-c++20.yml
@@ -48,7 +48,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=20 ./
@@ -70,7 +69,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=20 ./
@@ -92,7 +90,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=20 ./
@@ -114,7 +111,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc
         export CXX=g++
         cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=20 ./
diff --git a/.github/workflows/gcc-c++23.yml b/.github/workflows/gcc-c++23.yml
index a7e29e56..65cf7dc4 100644
--- a/.github/workflows/gcc-c++23.yml
+++ b/.github/workflows/gcc-c++23.yml
@@ -48,7 +48,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc-14
         export CXX=g++-14
         cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
@@ -70,7 +69,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc-14
         export CXX=g++-14
         cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
@@ -92,7 +90,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc-14
         export CXX=g++-14
         cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
@@ -114,7 +111,6 @@ jobs:
 
     - name: Build
       run: |
-        export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0
         export CC=gcc-14
         export CXX=g++-14
         cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=23 -DETL_OPTIMISATION=-O3 ./
diff --git a/.github/workflows/gcc-c++26.yml b/.github/workflows/gcc-c++26.yml
index 63677261..38506641 100644
--- a/.github/workflows/gcc-c++26.yml
+++ b/.github/workflows/gcc-c++26.yml
@@ -50,7 +50,6 @@ jobs:
       run: |
         docker run --rm --user root -v ${{ github.workspace }}:/workspaces/etl etl-ubuntu-2604 bash -c "\
           cd /workspaces/etl && \
-          export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0 && \
           export CC=gcc && \
           export CXX=g++ && \
           cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=26 ./ && \
@@ -72,7 +71,6 @@ jobs:
       run: |
         docker run --rm --user root -v ${{ github.workspace }}:/workspaces/etl etl-ubuntu-2604 bash -c "\
           cd /workspaces/etl && \
-          export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0 && \
           export CC=gcc && \
           export CXX=g++ && \
           cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=OFF -DETL_CXX_STANDARD=26 ./ && \
@@ -94,7 +92,6 @@ jobs:
       run: |
         docker run --rm --user root -v ${{ github.workspace }}:/workspaces/etl etl-ubuntu-2604 bash -c "\
           cd /workspaces/etl && \
-          export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0 && \
           export CC=gcc && \
           export CXX=g++ && \
           cmake -DBUILD_TESTS=ON -DNO_STL=OFF -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=26 ./ && \
@@ -116,7 +113,6 @@ jobs:
       run: |
         docker run --rm --user root -v ${{ github.workspace }}:/workspaces/etl etl-ubuntu-2604 bash -c "\
           cd /workspaces/etl && \
-          export ASAN_OPTIONS=alloc_dealloc_mismatch=0,detect_leaks=0 && \
           export CC=gcc && \
           export CXX=g++ && \
           cmake -DBUILD_TESTS=ON -DNO_STL=ON -DETL_USE_TYPE_TRAITS_BUILTINS=OFF -DETL_USER_DEFINED_TYPE_TRAITS=OFF -DETL_FORCE_TEST_CPP03_IMPLEMENTATION=ON -DETL_CXX_STANDARD=26 ./ && \
diff --git a/include/etl/expected.h b/include/etl/expected.h
index 1feb1487..49b99aad 100644
--- a/include/etl/expected.h
+++ b/include/etl/expected.h
@@ -1435,6 +1435,11 @@ namespace etl
     return lhs.error() == rhs.error();
   }
 
+#include "private/diagnostic_uninitialized_push.h"
+  //*******************************************
+  // The error is only read when the expected does not have a value, in which
+  // case it is always fully constructed. GCC can emit a false positive
+  // -Wmaybe-uninitialized when these are inlined at high optimisation levels.
   //*******************************************
   template <typename TError, typename TError2>
   ETL_CONSTEXPR14 bool operator==(const etl::expected<void, TError>& lhs, const etl::expected<void, TError2>& rhs)
@@ -1460,6 +1465,7 @@ namespace etl
     }
     return lhs.error() == rhs.error();
   }
+#include "private/diagnostic_pop.h"
 
   //*******************************************
   template <typename TError, typename TError2>
diff --git a/include/etl/inplace_function.h b/include/etl/inplace_function.h
index 63760d15..e9211702 100644
--- a/include/etl/inplace_function.h
+++ b/include/etl/inplace_function.h
@@ -1126,8 +1126,13 @@ namespace etl
     {
     }
 
+  #include "private/diagnostic_uninitialized_push.h"
     //*************************************************************************
     // clone_from
+    //
+    // GCC can emit a false positive -Wmaybe-uninitialized for the source
+    // storage when this is inlined into a copy constructor at high
+    // optimisation levels. The source object is always fully constructed.
     //*************************************************************************
     template <size_t Other_Object_Size, size_t Other_Object_Alignment>
     void clone_from(const etl::inplace_function<TReturn(TArgs...), Other_Object_Size, Other_Object_Alignment>& other)
@@ -1139,6 +1144,7 @@ namespace etl
         vtable->copy(&other.storage, &storage);
       }
     }
+  #include "private/diagnostic_pop.h"
 
     //*************************************************************************
     // move_from
diff --git a/include/etl/invoke.h b/include/etl/invoke.h
index 52ad388c..d2644748 100644
--- a/include/etl/invoke.h
+++ b/include/etl/invoke.h
@@ -39,6 +39,8 @@ SOFTWARE.
 
 #if ETL_USING_CPP11
 
+  #include "private/diagnostic_array_bounds_push.h"
+
 namespace etl
 {
   //****************************************************************************
@@ -387,5 +389,7 @@ namespace etl
   #endif
 } // namespace etl
 
+  #include "private/diagnostic_pop.h"
+
 #endif // ETL_USING_CPP11
 #endif // ETL_INVOKE_INCLUDED
diff --git a/include/etl/message_packet.h b/include/etl/message_packet.h
index fdaed2b3..de56fb9c 100644
--- a/include/etl/message_packet.h
+++ b/include/etl/message_packet.h
@@ -305,6 +305,7 @@ namespace etl
       (add_new_message_type<TMessageTypes>(etl::move(msg)) || ...);
     }
 
+  #include "private/diagnostic_array_bounds_push.h"
   #include "private/diagnostic_uninitialized_push.h"
     //********************************************
     /// Only enabled for types that are in the typelist.
@@ -318,6 +319,9 @@ namespace etl
     }
   #include "private/diagnostic_pop.h"
 
+  #include "private/diagnostic_pop.h"
+
+  #include "private/diagnostic_array_bounds_push.h"
   #include "private/diagnostic_uninitialized_push.h"
     //********************************************
     template <typename TType>
@@ -336,6 +340,9 @@ namespace etl
     }
   #include "private/diagnostic_pop.h"
 
+  #include "private/diagnostic_pop.h"
+
+  #include "private/diagnostic_array_bounds_push.h"
   #include "private/diagnostic_uninitialized_push.h"
     //********************************************
     template <typename TType>
@@ -352,6 +359,8 @@ namespace etl
         return false;
       }
     }
+  #include "private/diagnostic_pop.h"
+
   #include "private/diagnostic_pop.h"
 
     typename etl::aligned_storage<SIZE, ALIGNMENT>::type data;
diff --git a/include/etl/not_null.h b/include/etl/not_null.h
index dc1ada2f..de0ebe22 100644
--- a/include/etl/not_null.h
+++ b/include/etl/not_null.h
@@ -35,6 +35,7 @@ SOFTWARE.
 #include "error_handler.h"
 #include "exception.h"
 #include "memory.h"
+#include "nullptr.h"
 #include "type_traits.h"
 
 namespace etl
@@ -95,7 +96,16 @@ namespace etl
     ETL_CONSTEXPR14 explicit not_null(underlying_type ptr_)
       : ptr(ptr_)
     {
-      ETL_ASSERT(ptr_ != ETL_NULLPTR, ETL_ERROR(not_null_contains_null));
+      if (etl::is_constant_evaluated())
+      {
+        // ETL_IS_FOLDED_NULL keeps the compile time rejection of null working
+        // when the undefined behaviour sanitizer instruments the comparison.
+        ETL_ASSERT(!ETL_IS_FOLDED_NULL(ptr_), ETL_ERROR(not_null_contains_null));
+      }
+      else
+      {
+        ETL_ASSERT(ptr_ != ETL_NULLPTR, ETL_ERROR(not_null_contains_null));
+      }
     }
 
     //*********************************
@@ -112,7 +122,14 @@ namespace etl
     //*********************************
     ETL_CONSTEXPR14 not_null& operator=(underlying_type rhs)
     {
-      ETL_ASSERT_OR_RETURN_VALUE(rhs != ETL_NULLPTR, ETL_ERROR(not_null_contains_null), *this);
+      if (etl::is_constant_evaluated())
+      {
+        ETL_ASSERT_OR_RETURN_VALUE(!ETL_IS_FOLDED_NULL(rhs), ETL_ERROR(not_null_contains_null), *this);
+      }
+      else
+      {
+        ETL_ASSERT_OR_RETURN_VALUE(rhs != ETL_NULLPTR, ETL_ERROR(not_null_contains_null), *this);
+      }
 
       ptr = rhs;
 
diff --git a/include/etl/nullptr.h b/include/etl/nullptr.h
index 581305ae..57f1c8bd 100644
--- a/include/etl/nullptr.h
+++ b/include/etl/nullptr.h
@@ -78,4 +78,26 @@ namespace etl
 #endif
 } // namespace etl
 
+//*****************************************************************************
+/// True when the compiler can fold the comparison at compile time and it yields
+/// null.
+///
+/// Normally the comparison folds for any pointer that is a constant expression,
+/// so this is equivalent to a plain null check. Under GCC's undefined behaviour
+/// sanitizer, however, the comparison is instrumented and only folds for a null
+/// pointer constant, not for the address of an object or function.
+/// __builtin_constant_p filters out the latter, which would otherwise make the
+/// enclosing expression non-constant and reject perfectly valid code.
+///
+/// Only meaningful during constant evaluation. At run time
+/// __builtin_constant_p is false for any pointer that is not a compile time
+/// constant, so this reports false for a genuine null pointer. Callers must
+/// use a plain comparison against ETL_NULLPTR on the run time path.
+//*****************************************************************************
+#if ETL_USING_BUILTIN_CONSTANT_P
+  #define ETL_IS_FOLDED_NULL(p) (__builtin_constant_p((p) == ETL_NULLPTR) && ((p) == ETL_NULLPTR))
+#else
+  #define ETL_IS_FOLDED_NULL(p) ((p) == ETL_NULLPTR)
+#endif
+
 #endif
diff --git a/include/etl/optional.h b/include/etl/optional.h
index d0c10b44..f675354e 100644
--- a/include/etl/optional.h
+++ b/include/etl/optional.h
@@ -703,6 +703,11 @@ namespace etl
         }
 #endif
 
+#include "private/diagnostic_uninitialized_push.h"
+        //*******************************
+        // GCC may warn that 'valid' is used uninitialised when the storage of a
+        // nested optional is inspected through an inlined destructor chain.
+        // The flag is always initialised by the constructors, so this is a false positive.
         //*******************************
         ETL_CONSTEXPR20_STL
         void destroy()
@@ -713,6 +718,7 @@ namespace etl
             valid = false;
           }
         }
+#include "private/diagnostic_pop.h"
 
         //*******************************
         union union_type
diff --git a/include/etl/private/delegate_cpp11.h b/include/etl/private/delegate_cpp11.h
index eafbde77..c351da9c 100644
--- a/include/etl/private/delegate_cpp11.h
+++ b/include/etl/private/delegate_cpp11.h
@@ -492,7 +492,7 @@ namespace etl
     //*************************************************************************
     /// Assignment
     //*************************************************************************
-    delegate& operator=(const delegate& rhs) = default;
+    ETL_CONSTEXPR14 delegate& operator=(const delegate& rhs) = default;
 
     //*************************************************************************
     /// Create from Lambda or Functor.
diff --git a/include/etl/private/variant_variadic.h b/include/etl/private/variant_variadic.h
index 5f6444b2..aaedb064 100644
--- a/include/etl/private/variant_variadic.h
+++ b/include/etl/private/variant_variadic.h
@@ -94,6 +94,15 @@ namespace etl
     template <size_t Index, typename THead, typename... TRest>
     struct variant_operations<Index, THead, TRest...>
     {
+  #include "diagnostic_uninitialized_push.h"
+      //*************************************************************************
+      // destroy
+      //
+      // GCC can emit a false positive -Wmaybe-uninitialized when this is inlined
+      // into a variant destructor at high optimisation levels, as it cannot
+      // prove that the branch for an inactive alternative is never taken.
+      // The alternative identified by type_id is always fully constructed.
+      //*************************************************************************
       static void destroy(char* data, size_t type_id)
       {
         if (type_id == Index)
@@ -105,6 +114,7 @@ namespace etl
           variant_operations<Index + 1, TRest...>::destroy(data, type_id);
         }
       }
+  #include "diagnostic_pop.h"
 
       static void copy(char* dst, const char* src, size_t type_id)
       {
@@ -156,6 +166,14 @@ namespace etl
 
     private:
 
+  #include "diagnostic_uninitialized_push.h"
+      //*************************************************************************
+      // The *_impl functions below read the alternative identified by type_id,
+      // which is always fully constructed. GCC can emit a false positive
+      // -Wmaybe-uninitialized when these are inlined at high optimisation
+      // levels, as it cannot prove that the branch for an inactive alternative
+      // is never taken.
+      //*************************************************************************
       static void copy_impl(char* dst, const char* src, etl::true_type)
       {
         ::new (dst) THead(*reinterpret_cast<const THead*>(src));
@@ -183,6 +201,7 @@ namespace etl
       }
 
       static void move_assign_impl(char*, const char*, etl::false_type) {}
+  #include "diagnostic_pop.h"
     };
 
     //*******************************************
diff --git a/include/etl/profiles/determine_builtin_support.h b/include/etl/profiles/determine_builtin_support.h
index 3db1a474..6340e6e3 100644
--- a/include/etl/profiles/determine_builtin_support.h
+++ b/include/etl/profiles/determine_builtin_support.h
@@ -232,6 +232,10 @@ SOFTWARE.
     #define ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED __has_builtin(__builtin_is_constant_evaluated)
   #endif
 
+  #if !defined(ETL_USING_BUILTIN_CONSTANT_P)
+    #define ETL_USING_BUILTIN_CONSTANT_P __has_builtin(__builtin_constant_p)
+  #endif
+
   #if !defined(ETL_USING_BUILTIN_BIT_CAST)
     #define ETL_USING_BUILTIN_BIT_CAST __has_builtin(__builtin_bit_cast)
   #endif
@@ -444,6 +448,16 @@ SOFTWARE.
   #define ETL_USING_BUILTIN_BUILTIN_IS_CPP_TRIVIALLY_RELOCATABLE 0
 #endif
 
+// __builtin_constant_p predates __has_builtin on GCC and Clang, so enable it for
+// those compilers when __has_builtin was not available to detect it.
+#if !defined(ETL_USING_BUILTIN_CONSTANT_P) && (defined(__GNUC__) || defined(__clang__))
+  #define ETL_USING_BUILTIN_CONSTANT_P 1
+#endif
+
+#if !defined(ETL_USING_BUILTIN_CONSTANT_P)
+  #define ETL_USING_BUILTIN_CONSTANT_P 0
+#endif
+
 #if !defined(ETL_USING_BUILTIN_BIT_CAST)
   #define ETL_USING_BUILTIN_BIT_CAST 0
 #endif
@@ -470,6 +484,7 @@ namespace etl
     static ETL_CONSTANT bool using_builtin_is_trivially_copyable                = (ETL_USING_BUILTIN_IS_TRIVIALLY_COPYABLE == 1);
     static ETL_CONSTANT bool using_builtin_underlying_type                      = (ETL_USING_BUILTIN_UNDERLYING_TYPE == 1);
     static ETL_CONSTANT bool using_builtin_is_constant_evaluated                = (ETL_USING_BUILTIN_IS_CONSTANT_EVALUATED == 1);
+    static ETL_CONSTANT bool using_builtin_constant_p                           = (ETL_USING_BUILTIN_CONSTANT_P == 1);
     static ETL_CONSTANT bool using_builtin_memcpy                               = (ETL_USING_BUILTIN_MEMCPY == 1);
     static ETL_CONSTANT bool using_builtin_memmove                              = (ETL_USING_BUILTIN_MEMMOVE == 1);
     static ETL_CONSTANT bool using_builtin_memset                               = (ETL_USING_BUILTIN_MEMSET == 1);
diff --git a/include/etl/to_arithmetic.h b/include/etl/to_arithmetic.h
index 941fc09b..bba59f88 100644
--- a/include/etl/to_arithmetic.h
+++ b/include/etl/to_arithmetic.h
@@ -713,7 +713,9 @@ namespace etl
             const uvalue_t                                    uvalue = static_cast<uvalue_t>(accumulator_result.value());
 
             // Convert from the accumulator type to the desired type.
-            result = (is_negative ? static_cast<TValue>(static_cast<TValue>(0) - static_cast<TValue>(uvalue)) : etl::bit_cast<TValue>(uvalue));
+            // The negation is performed on the unsigned type to avoid signed overflow
+            // when the value is the most negative value for the type.
+            result = (is_negative ? etl::bit_cast<TValue>(static_cast<uvalue_t>(static_cast<uvalue_t>(0) - uvalue)) : etl::bit_cast<TValue>(uvalue));
           }
         }
       }
diff --git a/include/etl/type_traits.h b/include/etl/type_traits.h
index 0c9da447..87b7607b 100644
--- a/include/etl/type_traits.h
+++ b/include/etl/type_traits.h
@@ -3603,8 +3603,9 @@ namespace etl
   template <typename T>
   struct is_nothrow_relocatable
   {
-    // In builtins mode, conservatively use trivially_relocatable as the definition
-    static ETL_CONSTANT bool value = etl::is_trivially_relocatable<T>::value;
+    static ETL_CONSTANT bool value = etl::is_trivially_relocatable<T>::value
+                             || (etl::is_nothrow_move_constructible<typename etl::remove_all_extents<T>::type>::value
+                                 && etl::is_nothrow_destructible<typename etl::remove_all_extents<T>::type>::value);
   };
 
 #elif defined(ETL_USER_DEFINED_TYPE_TRAITS) && !defined(ETL_USE_TYPE_TRAITS_BUILTINS)
diff --git a/test/test_delegate.cpp b/test/test_delegate.cpp
index c4e870bd..60a8965e 100644
--- a/test/test_delegate.cpp
+++ b/test/test_delegate.cpp
@@ -2183,6 +2183,65 @@ namespace
     }
   #endif
 
+  #if ETL_USING_CPP17
+    //*************************************************************************
+    // Verify that copy assigning a delegate, and comparing against a default
+    // constructed one, are usable in a constant expression.
+    //*************************************************************************
+    TEST(test_constexpr_copy_assignment_and_clear)
+    {
+      using delegate_type = etl::delegate<void(void)>;
+
+      // Copy assignment from a bound delegate.
+      constexpr auto copy_assigned = []() constexpr
+      {
+        const delegate_type source(&free_void);
+        delegate_type       d;
+        d = source;
+        return d;
+      };
+
+      constexpr delegate_type d1 = copy_assigned();
+
+      static_assert(d1.is_valid(), "a copy assigned delegate should be valid");
+      static_assert(d1 == delegate_type(&free_void), "a copy assigned delegate should compare equal to its source");
+
+      // Copy assignment from a default constructed delegate, and comparing an
+      // unbound delegate against another one. Neither may inspect the null stub
+      // pointer, which the undefined behaviour sanitizer makes non-constant.
+      constexpr auto cleared = []() constexpr
+      {
+        delegate_type d(&free_void);
+        d = delegate_type();
+        return d;
+      };
+
+      constexpr delegate_type d2 = cleared();
+
+      static_assert(!d2.is_valid(), "a delegate assigned from a default constructed one should be invalid");
+      static_assert(d2 == delegate_type(), "an unbound delegate should compare equal to a default constructed one");
+      static_assert(d2 != d1, "an unbound delegate should not compare equal to a bound one");
+
+      // The same operations must still behave identically at run time.
+      delegate_type d3;
+      d3 = d1;
+      CHECK_TRUE(d3.is_valid());
+      CHECK(d3 == d1);
+
+      d3 = delegate_type();
+      CHECK_FALSE(d3.is_valid());
+      CHECK(d3 == delegate_type());
+
+      // Assigning a null function pointer clears the delegate at run time.
+      // This is deliberately not checked in a constant expression: the null
+      // test cannot be folded there when the sanitizer instruments it.
+      delegate_type d4(&free_void);
+      d4 = static_cast<void (*)()>(ETL_NULLPTR);
+      CHECK_FALSE(d4.is_valid());
+      CHECK(d4 == delegate_type());
+    }
+  #endif
+
     TEST(test_delegate_clear_equals_default_constructed)
     {
       using delegate_type = etl::delegate<void(int, int)>;
diff --git a/test/test_optional.cpp b/test/test_optional.cpp
index a6ffc5a7..905de3cb 100644
--- a/test/test_optional.cpp
+++ b/test/test_optional.cpp
@@ -35,6 +35,12 @@ SOFTWARE.
 #include <type_traits>
 #include <utility>
 
+// GCC can emit false positive -Wmaybe-uninitialized warnings inside the test data
+// types when optional's storage is inspected through inlined, never-taken branches.
+// The diagnostic is raised late (after inlining), so the suppression has to cover the
+// whole translation unit. It is popped at the end of the file.
+#include "etl/private/diagnostic_uninitialized_push.h"
+
 #include "data.h"
 #include "etl/algorithm.h"
 #include "etl/optional.h"
@@ -1949,3 +1955,5 @@ namespace
 #endif
   }
 } // namespace
+
+#include "etl/private/diagnostic_pop.h"