Add EXECUTORCH_USE_SANITIZER CMake option for ASAN+UBSAN support (#17114)

Add a first-class CMake option to enable AddressSanitizer and
UndefinedBehaviorSanitizer for catching memory bugs and undefined
behavior in C++ tests.

Previously, sanitizers were enabled via a CXXFLAGS hack in utils.sh
that only applied to the initial build, but the test build in
run_oss_cpp_tests.sh would rebuild from scratch without sanitizers.
This meant C++ tests (including runtime, portable kernels, and XNNPACK
tests) were not actually running with sanitizer coverage.

All unittest in pull mode ("unittest / linux" and "unittest /macos")
will be compiling and running with sanitizer on from now on.

The new design:
- Adds EXECUTORCH_USE_SANITIZER as a proper CMake option
- CI scripts export EXECUTORCH_USE_SANITIZER=ON for Debug builds
- Both utils.sh and run_oss_cpp_tests.sh check the env var and pass
  the CMake flag, ensuring consistent sanitizer coverage
- CMakeLists.txt applies -fsanitize=address,undefined flags globally

- Verified CMake configuration shows "Sanitizers enabled: address,
undefined"
- Verified compile_commands.json contains -fsanitize=address,undefined
- Built and ran runtime_core_test with sanitizers, confirmed ASAN/UBSAN
  symbols present in binary (nm shows ___asan_* and ___ubsan_* symbols)
- Verified Debug mode enables sanitizers, Release mode does not
- All shell scripts pass syntax check (bash -n)

Author: mergennachin

.ci/scripts/unittest-linux.sh

@@ -20,6 +20,11 @@ if [[ "$BUILD_TOOL" == "cmake" ]]; then
     # Setup swiftshader and Vulkan SDK which are required to build the Vulkan delegate
     source .ci/scripts/setup-vulkan-linux-deps.sh
 
+    # Enable sanitizers for Debug builds
+    if [[ "$BUILD_MODE" == "Debug" ]]; then
+        export EXECUTORCH_USE_SANITIZER=ON
+    fi
+
     # We need the runner to test the built library.
     PYTHON_EXECUTABLE=python \
     CMAKE_ARGS="-DEXECUTORCH_BUILD_EXTENSION_EVALUE_UTIL=ON -DEXECUTORCH_BUILD_EXTENSION_RUNNER_UTIL=ON -DEXECUTORCH_BUILD_EXECUTOR_RUNNER=ON -DEXECUTORCH_BUILD_TESTS=ON" \

.ci/scripts/unittest-macos.sh

@@ -19,6 +19,11 @@ export TMP_DIR=$(mktemp -d)
 export PATH="${TMP_DIR}:$PATH"
 trap 'rm -rfv ${TMP_DIR}' EXIT
 
+# Enable sanitizers for Debug builds
+if [[ "$BUILD_MODE" == "Debug" ]]; then
+    export EXECUTORCH_USE_SANITIZER=ON
+fi
+
 # Setup MacOS dependencies as there is no Docker support on MacOS atm
 # We need the runner to test the built library.
 PYTHON_EXECUTABLE=python \

.ci/scripts/utils.sh

@@ -164,14 +164,18 @@ build_executorch_runner_cmake() {
   clean_executorch_install_folders
   mkdir "${CMAKE_OUTPUT_DIR}"
 
-  if [[ $1 == "Debug" ]]; then
-      CXXFLAGS="-fsanitize=address,undefined"
-  else
-      CXXFLAGS=""
+  local build_type="${1:-Release}"
+  local sanitizer_flag=""
+
+  if [[ "${EXECUTORCH_USE_SANITIZER:-OFF}" == "ON" ]]; then
+      sanitizer_flag="-DEXECUTORCH_USE_SANITIZER=ON"
   fi
-  CXXFLAGS="$CXXFLAGS" retry cmake \
+
+  retry cmake \
     -DPYTHON_EXECUTABLE="${PYTHON_EXECUTABLE}" \
-    -DCMAKE_BUILD_TYPE="${1:-Release}" \
+    -DCMAKE_BUILD_TYPE="${build_type}" \
+    ${sanitizer_flag} \
+    ${CMAKE_ARGS:-} \
     -B${CMAKE_OUTPUT_DIR} .
 
   if [ "$(uname)" == "Darwin" ]; then

CMakeLists.txt

@@ -74,6 +74,34 @@ if(NOT CMAKE_BUILD_TYPE)
 endif()
 announce_configured_options(CMAKE_BUILD_TYPE)
 
+# Sanitizer support (ASAN + UBSAN)
+if(EXECUTORCH_USE_SANITIZER)
+  if(MSVC)
+    message(WARNING "Sanitizers are not fully supported on MSVC, skipping")
+  else()
+    set(EXECUTORCH_SANITIZER_FLAGS
+        "-fsanitize=address,undefined -fno-omit-frame-pointer"
+    )
+    # Suppress deprecation warnings on macOS (third-party code like flatcc uses
+    # deprecated sprintf)
+    if(APPLE)
+      set(EXECUTORCH_SANITIZER_FLAGS
+          "${EXECUTORCH_SANITIZER_FLAGS} -Wno-deprecated-declarations"
+      )
+    endif()
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${EXECUTORCH_SANITIZER_FLAGS}")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${EXECUTORCH_SANITIZER_FLAGS}")
+    set(CMAKE_EXE_LINKER_FLAGS
+        "${CMAKE_EXE_LINKER_FLAGS} ${EXECUTORCH_SANITIZER_FLAGS}"
+    )
+    set(CMAKE_SHARED_LINKER_FLAGS
+        "${CMAKE_SHARED_LINKER_FLAGS} ${EXECUTORCH_SANITIZER_FLAGS}"
+    )
+    message(STATUS "Sanitizers enabled: address, undefined")
+  endif()
+endif()
+announce_configured_options(EXECUTORCH_USE_SANITIZER)
+
 if(NOT PYTHON_EXECUTABLE)
   resolve_python_executable()
 endif()

test/run_oss_cpp_tests.sh

@@ -32,9 +32,16 @@ build_executorch() {
   if [ -x "$(command -v glslc)" ]; then
     BUILD_VULKAN="ON"
   fi
+
+  SANITIZER_FLAG=""
+  if [[ "${EXECUTORCH_USE_SANITIZER:-OFF}" == "ON" ]]; then
+    SANITIZER_FLAG="-DEXECUTORCH_USE_SANITIZER=ON"
+  fi
+
   cmake . \
     -DCMAKE_INSTALL_PREFIX=cmake-out \
     -DEXECUTORCH_USE_CPP_CODE_COVERAGE=ON \
+    ${SANITIZER_FLAG} \
     -DEXECUTORCH_BUILD_KERNELS_LLM=ON \
     -DEXECUTORCH_BUILD_KERNELS_OPTIMIZED=ON \
     -DEXECUTORCH_BUILD_KERNELS_QUANTIZED=ON \

tools/cmake/preset/default.cmake

@@ -55,6 +55,10 @@ define_overridable_option(
   EXECUTORCH_OPTIMIZE_SIZE
   "Build executorch runtime optimizing for binary size" BOOL OFF
 )
+define_overridable_option(
+  EXECUTORCH_USE_SANITIZER
+  "Build with AddressSanitizer and UndefinedBehaviorSanitizer enabled" BOOL OFF
+)
 define_overridable_option(
   EXECUTORCH_BUILD_ARM_BAREMETAL
   "Build the Arm Baremetal flow for Cortex-M and Ethos-U" BOOL OFF