Run msan in CI. Closes #66

.gitea/workflows/ci.yml

@@ -116,8 +116,10 @@ jobs:
         include:
           - runner: ubuntu-latest-amd64
             arch: amd64
+            cmake_args: -DMSAN_TOOLCHAIN_PATH=/opt/msan
           - runner: ubuntu-latest-arm64
             arch: arm64
+            cmake_args: ""
     runs-on: ${{ matrix.runner }}
     steps:
       - uses: actions/checkout@v4
@@ -158,11 +160,18 @@ jobs:
           restore-keys: |
             ccache-release-${{ matrix.arch }}-
 
+      - name: Download MSan toolchain
+        if: matrix.arch == 'amd64'
+        run: |
+          curl -Ls "https://minio.weaselab.dev/public/x86_64/msan-toolchain-21.1.8.tar.zst" -o /tmp/msan-toolchain.tar.zst
+          sudo mkdir -p /opt/msan
+          sudo tar --zstd -xf /tmp/msan-toolchain.tar.zst -C /opt/msan
+
       - name: Build
         run: |
           export CCACHE_DIR="$GITHUB_WORKSPACE/.ccache"
           rm -rf build
-          cmake -S . -B build -G Ninja -DCMAKE_CXX_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_FLAGS=-DNVALGRIND
+          cmake -S . -B build -G Ninja -DCMAKE_CXX_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_FLAGS=-DNVALGRIND ${{ matrix.cmake_args }}
           ninja -C build
           ccache -s
 

CMakeLists.txt

@@ -103,6 +103,13 @@ option(USE_SIMD_FALLBACK
 
 option(DISABLE_TSAN "Disable TSAN" OFF)
 
+set(MSAN_TOOLCHAIN_PATH
+    ""
+    CACHE
+      PATH
+      "Path to an MSan-instrumented libc++ toolchain. When set, an MSan fuzz_driver target is added. Must contain include/c++/v1 and lib. See build_msan_toolchain.sh to produce one."
+)
+
 # This is encouraged according to
 # https://valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.clientreq
 include_directories(SYSTEM ${CMAKE_CURRENT_SOURCE_DIR}/third_party/valgrind)
@@ -253,7 +260,7 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
     endif()
   endif()
 
-  # whitebox tests
+  # whitebox tests asan+ubsan
   add_executable(fuzz_driver ConflictSet.cpp FuzzTestDriver.cpp)
   target_compile_options(fuzz_driver PRIVATE ${TEST_FLAGS})
   if(NOT CMAKE_CROSSCOMPILING)
@@ -268,6 +275,33 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
     add_test(NAME conflict_set_fuzz_${hash} COMMAND fuzz_driver ${TEST})
   endforeach()
 
+  # whitebox tests msan
+  if(MSAN_TOOLCHAIN_PATH)
+    add_executable(fuzz_driver_msan ConflictSet.cpp FuzzTestDriver.cpp)
+    target_compile_options(fuzz_driver_msan PRIVATE ${TEST_FLAGS})
+    if(NOT CMAKE_CROSSCOMPILING)
+      target_compile_options(
+        fuzz_driver_msan
+        PRIVATE -fsanitize=memory -fsanitize-memory-track-origins=2
+                -stdlib=libc++ -I${MSAN_TOOLCHAIN_PATH}/include/c++/v1)
+      target_link_options(
+        fuzz_driver_msan
+        PRIVATE
+        -fsanitize=memory
+        -fsanitize-memory-track-origins=2
+        -stdlib=libc++
+        -L${MSAN_TOOLCHAIN_PATH}/lib
+        LINKER:-rpath,${MSAN_TOOLCHAIN_PATH}/lib)
+    endif()
+    target_compile_definitions(fuzz_driver_msan PRIVATE ENABLE_FUZZ)
+    target_include_directories(fuzz_driver_msan
+                               PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include)
+    foreach(TEST ${CORPUS_TESTS})
+      get_filename_component(hash ${TEST} NAME)
+      add_test(NAME conflict_set_msan_${hash} COMMAND fuzz_driver_msan ${TEST})
+    endforeach()
+  endif()
+
   # tsan tests
   if(NOT CMAKE_CROSSCOMPILING AND NOT DISABLE_TSAN)
     add_executable(tsan_driver ConflictSet.cpp FuzzTestDriver.cpp)

ConflictSet.cpp

@@ -1332,8 +1332,8 @@ TaggedNodePointer getChildGeq(Node *self, int child) {
 
 TaggedNodePointer getFirstChild(Node0 *) { return nullptr; }
 TaggedNodePointer getFirstChild(Node3 *self) {
-  // Improves scan performance
-  self->children[1].prefetch();
+  // Don't prefetch since self->children[1] might be uninitialized and msan
+  // doesn't like that
   return self->children[0];
 }
 TaggedNodePointer getFirstChild(Node16 *self) {

build_msan_toolchain.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+
+set -euxo pipefail
+
+LLVM_VERSION="${LLVM_VERSION:-21}"
+MSAN_PREFIX="${MSAN_PREFIX:-$PWD/msan}"
+JOBS="${JOBS:-$(nproc)}"
+
+cd /tmp
+rm -rf libcxx-msan
+mkdir libcxx-msan
+cd libcxx-msan
+
+git clone --depth=1 "https://github.com/llvm/llvm-project.git" -b "release/${LLVM_VERSION}.x"
+
+cmake -S llvm-project/runtimes -B build_msan \
+  -DCMAKE_BUILD_TYPE=Release \
+  -DCMAKE_CXX_COMPILER="clang++-${LLVM_VERSION}" \
+  -DCMAKE_C_COMPILER="clang-${LLVM_VERSION}" \
+  -DCMAKE_INSTALL_PREFIX="${MSAN_PREFIX}" \
+  -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind" \
+  -DLLVM_USE_SANITIZER=MemoryWithOrigins
+
+cmake --build build_msan -j"${JOBS}"
+cmake --install build_msan
+
+cmake -S llvm-project/runtimes -B build_nomsan \
+  -DCMAKE_BUILD_TYPE=Release \
+  -DCMAKE_CXX_COMPILER="clang++-${LLVM_VERSION}" \
+  -DCMAKE_C_COMPILER="clang-${LLVM_VERSION}" \
+  -DCMAKE_INSTALL_PREFIX="${MSAN_PREFIX}" \
+  -DLLVM_ENABLE_RUNTIMES="libunwind"
+
+cmake --build build_nomsan -j"${JOBS}"
+cmake --install build_nomsan
+
+VERSION="$(clang-"${LLVM_VERSION}" --version | head -n1 | sed -E 's/.*clang version ([0-9.]+).*/\1/')"
+TARBALL="msan-toolchain-${VERSION}.tar.zst"
+
+tar --zstd -cf "${TARBALL}" -C "${MSAN_PREFIX}" .
+
+TARBALL_PATH="$(pwd)/${TARBALL}"
+echo "Created: ${TARBALL_PATH}"