Correct rationale in simd_x86_64.S comment

The SIMD operations are written in assembly because loading and operating on indeterminate values is UB in C++ but well-defined in assembly. msan not tracking the loads is a side effect, not the reason. Closes #71
Only pass -stdlib=libc++ for c++
2026-08-02 22:25:16 -04:00 · 2026-08-02 21:34:22 -04:00 · 2026-08-02 21:16:27 -04:00 · 2026-08-02 21:06:53 -04:00 · 2026-07-23 15:16:58 -04:00 · 2026-07-23 13:38:56 -04:00
104 changed files with 2335 additions and 269 deletions
@@ -2,62 +2,37 @@ name: CI

 on: [push, pull_request]

+env:
+  CC: clang
+  CXX: clang++
+
 jobs:
-  build-image:
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - runner: ubuntu-latest-amd64
-            arch: amd64
-          - runner: ubuntu-latest-arm64
-            arch: arm64
-    runs-on: ${{ matrix.runner }}
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Log in to registry
-        env:
-          REGISTRY_USER: ${{ secrets.REGISTRY_USER }}
-          REGISTRY_TOKEN: ${{ secrets.REGISTRY_TOKEN }}
-        run: |
-          echo "$REGISTRY_TOKEN" \
-            | docker login -u "$REGISTRY_USER" --password-stdin git.weaselab.dev
-
-      - name: Build and push image if changed
-        run: |
-          image=git.weaselab.dev/weaselab/conflict-set-ci
-          hash="$(sha256sum Dockerfile .pre-commit-config.yaml | sha256sum | cut -c 1-16)"
-          latest="$image:latest-${{ matrix.arch }}"
-          current="$(docker buildx imagetools inspect "$latest" \
-            --format '{{index .Image.Config.Labels "dev.weaselab.ci-hash"}}' 2> /dev/null || true)"
-          if [ "$current" = "$hash" ]; then
-            echo "$latest is up to date"
-          else
-            docker build --push --label "dev.weaselab.ci-hash=$hash" -t "$latest" .
-          fi
-
  pre-commit:
-    needs: build-image
    runs-on: ubuntu-latest-amd64
-    container:
-      image: git.weaselab.dev/weaselab/conflict-set-ci:latest-amd64
-      credentials:
-        username: ${{ secrets.REGISTRY_USER }}
-        password: ${{ secrets.REGISTRY_TOKEN }}
    steps:
      - uses: actions/checkout@v4

+      - uses: actions/cache@v4
+        with:
+          path: /var/cache/apt/archives
+          key: apt-amd64-${{ hashFiles('.gitea/workflows/ci.yml') }}
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y git nodejs pre-commit
+
+      - uses: actions/cache@v4
+        with:
+          path: ~/.cache/pre-commit
+          key: pre-commit-${{ hashFiles('.pre-commit-config.yaml') }}
+
      - name: Run pre-commit
-        env:
-          # use the hooks pre-installed in the image
-          HOME: /tmp
        run: |
          git config --global --add safe.directory "$PWD"
          pre-commit run --all-files --show-diff-on-failure

  test:
-    needs: build-image
    strategy:
      fail-fast: false
      matrix:
@@ -65,26 +40,48 @@ jobs:
          - name: 64-bit-versions
            cmake_args: -DCMAKE_CXX_FLAGS=-DUSE_64_BIT=1
          - name: debug
-            cmake_args: -DCMAKE_BUILD_TYPE=Debug
+            cmake_args: -DCMAKE_BUILD_TYPE=Debug -DMSAN_TOOLCHAIN_PATH=/opt/msan
          - name: simd-fallback
            cmake_args: -DUSE_SIMD_FALLBACK=ON
          - name: gcc
            cmake_args: -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++
    runs-on: ubuntu-latest-amd64
-    container:
-      image: git.weaselab.dev/weaselab/conflict-set-ci:latest-amd64
-      credentials:
-        username: ${{ secrets.REGISTRY_USER }}
-        password: ${{ secrets.REGISTRY_TOKEN }}
    steps:
      - uses: actions/checkout@v4

      - uses: actions/cache@v4
        with:
-          path: .ccache
-          key: ccache-${{ matrix.name }}-${{ gitea.sha }}
-          restore-keys: |
-            ccache-${{ matrix.name }}-
+          path: /var/cache/apt/archives
+          key: apt-amd64-${{ hashFiles('.gitea/workflows/ci.yml') }}
+
+      - name: Install common dependencies
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y \
+            build-essential ccache cmake gcc g++ libc6-dbg \
+            ninja-build python3 valgrind zstd
+          sudo curl -Ls "https://minio.weaselab.dev/public/$(uname -m)/mc.RELEASE.2025-08-13T08-35-41Z" \
+            -o /usr/local/bin/mc && sudo chmod +x /usr/local/bin/mc
+
+      - name: Install LLVM toolchain
+        if: matrix.name != 'gcc'
+        run: |
+          . /etc/os-release
+          wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
+          echo "deb http://apt.llvm.org/${VERSION_CODENAME}/ llvm-toolchain-${VERSION_CODENAME}-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
+          sudo apt-get update -qq
+          sudo apt-get install -y \
+            clang-21 llvm-21 lld-21 mold
+          for tool in clang clang++ llvm-ar llvm-nm llvm-ranlib llvm-objcopy llvm-cov llvm-symbolizer lld ld.lld; do
+            sudo update-alternatives --install /usr/bin/${tool} ${tool} /usr/bin/${tool}-21 100
+          done
+
+      - name: Download MSan toolchain
+        if: matrix.name == 'debug'
+        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: |
@@ -120,24 +117,49 @@ jobs:
            | tee -a "$GITHUB_STEP_SUMMARY"

  release:
-    needs: build-image
    strategy:
      fail-fast: false
      matrix:
        include:
          - runner: ubuntu-latest-amd64
            arch: amd64
+            cmake_args: -DMSAN_TOOLCHAIN_PATH=/opt/msan
          - runner: ubuntu-latest-arm64
            arch: arm64
+            cmake_args: ""
    runs-on: ${{ matrix.runner }}
-    container:
-      image: git.weaselab.dev/weaselab/conflict-set-ci:latest-${{ matrix.arch }}
-      credentials:
-        username: ${{ secrets.REGISTRY_USER }}
-        password: ${{ secrets.REGISTRY_TOKEN }}
    steps:
      - uses: actions/checkout@v4

+      - uses: actions/cache@v4
+        with:
+          path: /var/cache/apt/archives
+          key: apt-${{ matrix.arch }}-${{ hashFiles('.gitea/workflows/ci.yml') }}
+
+      - name: Install dependencies
+        run: |
+          . /etc/os-release
+          wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
+          echo "deb http://apt.llvm.org/${VERSION_CODENAME}/ llvm-toolchain-${VERSION_CODENAME}-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
+          sudo apt-get update -qq
+          sudo apt-get install -y \
+            build-essential ccache clang-21 cmake devscripts \
+            libc6-dbg llvm-21 lld-21 mold ninja-build rpm \
+            valgrind zstd
+          sudo curl -Ls "https://minio.weaselab.dev/public/$(uname -m)/mc.RELEASE.2025-08-13T08-35-41Z" \
+            -o /usr/local/bin/mc && sudo chmod +x /usr/local/bin/mc
+          for tool in clang clang++ llvm-ar llvm-nm llvm-ranlib llvm-objcopy llvm-cov llvm-symbolizer lld ld.lld; do
+            sudo update-alternatives --install /usr/bin/${tool} ${tool} /usr/bin/${tool}-21 100
+          done
+
+      - name: Install paper build dependencies
+        if: matrix.arch == 'amd64'
+        run: |
+          sudo apt-get install -y \
+            biber latexmk \
+            texlive-bibtex-extra texlive-fonts-recommended \
+            texlive-latex-extra texlive-pictures
+
      - uses: actions/cache@v4
        with:
          path: .ccache
@@ -145,11 +167,18 @@ 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

@@ -188,9 +217,6 @@ jobs:
          dest="minio/jenkins/conflict-set/${{ gitea.run_number }}/release-${{ matrix.arch }}/"
          zstd build/Testing/*/Test.xml
          mc cp build/Testing/*/Test.xml.zst "$dest"
-          # This step runs even when a previous step failed, to upload test
-          # results. The packages may never have been built though, so skip
-          # them if they're missing.
          if compgen -G "build/*.deb" > /dev/null; then
            mc cp build/*.deb "$dest"
          fi
@@ -209,16 +235,30 @@ jobs:
            | tee -a "$GITHUB_STEP_SUMMARY"

  coverage:
-    needs: build-image
    runs-on: ubuntu-latest-amd64
-    container:
-      image: git.weaselab.dev/weaselab/conflict-set-ci:latest-amd64
-      credentials:
-        username: ${{ secrets.REGISTRY_USER }}
-        password: ${{ secrets.REGISTRY_TOKEN }}
    steps:
      - uses: actions/checkout@v4

+      - uses: actions/cache@v4
+        with:
+          path: /var/cache/apt/archives
+          key: apt-amd64-${{ hashFiles('.gitea/workflows/ci.yml') }}
+
+      - name: Install dependencies
+        run: |
+          . /etc/os-release
+          wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
+          echo "deb http://apt.llvm.org/${VERSION_CODENAME}/ llvm-toolchain-${VERSION_CODENAME}-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
+          sudo apt-get update -qq
+          sudo apt-get install -y \
+            build-essential ccache clang-21 cmake gcovr \
+            libc6-dbg llvm-21 lld-21 mold ninja-build python3 valgrind zstd
+          sudo curl -Ls "https://minio.weaselab.dev/public/$(uname -m)/mc.RELEASE.2025-08-13T08-35-41Z" \
+            -o /usr/local/bin/mc && sudo chmod +x /usr/local/bin/mc
+          for tool in clang clang++ llvm-ar llvm-nm llvm-ranlib llvm-objcopy llvm-cov llvm-symbolizer lld ld.lld; do
+            sudo update-alternatives --install /usr/bin/${tool} ${tool} /usr/bin/${tool}-21 100
+          done
+
      - uses: actions/cache@v4
        with:
          path: .ccache
@@ -37,15 +37,16 @@ ConflictSet::ReadRange singleton(Arena &arena, TrivialSpan key) {
 }

 ConflictSet::ReadRange prefixRange(Arena &arena, TrivialSpan key) {
-  int index;
-  for (index = key.size() - 1; index >= 0; index--)
-    if ((key[index]) != 255)
+  int index = key.size() - 1;
+  for (; index >= 0; index--)
+    if (key[index] != 255)
      break;

  // Must not be called with a string that consists only of zero or more '\xff'
-  // bytes.
+  // bytes, or with an empty string (which has no finite upper bound).
  if (index < 0) {
    assert(false);
+    std::abort();
  }

  uint8_t *buf = new (arena) uint8_t[index + 1];
@@ -1,11 +1,11 @@
 cmake_minimum_required(VERSION 3.18)
 project(
  conflict-set
-  VERSION 0.0.14
+  VERSION 0.1.0
  DESCRIPTION
    "A data structure for optimistic concurrency control on ranges of bitwise-lexicographically-ordered keys."
  HOMEPAGE_URL "https://git.weaselab.dev/weaselab/conflict-set"
-  LANGUAGES C CXX)
+  LANGUAGES C CXX ASM)
 set(CMAKE_CXX_STANDARD 20)

 file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/version.txt ${PROJECT_VERSION})
@@ -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)
@@ -123,7 +130,15 @@ endif()

 set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "")

-add_library(${PROJECT_NAME}-object OBJECT ConflictSet.cpp)
+# Architecture-specific SIMD assembly. These functions operate on
+# potentially-indeterminate memory, which is UB in C++ but well-defined in
+# assembly.
+set(SIMD_ASM_FILES)
+if(CMAKE_SYSTEM_PROCESSOR STREQUAL x86_64 AND NOT USE_SIMD_FALLBACK)
+  set(SIMD_ASM_FILES ${CMAKE_CURRENT_SOURCE_DIR}/simd_x86_64.S)
+endif()
+
+add_library(${PROJECT_NAME}-object OBJECT ConflictSet.cpp ${SIMD_ASM_FILES})
 target_compile_options(${PROJECT_NAME}-object PRIVATE -fno-exceptions
                                                      -fvisibility=hidden)
 target_include_directories(${PROJECT_NAME}-object
@@ -139,6 +154,7 @@ add_custom_command(
  COMMAND_EXPAND_LISTS)

 add_library(${PROJECT_NAME} SHARED ${CMAKE_BINARY_DIR}/${PROJECT_NAME}.o)
+add_dependencies(${PROJECT_NAME} ${PROJECT_NAME}-object)
 set_target_properties(
  ${PROJECT_NAME} PROPERTIES LIBRARY_OUTPUT_DIRECTORY
                             "${CMAKE_CURRENT_BINARY_DIR}/radix_tree")
@@ -155,6 +171,7 @@ if(HAS_VERSION_SCRIPT)
 endif()

 add_library(${PROJECT_NAME}-static STATIC ${CMAKE_BINARY_DIR}/${PROJECT_NAME}.o)
+add_dependencies(${PROJECT_NAME}-static ${PROJECT_NAME}-object)
 if(CMAKE_BUILD_TYPE STREQUAL Debug)
  set_target_properties(${PROJECT_NAME}-static PROPERTIES LINKER_LANGUAGE CXX)
 else()
@@ -224,7 +241,7 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
  endif()

  # ad hoc testing
-  add_executable(conflict_set_main ConflictSet.cpp)
+  add_executable(conflict_set_main ConflictSet.cpp ${SIMD_ASM_FILES})
  target_include_directories(conflict_set_main
                             PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include)
  target_compile_definitions(conflict_set_main PRIVATE ENABLE_MAIN)
@@ -240,7 +257,7 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
    cmake_pop_check_state()

    if(HAS_LIB_FUZZER)
-      add_executable(conflict_set_fuzz_test ConflictSet.cpp)
+      add_executable(conflict_set_fuzz_test ConflictSet.cpp ${SIMD_ASM_FILES})
      target_include_directories(conflict_set_fuzz_test
                                 PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include)
      target_compile_definitions(conflict_set_fuzz_test PRIVATE ENABLE_FUZZ)
@@ -251,8 +268,9 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
    endif()
  endif()

-  # whitebox tests
-  add_executable(fuzz_driver ConflictSet.cpp FuzzTestDriver.cpp)
+  # whitebox tests asan+ubsan
+  add_executable(fuzz_driver ConflictSet.cpp FuzzTestDriver.cpp
+                             ${SIMD_ASM_FILES})
  target_compile_options(fuzz_driver PRIVATE ${TEST_FLAGS})
  if(NOT CMAKE_CROSSCOMPILING)
    target_compile_options(fuzz_driver PRIVATE -fsanitize=address,undefined)
@@ -266,9 +284,39 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
    add_test(NAME conflict_set_fuzz_${hash} COMMAND fuzz_driver ${TEST})
  endforeach()

+  # whitebox tests msan
+  if(MSAN_TOOLCHAIN_PATH)
+    add_executable(fuzz_driver_msan ConflictSet.cpp FuzzTestDriver.cpp
+                                    ${SIMD_ASM_FILES})
+    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
+                $<$<COMPILE_LANGUAGE:CXX>:-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)
+    add_executable(tsan_driver ConflictSet.cpp FuzzTestDriver.cpp
+                               ${SIMD_ASM_FILES})
    target_compile_options(tsan_driver PRIVATE ${TEST_FLAGS} -fsanitize=thread)
    target_link_options(tsan_driver PRIVATE -fsanitize=thread)
    target_compile_definitions(tsan_driver PRIVATE ENABLE_FUZZ THREAD_TEST)
@@ -383,13 +431,25 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
  if(NOT CMAKE_CROSSCOMPILING)
    find_program(HARDENING_CHECK hardening-check)
    if(HARDENING_CHECK)
+      # Not all versions of hardening-check support the same options, so query
+      # the help output before using architecture-specific skips.
+      execute_process(
+        COMMAND ${HARDENING_CHECK} --help
+        OUTPUT_VARIABLE hardening_check_help
+        ERROR_VARIABLE hardening_check_help
+        OUTPUT_STRIP_TRAILING_WHITESPACE ERROR_STRIP_TRAILING_WHITESPACE)
+      set(hardening_check_arch_flags "")
      # Control flow integrity (CET) is x86-only and branch protection (PAC/BTI)
      # is arm64-only, so ignore whichever doesn't apply.
      if(CMAKE_SYSTEM_PROCESSOR STREQUAL aarch64 OR CMAKE_SYSTEM_PROCESSOR
                                                    STREQUAL arm64)
-        set(hardening_check_arch_flags --nocfprotection)
+        if(hardening_check_help MATCHES "nocfprotection")
+          list(APPEND hardening_check_arch_flags --nocfprotection)
+        endif()
      else()
-        set(hardening_check_arch_flags --nobranchprotection)
+        if(hardening_check_help MATCHES "nobranchprotection")
+          list(APPEND hardening_check_arch_flags --nobranchprotection)
+        endif()
      endif()
      add_test(
        NAME hardening_check
@@ -28,6 +28,7 @@ limitations under the License.
 #include "Internal.h"
 #include "LongestCommonPrefix.h"
 #include "Metrics.h"
+#include "simd.h"

 #include <algorithm>
 #include <bit>
@@ -910,34 +911,11 @@ int getNodeIndexExists(Node3 *self, uint8_t index) {

 int getNodeIndex(Node16 *self, uint8_t index) {

-#ifdef HAS_AVX
-  // Based on https://www.the-paper-trail.org/post/art-paper-notes/
-
-  // key_vec is 16 repeated copies of the searched-for byte, one for every
-  // possible position in child_keys that needs to be searched.
-  __m128i key_vec = _mm_set1_epi8(index);
-
-  // Compare all child_keys to 'index' in parallel. Don't worry if some of the
-  // keys aren't valid, we'll mask the results to only consider the valid ones
-  // below.
-  __m128i indices;
-  memcpy(&indices, self->index, Node16::kMaxNodes);
-  __m128i results = _mm_cmpeq_epi8(key_vec, indices);
-
-  // Build a mask to select only the first node->num_children values from the
-  // comparison (because the other values are meaningless)
-  uint32_t mask = (1 << self->numChildren) - 1;
-
-  // Change the results of the comparison into a bitfield, masking off any
-  // invalid comparisons.
-  uint32_t bitfield = _mm_movemask_epi8(results) & mask;
-
-  // No match if there are no '1's in the bitfield.
+#if defined(__x86_64__) && !defined(USE_SIMD_FALLBACK)
+  uint32_t bitfield =
+      find_eq_16(self->index, index) & ((1 << self->numChildren) - 1);
  if (bitfield == 0)
    return -1;
-
-  // Find the index of the first '1' in the bitfield by counting the leading
-  // zeros.
  return std::countr_zero(bitfield);
 #elif defined(HAS_ARM_NEON)
  // Based on
@@ -970,13 +948,9 @@ int getNodeIndex(Node16 *self, uint8_t index) {

 int getNodeIndexExists(Node16 *self, uint8_t index) {

-#ifdef HAS_AVX
-  __m128i key_vec = _mm_set1_epi8(index);
-  __m128i indices;
-  memcpy(&indices, self->index, Node16::kMaxNodes);
-  __m128i results = _mm_cmpeq_epi8(key_vec, indices);
-  uint32_t mask = (1 << self->numChildren) - 1;
-  uint32_t bitfield = _mm_movemask_epi8(results) & mask;
+#if defined(__x86_64__) && !defined(USE_SIMD_FALLBACK)
+  uint32_t bitfield =
+      find_eq_16(self->index, index) & ((1 << self->numChildren) - 1);
  assume(bitfield != 0);
  return std::countr_zero(bitfield);
 #elif defined(HAS_ARM_NEON)
@@ -1266,13 +1240,9 @@ TaggedNodePointer getChildGeq(Node16 *self, int child) {
    return nullptr;
  }

-#ifdef HAS_AVX
-  __m128i key_vec = _mm_set1_epi8(child);
-  __m128i indices;
-  memcpy(&indices, self->index, Node16::kMaxNodes);
-  __m128i results = _mm_cmpeq_epi8(key_vec, _mm_min_epu8(key_vec, indices));
-  int mask = (1 << self->numChildren) - 1;
-  uint32_t bitfield = _mm_movemask_epi8(results) & mask;
+#if defined(__x86_64__) && !defined(USE_SIMD_FALLBACK)
+  uint32_t bitfield =
+      find_ge_16(self->index, child) & ((1 << self->numChildren) - 1);
  return bitfield == 0 ? nullptr : self->children[std::countr_zero(bitfield)];
 #elif defined(HAS_ARM_NEON)
  uint8x16_t indices;
@@ -1332,8 +1302,8 @@ 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) {
@@ -2130,13 +2100,9 @@ bool scan16(const InternalVersionT *vs, const uint8_t *is, int begin, int end,

  return !(compared & mask);

-#elif defined(HAS_AVX)
+#elif defined(__x86_64__) && !defined(USE_SIMD_FALLBACK)

-  __m128i indices;
-  memcpy(&indices, is, 16);
-  indices = _mm_sub_epi8(indices, _mm_set1_epi8(begin));
-  uint32_t mask = ~_mm_movemask_epi8(_mm_cmpeq_epi8(
-      indices, _mm_max_epu8(indices, _mm_set1_epi8(end - begin))));
+  uint32_t mask = mask_in_range_16(is, begin, end);

  uint32_t compared = 0;
  if constexpr (kAVX512) {
@@ -2153,12 +2119,14 @@ bool scan16(const InternalVersionT *vs, const uint8_t *is, int begin, int end,
  auto inBounds = [&](unsigned c) { return c - shiftAmount < shiftUpperBound; };

  uint32_t compared = 0;
-  for (int i = 0; i < 16; ++i) {
-    compared |= (vs[i] > readVersion) << i;
-  }
  uint32_t mask = 0;
  for (int i = 0; i < 16; ++i) {
-    mask |= inBounds(is[i]) << i;
+    if (vs[i] > readVersion) {
+      compared |= 1u << i;
+      if (inBounds(is[i])) {
+        mask |= 1u << i;
+      }
+    }
  }
  return !(compared & mask);

@@ -2250,17 +2218,9 @@ bool checkMaxBetweenExclusiveImpl(Node3 *n, int begin, int end,
  auto inBounds = [&](unsigned c) { return c - shiftAmount < shiftUpperBound; };

  uint32_t mask = 0;
-  for (int i = 0; i < Node3::kMaxNodes; ++i) {
+  for (int i = 0; i < self->numChildren; ++i) {
    mask |= inBounds(self->index[i]) << i;
  }
-  mask &= (1 << self->numChildren) - 1;
-#ifdef __aarch64__
-  // The bits surviving the mask above don't derive from uninitialized slots,
-  // but clang 21+ on aarch64 lowers inBounds through flags+csel, which
-  // memcheck models imprecisely, tainting bits the mask provably clears.
-  // https://git.weaselab.dev/weaselab/conflict-set/issues/39
-  VALGRIND_MAKE_MEM_DEFINED(&mask, sizeof(mask));
-#endif
  if (!mask) {
    return true;
  }
@@ -2268,17 +2228,11 @@ bool checkMaxBetweenExclusiveImpl(Node3 *n, int begin, int end,
  const bool firstRangeOk =
      !child->entryPresent || child->entry.rangeVersion <= readVersion;
  uint32_t compared = 0;
-  for (int i = 0; i < Node3::kMaxNodes; ++i) {
+  for (int i = 0; i < self->numChildren; ++i) {
    compared |= (self->childMaxVersion[i] > readVersion) << i;
  }

-  uint32_t compared_masked = compared & mask;
-#ifdef __aarch64__
-  // Same imprecise csel modeling as above.
-  // https://git.weaselab.dev/weaselab/conflict-set/issues/39
-  VALGRIND_MAKE_MEM_DEFINED(&compared_masked, sizeof(compared_masked));
-#endif
-  return !compared_masked && firstRangeOk;
+  return !(compared & mask) && firstRangeOk;
 }

 template <bool kAVX512>
@@ -2344,15 +2298,10 @@ bool checkMaxBetweenExclusiveImpl(Node16 *n, int begin, int end,

  return !(compared & mask) && firstRangeOk;

-#elif defined(HAS_AVX)
+#elif defined(__x86_64__) && !defined(USE_SIMD_FALLBACK)

-  __m128i indices;
-  memcpy(&indices, self->index, 16);
-  indices = _mm_sub_epi8(indices, _mm_set1_epi8(begin));
-  uint32_t mask =
-      0xffff & ~_mm_movemask_epi8(_mm_cmpeq_epi8(
-                   indices, _mm_max_epu8(indices, _mm_set1_epi8(end - begin))));
-  mask &= (1 << self->numChildren) - 1;
+  uint32_t mask = mask_in_range_16(self->index, begin, end) &
+                  ((1 << self->numChildren) - 1);
  if (!mask) {
    return true;
  }
@@ -2375,10 +2324,9 @@ bool checkMaxBetweenExclusiveImpl(Node16 *n, int begin, int end,
  auto inBounds = [&](unsigned c) { return c - shiftAmount < shiftUpperBound; };

  uint32_t mask = 0;
-  for (int i = 0; i < 16; ++i) {
+  for (int i = 0; i < self->numChildren; ++i) {
    mask |= inBounds(self->index[i]) << i;
  }
-  mask &= (1 << self->numChildren) - 1;
  if (!mask) {
    return true;
  }
@@ -2386,7 +2334,7 @@ bool checkMaxBetweenExclusiveImpl(Node16 *n, int begin, int end,
  const bool firstRangeOk =
      !child->entryPresent || child->entry.rangeVersion <= readVersion;
  uint32_t compared = 0;
-  for (int i = 0; i < 16; ++i) {
+  for (int i = 0; i < self->numChildren; ++i) {
    compared |= (self->childMaxVersion[i] > readVersion) << i;
  }
  return !(compared & mask) && firstRangeOk;
@@ -3864,17 +3812,17 @@ PRESERVE_NONE void right_side_iter(Job *job, Context *context) {
 void Job::init(const ConflictSet::ReadRange *read, ConflictSet::Result *result,
               Node *root, int64_t oldestVersionFullPrecision) {
  auto begin = TrivialSpan(read->begin.p, read->begin.len);
-  auto end = TrivialSpan(read->end.p, read->end.len);
  if (read->readVersion < oldestVersionFullPrecision) [[unlikely]] {
    *result = ConflictSet::TooOld;
    continuation = complete;
-  } else if (end.size() == 0) {
+  } else if (read->end.len == 0) {
    this->begin = begin;
    this->n = root;
    this->readVersion = InternalVersionT(read->readVersion);
    this->result = result;
    continuation = check::point_read_state_machine::begin;
  } else {
+    auto end = TrivialSpan(read->end.p, read->end.len);
    this->begin = begin;
    this->end = end;
    this->n = root;
@@ -5046,8 +4994,8 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
      for (int i = 0; i < count; ++i) {
        const auto &w = writes[i];
        auto begin = TrivialSpan(w.begin.p, w.begin.len);
-        auto end = TrivialSpan(w.end.p, w.end.len);
        if (w.end.len > 0) {
+          auto end = TrivialSpan(w.end.p, w.end.len);
          addWriteRange(rootParent->children[0], begin, end,
                        InternalVersionT(writeVersion), &writeContext);
        } else {
@@ -5589,7 +5537,12 @@ ConflictSet::ConflictSet(ConflictSet &&other) noexcept
    : impl(std::exchange(other.impl, nullptr)) {}

 ConflictSet &ConflictSet::operator=(ConflictSet &&other) noexcept {
+  if (this != &other) {
+    if (impl) {
+      internal_destroy(impl);
+    }
    impl = std::exchange(other.impl, nullptr);
+  }
  return *this;
 }

@@ -5674,13 +5627,13 @@ std::string getPartialKeyPrintable(Node *n) {
 }

 std::string strinc(std::string_view str, bool &ok) {
-  int index;
-  for (index = str.size() - 1; index >= 0; index--)
-    if ((uint8_t &)(str[index]) != 255)
+  int index = static_cast<int>(str.size()) - 1;
+  for (; index >= 0; index--)
+    if (static_cast<uint8_t>(str[index]) != 255)
      break;

  // Must not be called with a string that consists only of zero or more
-  // '\xff' bytes.
+  // '\xff' bytes, and the empty string has no successor.
  if (index < 0) {
    ok = false;
    return {};
@@ -5688,7 +5641,8 @@ std::string strinc(std::string_view str, bool &ok) {
  ok = true;

  auto r = std::string(str.substr(0, index + 1));
-  ((uint8_t &)r[r.size() - 1])++;
+  auto &last = r[r.size() - 1];
+  last = static_cast<char>(static_cast<uint8_t>(last) + 1);
  return r;
 }

@@ -1,46 +0,0 @@
-FROM ubuntu:rolling
-
-WORKDIR /tmp
-ENV HOME=/tmp
-RUN chmod -R 777 /tmp
-
-# Install apt dependencies
-RUN apt-get update
-RUN apt-get upgrade -y
-RUN TZ=America/Los_Angeles DEBIAN_FRONTEND=noninteractive apt-get install -y \
-    biber \
-    build-essential \
-    ccache \
-    clang \
-    cmake \
-    curl \
-    devscripts \
-    gcovr \
-    git \
-    latexmk \
-    libc6-dbg \
-    llvm \
-    mold \
-    ninja-build \
-    nodejs \
-    pre-commit \
-    python3-requests \
-    rpm \
-    texlive-bibtex-extra \
-    texlive-fonts-recommended \
-    texlive-latex-extra \
-    texlive-pictures \
-    valgrind \
-    wget \
-    zstd
-
-# MinIO client, for uploading build artifacts
-RUN curl -Ls "https://dl.min.io/client/mc/release/linux-$(dpkg --print-architecture)/mc" \
-    -o /usr/local/bin/mc && chmod +x /usr/local/bin/mc
-
-ENV CC=clang
-ENV CXX=clang++
-
-# Try to have all the pre-commit hooks we'll need already initialized
-COPY .pre-commit-config.yaml /tmp/
-RUN git init && pre-commit install-hooks
@@ -96,7 +96,9 @@ void ConflictSet::setOldestVersion(int64_t oldestVersion) {
  return impl->setOldestVersion(oldestVersion);
 }

-int64_t ConflictSet::getBytes() const { return -1; }
+// The hash_table implementation does not track memory usage, so return 0 to
+// satisfy the API contract that getBytes() returns a non-negative value.
+int64_t ConflictSet::getBytes() const { return 0; }

 void ConflictSet::getMetricsV1(MetricsV1 **metrics, int *count) const {
  *metrics = nullptr;
@@ -119,7 +121,13 @@ ConflictSet::ConflictSet(ConflictSet &&other) noexcept
    : impl(std::exchange(other.impl, nullptr)) {}

 ConflictSet &ConflictSet::operator=(ConflictSet &&other) noexcept {
+  if (this != &other) {
+    if (impl) {
+      impl->~Impl();
+      safe_free(impl, sizeof(Impl));
+    }
    impl = std::exchange(other.impl, nullptr);
+  }
  return *this;
 }

@@ -155,7 +163,10 @@ __attribute__((__visibility__("default"))) void ConflictSet_destroy(void *cs) {
 }
 __attribute__((__visibility__("default"))) int64_t
 ConflictSet_getBytes(void *cs) {
-  using Impl = ConflictSet::Impl;
-  return -1;
+  (void)cs;
+  // The hash_table implementation does not track memory usage, so return 0 to
+  // satisfy the API contract that ConflictSet_getBytes returns a non-negative
+  // value.
+  return 0;
 }
 }
@@ -7,10 +7,10 @@ Hardware for all benchmarks is an AMD Ryzen 9 7900 with (2x32GB) 5600MT/s CL28-3
 ```
 $ clang++ --version

-Ubuntu clang version 20.0.0 (++20241120082228+86734c857724-1~exp1~20241120202359.554)
+Ubuntu clang version 21.1.8 (6ubuntu1)
 Target: x86_64-pc-linux-gnu
 Thread model: posix
-InstalledDir: /usr/lib/llvm-20/bin
+InstalledDir: /usr/lib/llvm-21/bin
 ```

 # Microbenchmark
@@ -19,30 +19,30 @@ InstalledDir: /usr/lib/llvm-20/bin

 |               ns/op |                op/s |    err% |          ins/op |          cyc/op |    IPC |         bra/op |   miss% |     total | benchmark
 |--------------------:|--------------------:|--------:|----------------:|----------------:|-------:|---------------:|--------:|----------:|:----------
-|              161.29 |        6,200,056.17 |    0.1% |        3,014.03 |          831.04 |  3.627 |         504.59 |    0.0% |      1.93 | `point reads`
-|              158.32 |        6,316,160.64 |    0.1% |        2,954.16 |          815.80 |  3.621 |         490.17 |    0.0% |      1.89 | `prefix reads`
-|              237.39 |        4,212,409.50 |    0.2% |        3,592.41 |        1,233.96 |  2.911 |         629.31 |    0.0% |      2.84 | `range reads`
-|              442.11 |        2,261,878.94 |    0.0% |        4,450.57 |        2,314.25 |  1.923 |         707.92 |    2.1% |      5.28 | `point writes`
-|              439.89 |        2,273,308.53 |    0.1% |        4,410.22 |        2,302.29 |  1.916 |         694.74 |    2.1% |      5.25 | `prefix writes`
-|              290.96 |        3,436,936.78 |    0.0% |        2,315.38 |        1,528.68 |  1.515 |         396.69 |    3.3% |      3.49 | `range writes`
-|              476.93 |        2,096,762.02 |    0.6% |        6,999.33 |        2,484.94 |  2.817 |       1,251.73 |    1.3% |      0.06 | `monotonic increasing point writes`
-|          131,736.57 |            7,590.91 |    1.1% |      807,444.50 |      704,941.71 |  1.145 |     144,584.60 |    0.9% |      0.01 | `worst case for radix tree`
-|               45.50 |       21,978,369.95 |    1.1% |          902.00 |          232.36 |  3.882 |         132.00 |    0.0% |      0.01 | `create and destroy`
+|              164.29 |        6,086,873.38 |    0.0% |        3,107.03 |          604.19 |  5.142 |         558.59 |    0.0% |      1.96 | `point reads`
+|              161.05 |        6,209,395.38 |    0.1% |        3,036.76 |          592.21 |  5.128 |         539.35 |    0.0% |      1.93 | `prefix reads`
+|              239.55 |        4,174,539.38 |    0.1% |        3,722.71 |          880.68 |  4.227 |         692.00 |    0.0% |      2.86 | `range reads`
+|              354.75 |        2,818,919.14 |    0.7% |        4,523.64 |        1,304.75 |  3.467 |         720.22 |    2.0% |      4.23 | `point writes`
+|              345.32 |        2,895,878.47 |    0.1% |        4,484.57 |        1,270.31 |  3.530 |         705.00 |    1.8% |      4.12 | `prefix writes`
+|              193.48 |        5,168,547.42 |    0.1% |        2,224.10 |          711.72 |  3.125 |         377.17 |    3.3% |      2.32 | `range writes`
+|              404.89 |        2,469,777.50 |    2.4% |        6,855.96 |        1,489.70 |  4.602 |       1,227.82 |    1.3% |      0.05 | `monotonic increasing point writes`
+|          134,231.80 |            7,449.80 |    1.9% |      812,045.25 |      495,770.40 |  1.638 |     151,246.50 |    0.9% |      0.01 | `worst case for radix tree`
+|               37.80 |       26,454,311.17 |    0.4% |          701.00 |          139.14 |  5.038 |         102.00 |    0.0% |      0.01 | `create and destroy`

 ## Radix tree (this implementation)


 |               ns/op |                op/s |    err% |          ins/op |          cyc/op |    IPC |         bra/op |   miss% |     total | benchmark
 |--------------------:|--------------------:|--------:|----------------:|----------------:|-------:|---------------:|--------:|----------:|:----------
-|               12.36 |       80,885,626.43 |    0.2% |          243.56 |           63.62 |  3.828 |          31.07 |    0.6% |      0.15 | `point reads`
-|               14.18 |       70,502,196.81 |    0.1% |          297.72 |           73.13 |  4.071 |          40.31 |    0.5% |      0.17 | `prefix reads`
-|               33.44 |       29,901,623.04 |    0.1% |          767.90 |          172.42 |  4.454 |         101.32 |    0.2% |      0.40 | `range reads`
-|               19.48 |       51,342,564.70 |    0.3% |          374.45 |          100.43 |  3.728 |          48.92 |    0.5% |      0.23 | `point writes`
-|               37.46 |       26,694,471.44 |    0.1% |          672.00 |          193.14 |  3.479 |         101.28 |    0.3% |      0.45 | `prefix writes`
-|               38.78 |       25,784,784.34 |    0.0% |          738.26 |          199.93 |  3.693 |         111.59 |    0.1% |      0.47 | `range writes`
-|               76.05 |       13,148,995.74 |    0.7% |        1,450.77 |          397.16 |  3.653 |         275.72 |    0.0% |      0.01 | `monotonic increasing point writes`
-|          286,920.33 |            3,485.29 |    0.4% |    4,117,948.00 |    1,521,352.00 |  2.707 |     714,833.00 |    0.1% |      0.01 | `worst case for radix tree`
-|               95.66 |       10,453,798.72 |    0.5% |        1,986.00 |          495.04 |  4.012 |         315.00 |    0.0% |      0.01 | `create and destroy`
+|               12.89 |       77,565,115.56 |    0.1% |          244.55 |           47.43 |  5.155 |          34.21 |    0.6% |      0.15 | `point reads`
+|               15.11 |       66,162,047.76 |    0.1% |          297.79 |           55.60 |  5.356 |          43.23 |    0.4% |      0.18 | `prefix reads`
+|               36.29 |       27,559,358.29 |    0.1% |          783.16 |          133.44 |  5.869 |         109.52 |    0.2% |      0.43 | `range reads`
+|               20.53 |       48,719,405.55 |    0.1% |          381.81 |           75.51 |  5.057 |          51.04 |    0.5% |      0.25 | `point writes`
+|               39.37 |       25,402,042.40 |    0.1% |          685.00 |          144.83 |  4.730 |         106.72 |    0.3% |      0.47 | `prefix writes`
+|               43.78 |       22,843,841.63 |    0.1% |          800.40 |          161.06 |  4.970 |         127.36 |    0.1% |      0.53 | `range writes`
+|               78.37 |       12,760,008.75 |    1.0% |        1,452.61 |          288.24 |  5.040 |         278.69 |    0.1% |      0.01 | `monotonic increasing point writes`
+|          322,885.50 |            3,097.07 |    1.5% |    4,362,382.00 |    1,183,852.00 |  3.685 |     765,301.00 |    0.1% |      0.01 | `worst case for radix tree`
+|               99.99 |       10,000,718.79 |    0.4% |        1,775.00 |          367.93 |  4.824 |         288.00 |    0.0% |      0.01 | `create and destroy`

 # "Real data" test

@@ -51,13 +51,13 @@ Point queries only. Gc ratio is the ratio of time spent doing garbage collection
 ## skip list

 ```
-Check: 4.53508 seconds, 371.81 MB/s, Add: 3.81222 seconds, 150.919 MB/s, Gc ratio: 33.66%, Peak idle memory: 5.61007e+06
+Check: 4.62967 seconds, 352.195 MB/s, Add: 3.34177 seconds, 167.771 MB/s, Gc ratio: 37.9399%, Peak idle memory: 5.51852e+06
 ```

 ## radix tree

 ```
-Check: 0.957735 seconds, 1760.6 MB/s, Add: 1.19942 seconds, 479.678 MB/s, Gc ratio: 38.6069%, Peak idle memory: 2.05667e+06
+Check: 1.00477 seconds, 1622.8 MB/s, Add: 1.21142 seconds, 462.808 MB/s, Gc ratio: 39.4716%, Peak idle memory: 2.0226e+06
 ```

 ## hash table
@@ -65,6 +65,6 @@ Check: 0.957735 seconds, 1760.6 MB/s, Add: 1.19942 seconds, 479.678 MB/s, Gc rat
 (The hash table implementation doesn't work on range queries, and its purpose is to provide an idea of how fast point queries can be)

 ```
-Check: 0.804598 seconds, 2095.69 MB/s, Add: 0.671221 seconds, 857.147 MB/s, Gc ratio: 35.0034%, Peak idle memory: 0
+Check: 0.854254 seconds, 1908.74 MB/s, Add: 0.632626 seconds, 886.232 MB/s, Gc ratio: 41.0827%, Peak idle memory: 0
 ```

@@ -1,5 +1,6 @@
 #include <ConflictSet.h>

+#include <algorithm>
 #include <cerrno>
 #include <chrono>
 #include <cstdio>
@@ -77,10 +78,10 @@ int main(int argc, const char **argv) {
      begin = end + 1;
      end = (uint8_t *)memchr(begin, '\n', size);

-      if (line.size() > 0 && line[0] == 'P') {
-        write = line.subspan(2, line.size());
-      } else if (line.size() > 0 && line[0] == 'L') {
-        reads.push_back(line.subspan(2, line.size()));
+      if (line.size() >= 2 && line[0] == 'P') {
+        write = line.subspan(2, line.size() - 2);
+      } else if (line.size() >= 2 && line[0] == 'L') {
+        reads.push_back(line.subspan(2, line.size() - 2));
      } else if (line.empty()) {
        {
          readRanges.resize(reads.size());
@@ -90,7 +91,7 @@ int main(int argc, const char **argv) {
            iter->begin.len = read.size();
            checkBytes += read.size();
            iter->end.len = 0;
-            iter->readVersion = version - 100;
+            iter->readVersion = std::max<int64_t>(0, version - 100);
            ++iter;
          }
        }
@@ -121,7 +122,7 @@ int main(int argc, const char **argv) {
        }

        timer = now();
-        cs.setOldestVersion(version - 10000);
+        cs.setOldestVersion(std::max<int64_t>(0, version - 10000));
        gcTime += now() - timer;
      }
    }
@@ -12,6 +12,7 @@
 #include <sys/ioctl.h>
 #include <sys/resource.h>
 #include <sys/socket.h>
+#include <sys/syscall.h>
 #include <sys/types.h>
 #include <sys/uio.h>
 #include <thread>
@@ -38,6 +38,9 @@ std::span<const uint8_t> keyAfter(Arena &arena, std::span<const uint8_t> key) {

 std::span<const uint8_t> copyToArena(Arena &arena,
                                     std::span<const uint8_t> key) {
+  if (key.size() == 0) {
+    return std::span<const uint8_t>();
+  }
  auto result = std::span<uint8_t>(new (arena) uint8_t[key.size()], key.size());
  memcpy(result.data(), key.data(), key.size());
  return result;
@@ -97,7 +100,7 @@ force_inline bool getCharacter(const KeyInfo &ki, int character,

 bool operator<(const KeyInfo &lhs, const KeyInfo &rhs) {
  int i = std::min(lhs.key.size(), rhs.key.size());
-  int c = memcmp(lhs.key.data(), rhs.key.data(), i);
+  int c = i > 0 ? memcmp(lhs.key.data(), rhs.key.data(), i) : 0;
  if (c != 0)
    return c < 0;

@@ -287,7 +290,8 @@ private:

  static force_inline bool less(const uint8_t *a, int aLen, const uint8_t *b,
                                int bLen) {
-    int c = memcmp(a, b, std::min(aLen, bLen));
+    int n = std::min(aLen, bLen);
+    int c = n > 0 ? memcmp(a, b, n) : 0;
    if (c < 0)
      return true;
    if (c > 0)
@@ -754,7 +758,8 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {

  void addWrites(const ConflictSet::WriteRange *writes, int count,
                 int64_t writeVersion) {
-    auto points = std::vector<KeyInfo>(count * 2);
+    auto points = std::vector<KeyInfo>();
+    points.reserve(count * 2);
    Arena arena;

    for (int r = 0; r < count; r++) {
@@ -981,7 +986,12 @@ ConflictSet::ConflictSet(ConflictSet &&other) noexcept
    : impl(std::exchange(other.impl, nullptr)) {}

 ConflictSet &ConflictSet::operator=(ConflictSet &&other) noexcept {
+  if (this != &other) {
+    if (impl) {
+      internal_destroy(impl);
+    }
    impl = std::exchange(other.impl, nullptr);
+  }
  return *this;
 }

@@ -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}"
@@ -27,23 +27,37 @@ class Result(enum.Enum):
    TOO_OLD = 2


-def write(begin: bytes, end: Optional[bytes] = None) -> WriteRange:
-    b = (ctypes.c_ubyte * len(begin)).from_buffer(bytearray(begin))
+def _make_key(buf: bytes) -> tuple[_Key, bytearray]:
+    """Create a _Key and a backing bytearray that must be kept alive."""
+    backing = bytearray(buf)
+    array = (ctypes.c_ubyte * len(backing)).from_buffer(backing)
+    return _Key(array, len(array)), backing

+
+def write(begin: bytes, end: Optional[bytes] = None) -> WriteRange:
+    begin_key, begin_buf = _make_key(begin)
    if end is None:
-        e = (ctypes.c_ubyte * 0)()
+        end_key = _Key((ctypes.c_ubyte * 0)(), 0)
+        end_buf = None
    else:
-        e = (ctypes.c_ubyte * len(end)).from_buffer(bytearray(end))
-    return WriteRange(_Key(b, len(b)), _Key(e, len(e)))
+        end_key, end_buf = _make_key(end)
+    result = WriteRange(begin_key, end_key)
+    result._begin_buf = begin_buf
+    result._end_buf = end_buf
+    return result


 def read(version: int, begin: bytes, end: Optional[bytes] = None) -> ReadRange:
-    b = (ctypes.c_ubyte * len(begin)).from_buffer(bytearray(begin))
+    begin_key, begin_buf = _make_key(begin)
    if end is None:
-        e = (ctypes.c_ubyte * 0)()
+        end_key = _Key((ctypes.c_ubyte * 0)(), 0)
+        end_buf = None
    else:
-        e = (ctypes.c_ubyte * len(end)).from_buffer(bytearray(end))
-    return ReadRange(_Key(b, len(b)), _Key(e, len(e)), version)
+        end_key, end_buf = _make_key(end)
+    result = ReadRange(begin_key, end_key, version)
+    result._begin_buf = begin_buf
+    result._end_buf = end_buf
+    return result


 class ConflictSet:
@@ -88,6 +102,7 @@ class ConflictSet:
            ctypes.POINTER(ctypes.c_int),
            ctypes.c_int,
        )
+        self._lib.ConflictSet_check.restype = None

        self._lib.ConflictSet_addWrites.argtypes = (
            ctypes.c_void_p,
@@ -95,13 +110,16 @@ class ConflictSet:
            ctypes.c_int,
            ctypes.c_int64,
        )
+        self._lib.ConflictSet_addWrites.restype = None

        self._lib.ConflictSet_setOldestVersion.argtypes = (
            ctypes.c_void_p,
            ctypes.c_int64,
        )
+        self._lib.ConflictSet_setOldestVersion.restype = None

        self._lib.ConflictSet_destroy.argtypes = (ctypes.c_void_p,)
+        self._lib.ConflictSet_destroy.restype = None

        self._lib.ConflictSet_getBytes.argtypes = (ctypes.c_void_p,)
        self._lib.ConflictSet_getBytes.restype = ctypes.c_int64
--- a/Show More
+++ b/Show More
Author	SHA1	Message	Date
weaselbot	79ae91e7d3	Correct rationale in simd_x86_64.S comment The SIMD operations are written in assembly because loading and operating on indeterminate values is UB in C++ but well-defined in assembly. msan not tracking the loads is a side effect, not the reason. Closes #71	2026-08-02 22:25:16 -04:00
andrew	b19981ee3c	Only pass -stdlib=libc++ for c++	2026-08-02 21:34:22 -04:00
andrew	12650e2132	Update README.md	2026-08-02 21:16:27 -04:00
andrew	6fed133212	Remove UB from indeterminate value handling Move SIMD operations on potentially-indeterminate Node16::index bytes into file-level assembly, where loading and operating on indeterminate values is well-defined (unlike C++). Restructure scalar fallback loops to iterate [0, numChildren) instead of [0, kMaxNodes). Fix TrivialSpan construction from indeterminate pointers in check::Job::init and insertPointWritesOrSorted to only construct when end.len > 0. Add MSan toolchain to the debug CI build to catch these issues going forward.	2026-08-02 21:06:53 -04:00
andrew	9d15af772e	Run msan in CI. Closes #66	2026-07-23 15:16:58 -04:00
andrew	22159c38c5	Add Grafana dashboard for server bench metrics	2026-07-23 13:38:56 -04:00
andrew	8afe5ec75b	Add new coverage to corpus	2026-07-14 14:33:51 -04:00
andrew	6eaa0799d5	Update version This branch is going to be 0.1.x now	2026-07-14 12:26:13 -04:00
andrew	cf783a0cdb	ci: move LaTeX/paper deps to amd64-only release step	2026-07-14 11:57:52 -04:00
andrew	16bd98ab12	Download mc from our minio And remove vestigial dockerfile	2026-07-14 11:54:57 -04:00
andrew	374dcf13b7	ci: trim pre-commit deps; skip LLVM install for gcc matrix	2026-07-14 11:45:05 -04:00
andrew	d96d862cea	Merge pull request 'Fix null pointers passed to memcmp/memcpy in skip_list' (#65 ) from weaselbot/conflict-set:weaselbot/issue-64 into main Reviewed-on: weaselab/conflict-set#65	2026-07-13 21:55:52 +00:00
weaselbot	2231c093df	Fix null pointers passed to memcmp/memcpy in skip_list In addWrites, the sizing constructor std::vector<KeyInfo>(count * 2) was used instead of reserve(count * 2), leaving count*2 default- constructed (null/empty key) entries that were then compared via operator<, passing nullptr to memcmp. Switch to reserve so only real entries exist. Additionally guard the memcmp/memcpy calls in operator<, SkipList::less, and copyToArena against empty spans (where data() may be nullptr), which is reachable on the first setOldestVersion with an empty removal key. Closes #64	2026-07-13 12:04:22 -04:00
andrew	d479f16204	Merge pull request 'Return 0 instead of -1 from hash_table getBytes()' (#63 ) from weaselbot/conflict-set:weaselbot/issue-62 into main Reviewed-on: weaselab/conflict-set#63	2026-07-08 13:58:42 +00:00
weaselbot	dee3a8f640	Return 0 instead of -1 from hash_table getBytes() The hash_table implementation cannot accurately track memory usage and was returning -1 from ConflictSet::getBytes() and ConflictSet_getBytes(). That violates the API contract that getBytes() returns a non-negative byte count. Change both entry points to return 0 and document in ConflictSet.h that implementations which do not track memory usage may return 0. Add a regression test in test_conflict_set.py that loads the hash_table implementation and verifies getBytes() is non-negative. Closes #62	2026-07-07 11:00:52 -04:00
andrew	732d19efa1	Merge pull request 'Fix RealDataBench subspan and version API contract violations' (#61 ) from weaselbot/conflict-set:weaselbot/issue-58 into main Reviewed-on: weaselab/conflict-set#61	2026-06-29 18:49:58 +00:00
andrew	9449190d02	Merge pull request 'Fix undefined behavior on empty input in strinc() and prefixRange()' (#60 ) from weaselbot/conflict-set:weaselbot/issue-59 into main Reviewed-on: weaselab/conflict-set#60	2026-06-29 18:26:04 +00:00
weaselbot	4fcdc5d7e9	Fix RealDataBench subspan and version API contract violations - Use subspan count `line.size() - 2` instead of `line.size()` to avoid reading past the line bounds, and guard lines shorter than the two-byte prefix. - Clamp `readVersion` and `setOldestVersion` arguments to `0` so the conflict set never receives negative, non-monotonic versions during the warmup phase. Fixes #58.	2026-06-29 14:01:23 -04:00
weaselbot	63f9a139da	Fix undefined behavior on empty input in strinc() and prefixRange() strinc() in ConflictSet.cpp used std::string_view::size() (size_t) and subtracted 1 without first checking for an empty string. For the root node, getSearchPath() returns the empty string, so every debug correctness check underflowed size_t and relied on implementation-defined conversion to signed int. prefixRange() in Bench.cpp had the same loop shape. Although TrivialSpan::size() returns int, on an empty (or all-0xff) key the function then asserted and continued executing, allocating a zero-length buffer and writing before its start. Changes: - In strinc(), initialize index as signed int(str.size()) - 1 so the loop is skipped for empty input, and return ok=false cleanly. - In prefixRange(), initialize index the same way and call std::abort() after the assert so invalid input cannot fall through to an out-of-bounds write. - Replace C-style uint8_t casts with explicit static_casts. Closes #59	2026-06-29 13:52:02 -04:00
andrew	8f9f345c64	Merge pull request 'Keep Python wrapper key buffers alive in WriteRange/ReadRange' (#43 ) from weaselbot/conflict-set:weaselbot/issue-42 into main Reviewed-on: weaselab/conflict-set#43 Reviewed-by: andrew <andrew@weaselab.dev>	2026-06-23 01:17:45 +00:00
andrew	b9b2d69dd5	Merge pull request 'Disallow copying ConflictSet in C++98/C++03' (#51 ) from weaselbot/conflict-set:weaselbot/issue-48 into main Reviewed-on: weaselab/conflict-set#51	2026-06-22 23:44:59 +00:00
andrew	d3c8f4afc6	Merge pull request 'Include <sys/syscall.h> in ServerBench.cpp for SYS_perf_event_open' (#44 ) from weaselbot/conflict-set:weaselbot/issue-41 into main Reviewed-on: weaselab/conflict-set#44	2026-06-22 20:01:43 +00:00
andrew	549724f09e	Merge pull request 'Assert return values in test_update_zero_should_commit / conflict' (#50 ) from weaselbot/conflict-set:weaselbot/issue-49 into main Reviewed-on: weaselab/conflict-set#50	2026-06-22 19:29:55 +00:00
andrew	52eb13cc0b	Merge pull request 'Fix CMake Unix Makefiles parallel build race for conflict-set.o' (#52 ) from weaselbot/conflict-set:weaselbot/issue-47 into main Reviewed-on: weaselab/conflict-set#52	2026-06-22 19:08:09 +00:00
andrew	f30887f280	Merge pull request 'Fix move-assignment leak and self-assignment in ConflictSet' (#55 ) from weaselbot/conflict-set:weaselbot/issue-54 into main Reviewed-on: weaselab/conflict-set#55	2026-06-22 18:40:25 +00:00
andrew	ccd637deab	We already know __cplusplus is defined	2026-06-22 14:18:33 -04:00
weaselbotandandrew	971deb477c	Keep Python key buffers alive in WriteRange/ReadRange `write()` and `read()` created _Key objects from ephemeral ctypes arrays backed by local bytearray objects. Once the helpers returned, those local variables were freed, leaving the C library with dangling pointers when addWrites()/check() later read the keys. Store the backing bytearray on the returned WriteRange/ReadRange objects as private `_begin_buf` / `_end_buf` attributes. Python keeps them alive for the lifetime of the range object, so the C pointer is always valid. Closes #42	2026-06-22 14:09:18 -04:00
weaselbotandandrew	ff0722728a	Include <sys/syscall.h> in ServerBench.cpp for SYS_perf_event_open `ServerBench.cpp` calls `syscall(SYS_perf_event_open, ...)` but did not include `<sys/syscall.h>`, relying on `<unistd.h>` to transitively provide the `SYS_*` constants. On toolchains where that does not happen, the build fails with `SYS_perf_event_open` not declared. Add the missing include so `server_bench` compiles on any platform that provides `perf_event_open`. Resolves weaselab/conflict-set#41.	2026-06-22 14:09:14 -04:00
weaselbotandandrew	60881419b8	Assert return values in test_update_zero_should_commit / conflict Add the missing [Result.COMMIT] / [Result.CONFLICT] assertions so that the two regression tests actually verify the expected conflict-set outcome, not just that the calls do not crash.	2026-06-22 14:09:10 -04:00
weaselbotandandrew	4515af3662	CMake: add target-level dependencies for conflict-set-object The custom command that links conflict-set.o depends on $<TARGET_OBJECTS:conflict-set-object>, but that generator expression does not create a target-level dependency. With the Unix Makefiles generator, parallel builds can start building the consuming libraries before the object library's build rule is available, producing: gmake[3]: *** No rule to make target 'CMakeFiles/conflict-set-object.dir/ConflictSet.cpp.o', needed by 'conflict-set.o'. Stop. Add add_dependencies() so that conflict-set and conflict-set-static cannot build until conflict-set-object has produced its object files. Closes #47	2026-06-22 14:09:04 -04:00
weaselbotandandrew	4dc5f7f75c	Fix self-move-assignment and leak in ConflictSet move-assignment The user-declared move-assignment operator overwrote `impl` without first destroying the existing implementation object, leaking all memory and resources owned by the left-hand side. Self-move-assignment also set `impl` to nullptr, leaving the object invalid and leaking the old state. Fix all three implementations (ConflictSet.cpp, SkipList.cpp, HashTable.cpp) to guard against self-assignment and to destroy/free the old `impl` before taking ownership of `other.impl`.	2026-06-22 14:08:59 -04:00
weaselbot	7eaac2a184	Make ConflictSet non-copyable in C++98/C++03 `ConflictSet(const ConflictSet&)` and `operator=(const ConflictSet&)` were only deleted for C++11 and later. In C++98/C++03 the compiler implicitly generated public copy operations, so copying a ConflictSet shared the opaque `Impl*` and caused a double-free on destruction. Declare both operations private and leave them undefined when `__cplusplus <= 199711L`, matching the standard pre-C++11 idiom for move-only types. Guard the declarations with `defined(__cplusplus)` so they are not exposed to C90 compilation units. Closes #48	2026-06-22 13:43:04 -04:00
andrew	e9c904a86b	CMakeLists.txt: don't require hardening-check --help to exit 0 hardening-check --help returns exit code 1, so the previous hardening_check_help_result EQUAL 0 guard skipped parsing the help output entirely. As a result, architecture-specific flags such as --nobranchprotection on x86_64 were never added to the test command. Parse the help output regardless of exit code; the option-string regex checks are sufficient.	2026-06-22 13:05:33 -04:00
andrew	789ae8cbb9	ci: install clang/LLVM 21 in Gitea Actions workflows Switch all CI jobs from the distro-packaged clang to the apt.llvm.org clang-21 / llvm-21 toolchain, and register the versioned binaries as alternatives so that CC/CXX=clang/clang++ and tools like llvm-cov and llvm-objcopy use the newer release automatically.	2026-06-22 12:26:19 -04:00
andrew	d70e6a2455	Merge pull request 'Set restype=None for void-returning C functions' (#53 ) from weaselbot/conflict-set:weaselbot/issue-46 into main Reviewed-on: weaselab/conflict-set#53	2026-06-22 01:12:47 +00:00
andrew	8a5168f232	CMakeLists: only pass hardening-check arch flags the tool supports The amd64 CI runner's hardening-check does not recognize --nobranchprotection, causing the hardening_check test to fail at configure time. Query the tool's help output and only include the architecture-specific skip flags when they are advertised.	2026-06-21 21:07:26 -04:00
weaselbotandandrew	742d920aa1	Set restype=None for void-returning C functions in conflict_set.py ConflictSet_check, ConflictSet_addWrites, ConflictSet_setOldestVersion, and ConflictSet_destroy return void in C, but the Python wrapper left their ctypes restype at the default c_int. Set restype = None for each to match the C API contract and avoid undefined behavior from reading the return register of void functions.	2026-06-21 19:25:27 -04:00
andrew	6d8b939a81	Replace CI Docker image with inline apt installs Drops the build-image job and the private registry dependency entirely. Each job now installs only the packages it needs, caching /var/cache/apt/archives keyed on the workflow file and ~/.cache/pre-commit keyed on .pre-commit-config.yaml.	2026-06-21 19:21:04 -04:00