diff --git a/.clang-tidy b/.clang-tidy
new file mode 100644
index 00000000..9f2baf4c
--- /dev/null
+++ b/.clang-tidy
@@ -0,0 +1,73 @@
+---
+# NOTE there must be no spaces before the '-', so put the comma last.
+# The check bugprone-unchecked-optional-access is also turned off atm
+# because it causes clang-tidy to hang randomly. The tracking issue
+# can be found at https://github.com/llvm/llvm-project/issues/69369.
+#
+# Modified from
+# https://github.com/pytorch/pytorch/blob/main/.clang-tidy
+InheritParentConfig: true
+Checks: '
+bugprone-*,
+-bugprone-easily-swappable-parameters,
+-bugprone-forward-declaration-namespace,
+-bugprone-implicit-widening-of-multiplication-result,
+-bugprone-macro-parentheses,
+-bugprone-lambda-function-name,
+-bugprone-narrowing-conversions,
+-bugprone-reserved-identifier,
+-bugprone-swapped-arguments,
+-bugprone-unchecked-optional-access,
+clang-diagnostic-missing-prototypes,
+cppcoreguidelines-*,
+-cppcoreguidelines-avoid-const-or-ref-data-members,
+-cppcoreguidelines-avoid-do-while,
+-cppcoreguidelines-avoid-magic-numbers,
+-cppcoreguidelines-avoid-non-const-global-variables,
+-cppcoreguidelines-interfaces-global-init,
+-cppcoreguidelines-macro-usage,
+-cppcoreguidelines-narrowing-conversions,
+-cppcoreguidelines-owning-memory,
+-cppcoreguidelines-pro-bounds-array-to-pointer-decay,
+-cppcoreguidelines-pro-bounds-constant-array-index,
+-cppcoreguidelines-pro-bounds-pointer-arithmetic,
+-cppcoreguidelines-pro-type-const-cast,
+-cppcoreguidelines-pro-type-cstyle-cast,
+-cppcoreguidelines-pro-type-reinterpret-cast,
+-cppcoreguidelines-pro-type-static-cast-downcast,
+-cppcoreguidelines-pro-type-union-access,
+-cppcoreguidelines-pro-type-vararg,
+-cppcoreguidelines-special-member-functions,
+-cppcoreguidelines-non-private-member-variables-in-classes,
+-facebook-hte-RelativeInclude,
+hicpp-exception-baseclass,
+hicpp-avoid-goto,
+misc-*,
+-misc-const-correctness,
+-misc-include-cleaner,
+-misc-use-anonymous-namespace,
+-misc-unused-parameters,
+-misc-no-recursion,
+-misc-non-private-member-variables-in-classes,
+-misc-confusable-identifiers,
+modernize-*,
+-modernize-macro-to-enum,
+-modernize-pass-by-value,
+-modernize-return-braced-init-list,
+-modernize-use-auto,
+-modernize-use-default-member-init,
+-modernize-use-using,
+-modernize-use-trailing-return-type,
+-modernize-use-nodiscard,
+performance-*,
+readability-container-size-empty,
+readability-delete-null-pointer,
+readability-duplicate-include
+readability-misplaced-array-index,
+readability-redundant-function-ptr-dereference,
+readability-redundant-smartptr-get,
+readability-simplify-subscript-expr,
+readability-string-compare,
+'
+WarningsAsErrors: '*'
+...
diff --git a/.github/workflows/clang-tidy.yaml b/.github/workflows/clang-tidy.yaml
new file mode 100644
index 00000000..3295fc64
--- /dev/null
+++ b/.github/workflows/clang-tidy.yaml
@@ -0,0 +1,57 @@
+name: clang-tidy
+
+on:
+  push:
+    branches:
+      - master
+      - clang-tidy
+    paths:
+      - 'sherpa-onnx/csrc/**'
+
+  pull_request:
+    branches:
+      - master
+    paths:
+      - 'sherpa-onnx/csrc/**'
+
+  workflow_dispatch:
+
+concurrency:
+  group: clang-tidy-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  clang-tidy:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [3.8]
+      fail-fast: false
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install clang-tidy
+        shell: bash
+        run: |
+          pip install clang-tidy
+
+      - name: Configure
+        shell: bash
+        run: |
+          mkdir build
+          cd build
+          cmake -DSHERPA_ONNX_ENABLE_PYTHON=ON -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ..
+
+      - name: Check with clang-tidy
+        shell: bash
+        run: |
+          cd build
+          make check
diff --git a/.github/workflows/flutter-macos.yaml b/.github/workflows/flutter-macos.yaml
index d92d3087..d148fb04 100644
--- a/.github/workflows/flutter-macos.yaml
+++ b/.github/workflows/flutter-macos.yaml
@@ -184,6 +184,7 @@ jobs:
           path: ./*.tar.bz2
 
       - name: Publish to huggingface
+        if: (github.repository_owner == 'csukuangfj' || github.repository_owner == 'k2-fsa') && github.event_name == 'push' && contains(github.ref, 'refs/tags/') && matrix.build_type == 'Release'
         env:
           HF_TOKEN: ${{ secrets.HF_TOKEN }}
         uses: nick-fields/retry@v3
diff --git a/.github/workflows/flutter-windows-x64.yaml b/.github/workflows/flutter-windows-x64.yaml
index ce4e7456..7dfc197e 100644
--- a/.github/workflows/flutter-windows-x64.yaml
+++ b/.github/workflows/flutter-windows-x64.yaml
@@ -133,6 +133,7 @@ jobs:
         shell: bash
         run: |
           d=$PWD
+          SHERPA_ONNX_VERSION=v$(grep "SHERPA_ONNX_VERSION" ./CMakeLists.txt  | cut -d " " -f 2  | cut -d '"' -f 2)
 
           pushd sherpa-onnx/flutter
           dart pub get
@@ -159,6 +160,7 @@ jobs:
           path: ./*.tar.bz2
 
       - name: Publish to huggingface
+        if: (github.repository_owner == 'csukuangfj' || github.repository_owner == 'k2-fsa') && github.event_name == 'push' && contains(github.ref, 'refs/tags/') && matrix.build_type == 'Release'
         env:
           HF_TOKEN: ${{ secrets.HF_TOKEN }}
         uses: nick-fields/retry@v3
diff --git a/CMakeLists.txt b/CMakeLists.txt
index dedf5276..d474c6aa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -167,7 +167,7 @@ if(SHERPA_ONNX_ENABLE_WASM_KWS)
 endif()
 
 if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 14 CACHE STRING "The C++ version to be used.")
+  set(CMAKE_CXX_STANDARD 17 CACHE STRING "The C++ version to be used.")
 endif()
 set(CMAKE_CXX_EXTENSIONS OFF)
 message(STATUS "C++ Standard version: ${CMAKE_CXX_STANDARD}")
diff --git a/cmake/openfst.cmake b/cmake/openfst.cmake
index 59d4f9fc..77e4c157 100644
--- a/cmake/openfst.cmake
+++ b/cmake/openfst.cmake
@@ -3,18 +3,18 @@
 function(download_openfst)
   include(FetchContent)
 
-  set(openfst_URL  "https://github.com/csukuangfj/openfst/archive/refs/tags/sherpa-onnx-2024-06-13.tar.gz")
-  set(openfst_URL2 "https://hub.nuaa.cf/csukuangfj/openfst/archive/refs/tags/sherpa-onnx-2024-06-13.tar.gz")
-  set(openfst_HASH "SHA256=f10a71c6b64d89eabdc316d372b956c30c825c7c298e2f20c780320e8181ffb6")
+  set(openfst_URL  "https://github.com/csukuangfj/openfst/archive/refs/tags/sherpa-onnx-2024-06-19.tar.gz")
+  set(openfst_URL2 "https://hub.nuaa.cf/csukuangfj/openfst/archive/refs/tags/sherpa-onnx-2024-06-19.tar.gz")
+  set(openfst_HASH "SHA256=5c98e82cc509c5618502dde4860b8ea04d843850ed57e6d6b590b644b268853d")
 
   # If you don't have access to the Internet,
   # please pre-download it
   set(possible_file_locations
-    $ENV{HOME}/Downloads/openfst-sherpa-onnx-2024-06-13.tar.gz
-    ${CMAKE_SOURCE_DIR}/openfst-sherpa-onnx-2024-06-13.tar.gz
-    ${CMAKE_BINARY_DIR}/openfst-sherpa-onnx-2024-06-13.tar.gz
-    /tmp/openfst-sherpa-onnx-2024-06-13.tar.gz
-    /star-fj/fangjun/download/github/openfst-sherpa-onnx-2024-06-13.tar.gz
+    $ENV{HOME}/Downloads/openfst-sherpa-onnx-2024-06-19.tar.gz
+    ${CMAKE_SOURCE_DIR}/openfst-sherpa-onnx-2024-06-19.tar.gz
+    ${CMAKE_BINARY_DIR}/openfst-sherpa-onnx-2024-06-19.tar.gz
+    /tmp/openfst-sherpa-onnx-2024-06-19.tar.gz
+    /star-fj/fangjun/download/github/openfst-sherpa-onnx-2024-06-19.tar.gz
   )
 
   foreach(f IN LISTS possible_file_locations)
diff --git a/sherpa-onnx/csrc/CMakeLists.txt b/sherpa-onnx/csrc/CMakeLists.txt
index bac0499a..16da143f 100644
--- a/sherpa-onnx/csrc/CMakeLists.txt
+++ b/sherpa-onnx/csrc/CMakeLists.txt
@@ -534,3 +534,17 @@ if(SHERPA_ONNX_ENABLE_TESTS)
     sherpa_onnx_add_test(${source})
   endforeach()
 endif()
+
+set(srcs_to_check)
+foreach(s IN LISTS sources)
+  list(APPEND srcs_to_check ${CMAKE_CURRENT_LIST_DIR}/${s})
+endforeach()
+
+# For clang-tidy
+add_custom_target(
+  clang-tidy-check
+  clang-tidy -p ${CMAKE_BINARY_DIR}/compile_commands.json --config-file ${CMAKE_SOURCE_DIR}/.clang-tidy ${srcs_to_check}
+  DEPENDS ${sources})
+
+add_custom_target(check DEPENDS clang-tidy-check)
+
diff --git a/sherpa-onnx/csrc/audio-tagging-label-file.cc b/sherpa-onnx/csrc/audio-tagging-label-file.cc
index ea103299..bd71bcb1 100644
--- a/sherpa-onnx/csrc/audio-tagging-label-file.cc
+++ b/sherpa-onnx/csrc/audio-tagging-label-file.cc
@@ -60,7 +60,7 @@ void AudioTaggingLabels::Init(std::istream &is) {
 
     std::size_t pos{};
     int32_t i = std::stoi(index, &pos);
-    if (index.size() == 0 || pos != index.size()) {
+    if (index.empty() || pos != index.size()) {
       SHERPA_ONNX_LOGE("Invalid line: %s", line.c_str());
       exit(-1);
     }
diff --git a/sherpa-onnx/csrc/base64-decode.cc b/sherpa-onnx/csrc/base64-decode.cc
index b22e443e..5723790f 100644
--- a/sherpa-onnx/csrc/base64-decode.cc
+++ b/sherpa-onnx/csrc/base64-decode.cc
@@ -34,7 +34,7 @@ std::string Base64Decode(const std::string &s) {
     exit(-1);
   }
 
-  int32_t n = s.size() / 4 * 3;
+  int32_t n = static_cast<int32_t>(s.size()) / 4 * 3;
 
   std::string ans;
   ans.reserve(n);
@@ -46,16 +46,16 @@ std::string Base64Decode(const std::string &s) {
     }
 
     int32_t first = (Ord(s[i]) << 2) + ((Ord(s[i + 1]) & 0x30) >> 4);
-    ans.push_back(first);
+    ans.push_back(static_cast<char>(first));
 
     if (i + 2 < static_cast<int32_t>(s.size()) && s[i + 2] != '=') {
       int32_t second =
           ((Ord(s[i + 1]) & 0x0f) << 4) + ((Ord(s[i + 2]) & 0x3c) >> 2);
-      ans.push_back(second);
+      ans.push_back(static_cast<char>(second));
 
       if (i + 3 < static_cast<int32_t>(s.size()) && s[i + 3] != '=') {
         int32_t third = ((Ord(s[i + 2]) & 0x03) << 6) + Ord(s[i + 3]);
-        ans.push_back(third);
+        ans.push_back(static_cast<char>(third));
       }
     }
     i += 4;
diff --git a/sherpa-onnx/csrc/cat.cc b/sherpa-onnx/csrc/cat.cc
index 00da2263..05c40b0c 100644
--- a/sherpa-onnx/csrc/cat.cc
+++ b/sherpa-onnx/csrc/cat.cc
@@ -82,9 +82,9 @@ Ort::Value Cat(OrtAllocator *allocator,
   T *dst = ans.GetTensorMutableData<T>();
 
   for (int32_t i = 0; i != leading_size; ++i) {
-    for (int32_t n = 0; n != static_cast<int32_t>(values.size()); ++n) {
-      auto this_dim = values[n]->GetTensorTypeAndShapeInfo().GetShape()[dim];
-      const T *src = values[n]->GetTensorData<T>();
+    for (auto value : values) {
+      auto this_dim = value->GetTensorTypeAndShapeInfo().GetShape()[dim];
+      const T *src = value->GetTensorData<T>();
       src += i * this_dim * trailing_size;
 
       std::copy(src, src + this_dim * trailing_size, dst);
diff --git a/sherpa-onnx/csrc/circular-buffer.cc b/sherpa-onnx/csrc/circular-buffer.cc
index 4ed66733..ef937cab 100644
--- a/sherpa-onnx/csrc/circular-buffer.cc
+++ b/sherpa-onnx/csrc/circular-buffer.cc
@@ -20,7 +20,7 @@ CircularBuffer::CircularBuffer(int32_t capacity) {
 }
 
 void CircularBuffer::Resize(int32_t new_capacity) {
-  int32_t capacity = buffer_.size();
+  int32_t capacity = static_cast<int32_t>(buffer_.size());
   if (new_capacity <= capacity) {
     SHERPA_ONNX_LOGE("new_capacity (%d) <= original capacity (%d). Skip it.",
                      new_capacity, capacity);
@@ -86,7 +86,7 @@ void CircularBuffer::Resize(int32_t new_capacity) {
 }
 
 void CircularBuffer::Push(const float *p, int32_t n) {
-  int32_t capacity = buffer_.size();
+  int32_t capacity = static_cast<int32_t>(buffer_.size());
   int32_t size = Size();
   if (n + size > capacity) {
     int32_t new_capacity = std::max(capacity * 2, n + size);
@@ -126,7 +126,7 @@ std::vector<float> CircularBuffer::Get(int32_t start_index, int32_t n) const {
     return {};
   }
 
-  int32_t capacity = buffer_.size();
+  int32_t capacity = static_cast<int32_t>(buffer_.size());
 
   if (start_index - head_ + n > size) {
     SHERPA_ONNX_LOGE("Invalid start_index: %d and n: %d. head_: %d, size: %d",
diff --git a/sherpa-onnx/csrc/context-graph.cc b/sherpa-onnx/csrc/context-graph.cc
index ef876b36..336208b1 100644
--- a/sherpa-onnx/csrc/context-graph.cc
+++ b/sherpa-onnx/csrc/context-graph.cc
@@ -67,8 +67,8 @@ void ContextGraph::Build(const std::vector<std::vector<int32_t>> &token_ids,
 std::tuple<float, const ContextState *, const ContextState *>
 ContextGraph::ForwardOneStep(const ContextState *state, int32_t token,
                              bool strict_mode /*= true*/) const {
-  const ContextState *node;
-  float score;
+  const ContextState *node = nullptr;
+  float score = 0;
   if (1 == state->next.count(token)) {
     node = state->next.at(token).get();
     score = node->token_score;
@@ -84,7 +84,10 @@ ContextGraph::ForwardOneStep(const ContextState *state, int32_t token,
     score = node->node_score - state->node_score;
   }
 
-  SHERPA_ONNX_CHECK(nullptr != node);
+  if (!node) {
+    SHERPA_ONNX_LOGE("Some bad things happened.");
+    exit(-1);
+  }
 
   const ContextState *matched_node =
       node->is_end ? node : (node->output != nullptr ? node->output : nullptr);
diff --git a/sherpa-onnx/csrc/endpoint.cc b/sherpa-onnx/csrc/endpoint.cc
index 3a9a424c..afe76fdb 100644
--- a/sherpa-onnx/csrc/endpoint.cc
+++ b/sherpa-onnx/csrc/endpoint.cc
@@ -73,10 +73,15 @@ std::string EndpointConfig::ToString() const {
   return os.str();
 }
 
-bool Endpoint::IsEndpoint(int num_frames_decoded, int trailing_silence_frames,
+bool Endpoint::IsEndpoint(int32_t num_frames_decoded,
+                          int32_t trailing_silence_frames,
                           float frame_shift_in_seconds) const {
-  float utterance_length = num_frames_decoded * frame_shift_in_seconds;
-  float trailing_silence = trailing_silence_frames * frame_shift_in_seconds;
+  float utterance_length =
+      static_cast<float>(num_frames_decoded) * frame_shift_in_seconds;
+
+  float trailing_silence =
+      static_cast<float>(trailing_silence_frames) * frame_shift_in_seconds;
+
   if (RuleActivated(config_.rule1, "rule1", trailing_silence,
                     utterance_length) ||
       RuleActivated(config_.rule2, "rule2", trailing_silence,
diff --git a/sherpa-onnx/csrc/endpoint.h b/sherpa-onnx/csrc/endpoint.h
index 73995840..aea5d7d2 100644
--- a/sherpa-onnx/csrc/endpoint.h
+++ b/sherpa-onnx/csrc/endpoint.h
@@ -64,7 +64,7 @@ class Endpoint {
 
   /// This function returns true if this set of endpointing rules thinks we
   /// should terminate decoding.
-  bool IsEndpoint(int num_frames_decoded, int trailing_silence_frames,
+  bool IsEndpoint(int32_t num_frames_decoded, int32_t trailing_silence_frames,
                   float frame_shift_in_seconds) const;
 
  private:
diff --git a/sherpa-onnx/csrc/jieba-lexicon.cc b/sherpa-onnx/csrc/jieba-lexicon.cc
index bffc1187..1bf64cd5 100644
--- a/sherpa-onnx/csrc/jieba-lexicon.cc
+++ b/sherpa-onnx/csrc/jieba-lexicon.cc
@@ -103,6 +103,7 @@ class JiebaLexicon::Impl {
 
       if (w == "。" || w == "！" || w == "？" || w == "，") {
         ans.push_back(std::move(this_sentence));
+        this_sentence = {};
       }
     }  // for (const auto &w : words)
 
diff --git a/sherpa-onnx/csrc/keyword-spotter.cc b/sherpa-onnx/csrc/keyword-spotter.cc
index 7e93d7a0..1110ee58 100644
--- a/sherpa-onnx/csrc/keyword-spotter.cc
+++ b/sherpa-onnx/csrc/keyword-spotter.cc
@@ -4,9 +4,8 @@
 
 #include "sherpa-onnx/csrc/keyword-spotter.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <fstream>
 #include <iomanip>
 #include <memory>
diff --git a/sherpa-onnx/csrc/lexicon.cc b/sherpa-onnx/csrc/lexicon.cc
index 3a502c24..91307a21 100644
--- a/sherpa-onnx/csrc/lexicon.cc
+++ b/sherpa-onnx/csrc/lexicon.cc
@@ -82,7 +82,7 @@ std::unordered_map<std::string, int32_t> ReadTokens(std::istream &is) {
   std::string line;
 
   std::string sym;
-  int32_t id;
+  int32_t id = -1;
   while (std::getline(is, line)) {
     std::istringstream iss(line);
     iss >> sym;
@@ -254,6 +254,7 @@ std::vector<std::vector<int64_t>> Lexicon::ConvertTextToTokenIdsChinese(
           this_sentence.push_back(eos);
         }
         ans.push_back(std::move(this_sentence));
+        this_sentence = {};
 
         if (sil != -1) {
           this_sentence.push_back(sil);
@@ -324,6 +325,7 @@ std::vector<std::vector<int64_t>> Lexicon::ConvertTextToTokenIdsNotChinese(
       if (w != ",") {
         this_sentence.push_back(blank);
         ans.push_back(std::move(this_sentence));
+        this_sentence = {};
       }
 
       continue;
diff --git a/sherpa-onnx/csrc/lexicon.h b/sherpa-onnx/csrc/lexicon.h
index e26a2dec..81a51095 100644
--- a/sherpa-onnx/csrc/lexicon.h
+++ b/sherpa-onnx/csrc/lexicon.h
@@ -62,8 +62,8 @@ class Lexicon : public OfflineTtsFrontend {
   std::unordered_map<std::string, std::vector<int32_t>> word2ids_;
   std::unordered_set<std::string> punctuations_;
   std::unordered_map<std::string, int32_t> token2id_;
-  Language language_;
-  bool debug_;
+  Language language_ = Language::kUnknown;
+  bool debug_ = false;
 };
 
 }  // namespace sherpa_onnx
diff --git a/sherpa-onnx/csrc/offline-ct-transformer-model.cc b/sherpa-onnx/csrc/offline-ct-transformer-model.cc
index 7f7e63b0..2ce593b3 100644
--- a/sherpa-onnx/csrc/offline-ct-transformer-model.cc
+++ b/sherpa-onnx/csrc/offline-ct-transformer-model.cc
@@ -67,7 +67,7 @@ class OfflineCtTransformerModel::Impl {
     std::vector<std::string> tokens;
     SHERPA_ONNX_READ_META_DATA_VEC_STRING_SEP(tokens, "tokens", "|");
 
-    int32_t vocab_size;
+    int32_t vocab_size = 0;
     SHERPA_ONNX_READ_META_DATA(vocab_size, "vocab_size");
     if (static_cast<int32_t>(tokens.size()) != vocab_size) {
       SHERPA_ONNX_LOGE("tokens.size() %d != vocab_size %d",
diff --git a/sherpa-onnx/csrc/offline-ctc-model.cc b/sherpa-onnx/csrc/offline-ctc-model.cc
index cfa8ab45..bd646ece 100644
--- a/sherpa-onnx/csrc/offline-ctc-model.cc
+++ b/sherpa-onnx/csrc/offline-ctc-model.cc
@@ -19,7 +19,7 @@
 
 namespace {
 
-enum class ModelType {
+enum class ModelType : std::uint8_t {
   kEncDecCTCModelBPE,
   kEncDecHybridRNNTCTCBPEModel,
   kTdnn,
diff --git a/sherpa-onnx/csrc/offline-stream.cc b/sherpa-onnx/csrc/offline-stream.cc
index 6e72a4a1..79bdb5c5 100644
--- a/sherpa-onnx/csrc/offline-stream.cc
+++ b/sherpa-onnx/csrc/offline-stream.cc
@@ -4,11 +4,11 @@
 
 #include "sherpa-onnx/csrc/offline-stream.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <cmath>
 #include <iomanip>
+#include <utility>
 
 #include "kaldi-native-fbank/csrc/online-feature.h"
 #include "sherpa-onnx/csrc/macros.h"
@@ -56,7 +56,7 @@ class OfflineStream::Impl {
  public:
   explicit Impl(const FeatureExtractorConfig &config,
                 ContextGraphPtr context_graph)
-      : config_(config), context_graph_(context_graph) {
+      : config_(config), context_graph_(std::move(context_graph)) {
     if (config.is_mfcc) {
       mfcc_opts_.frame_opts.dither = config_.dither;
       mfcc_opts_.frame_opts.snip_edges = config_.snip_edges;
@@ -266,7 +266,7 @@ class OfflineStream::Impl {
 
 OfflineStream::OfflineStream(const FeatureExtractorConfig &config /*= {}*/,
                              ContextGraphPtr context_graph /*= nullptr*/)
-    : impl_(std::make_unique<Impl>(config, context_graph)) {}
+    : impl_(std::make_unique<Impl>(config, std::move(context_graph))) {}
 
 OfflineStream::OfflineStream(WhisperTag tag)
     : impl_(std::make_unique<Impl>(tag)) {}
diff --git a/sherpa-onnx/csrc/offline-transducer-modified-beam-search-decoder.cc b/sherpa-onnx/csrc/offline-transducer-modified-beam-search-decoder.cc
index 317c7ad8..391620a0 100644
--- a/sherpa-onnx/csrc/offline-transducer-modified-beam-search-decoder.cc
+++ b/sherpa-onnx/csrc/offline-transducer-modified-beam-search-decoder.cc
@@ -42,7 +42,7 @@ OfflineTransducerModifiedBeamSearchDecoder::Decode(
   std::vector<ContextGraphPtr> context_graphs(batch_size, nullptr);
 
   for (int32_t i = 0; i < batch_size; ++i) {
-    const ContextState *context_state;
+    const ContextState *context_state = nullptr;
     if (ss != nullptr) {
       context_graphs[i] =
           ss[packed_encoder_out.sorted_indexes[i]]->GetContextGraph();
diff --git a/sherpa-onnx/csrc/offline-tts-character-frontend.cc b/sherpa-onnx/csrc/offline-tts-character-frontend.cc
index 2b64e67d..857200e9 100644
--- a/sherpa-onnx/csrc/offline-tts-character-frontend.cc
+++ b/sherpa-onnx/csrc/offline-tts-character-frontend.cc
@@ -30,7 +30,7 @@ static std::unordered_map<char32_t, int32_t> ReadTokens(std::istream &is) {
 
   std::string sym;
   std::u32string s;
-  int32_t id;
+  int32_t id = 0;
   while (std::getline(is, line)) {
     std::istringstream iss(line);
     iss >> sym;
@@ -138,6 +138,7 @@ OfflineTtsCharacterFrontend::ConvertTextToTokenIds(
         }
 
         ans.push_back(std::move(this_sentence));
+        this_sentence = {};
 
         // re-initialize this_sentence
         if (use_eos_bos) {
@@ -172,6 +173,7 @@ OfflineTtsCharacterFrontend::ConvertTextToTokenIds(
         }
 
         ans.push_back(std::move(this_sentence));
+        this_sentence = {};
 
         // re-initialize this_sentence
         if (use_eos_bos) {
diff --git a/sherpa-onnx/csrc/offline-tts.cc b/sherpa-onnx/csrc/offline-tts.cc
index 4349f98e..12feda0b 100644
--- a/sherpa-onnx/csrc/offline-tts.cc
+++ b/sherpa-onnx/csrc/offline-tts.cc
@@ -5,6 +5,7 @@
 #include "sherpa-onnx/csrc/offline-tts.h"
 
 #include <string>
+#include <utility>
 
 #include "sherpa-onnx/csrc/file-utils.h"
 #include "sherpa-onnx/csrc/macros.h"
@@ -87,7 +88,7 @@ OfflineTts::~OfflineTts() = default;
 GeneratedAudio OfflineTts::Generate(
     const std::string &text, int64_t sid /*=0*/, float speed /*= 1.0*/,
     GeneratedAudioCallback callback /*= nullptr*/) const {
-  return impl_->Generate(text, sid, speed, callback);
+  return impl_->Generate(text, sid, speed, std::move(callback));
 }
 
 int32_t OfflineTts::SampleRate() const { return impl_->SampleRate(); }
diff --git a/sherpa-onnx/csrc/offline-whisper-model.cc b/sherpa-onnx/csrc/offline-whisper-model.cc
index 183574f9..f73234d9 100644
--- a/sherpa-onnx/csrc/offline-whisper-model.cc
+++ b/sherpa-onnx/csrc/offline-whisper-model.cc
@@ -22,9 +22,9 @@ class OfflineWhisperModel::Impl {
   explicit Impl(const OfflineModelConfig &config)
       : config_(config),
         env_(ORT_LOGGING_LEVEL_ERROR),
+        debug_(config.debug),
         sess_opts_(GetSessionOptions(config)),
         allocator_{} {
-    debug_ = config_.debug;
     {
       auto buf = ReadFile(config.whisper.encoder);
       InitEncoder(buf.data(), buf.size());
@@ -39,9 +39,9 @@ class OfflineWhisperModel::Impl {
   explicit Impl(const SpokenLanguageIdentificationConfig &config)
       : lid_config_(config),
         env_(ORT_LOGGING_LEVEL_ERROR),
+        debug_(config_.debug),
         sess_opts_(GetSessionOptions(config)),
         allocator_{} {
-    debug_ = config_.debug;
     {
       auto buf = ReadFile(config.whisper.encoder);
       InitEncoder(buf.data(), buf.size());
@@ -148,7 +148,6 @@ class OfflineWhisperModel::Impl {
     cross_v = std::move(std::get<4>(decoder_out));
 
     const float *p_logits = std::get<0>(decoder_out).GetTensorData<float>();
-    int32_t vocab_size = VocabSize();
     const auto &all_language_ids = GetAllLanguageIDs();
 
     int32_t lang_id = all_language_ids[0];
@@ -317,18 +316,18 @@ class OfflineWhisperModel::Impl {
   std::unordered_map<int32_t, std::string> id2lang_;
 
   // model meta data
-  int32_t n_text_layer_;
-  int32_t n_text_ctx_;
-  int32_t n_text_state_;
-  int32_t n_vocab_;
-  int32_t sot_;
-  int32_t eot_;
-  int32_t blank_;
-  int32_t translate_;
-  int32_t transcribe_;
-  int32_t no_timestamps_;
-  int32_t no_speech_;
-  int32_t is_multilingual_;
+  int32_t n_text_layer_ = 0;
+  int32_t n_text_ctx_ = 0;
+  int32_t n_text_state_ = 0;
+  int32_t n_vocab_ = 0;
+  int32_t sot_ = 0;
+  int32_t eot_ = 0;
+  int32_t blank_ = 0;
+  int32_t translate_ = 0;
+  int32_t transcribe_ = 0;
+  int32_t no_timestamps_ = 0;
+  int32_t no_speech_ = 0;
+  int32_t is_multilingual_ = 0;
   std::vector<int64_t> sot_sequence_;
 };
 
diff --git a/sherpa-onnx/csrc/online-conformer-transducer-model.cc b/sherpa-onnx/csrc/online-conformer-transducer-model.cc
index 58cbce01..8e7dfa1f 100644
--- a/sherpa-onnx/csrc/online-conformer-transducer-model.cc
+++ b/sherpa-onnx/csrc/online-conformer-transducer-model.cc
@@ -4,9 +4,8 @@
 
 #include "sherpa-onnx/csrc/online-conformer-transducer-model.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <memory>
 #include <sstream>
 #include <string>
diff --git a/sherpa-onnx/csrc/online-ctc-fst-decoder.cc b/sherpa-onnx/csrc/online-ctc-fst-decoder.cc
index f5057883..95e16ba7 100644
--- a/sherpa-onnx/csrc/online-ctc-fst-decoder.cc
+++ b/sherpa-onnx/csrc/online-ctc-fst-decoder.cc
@@ -52,8 +52,9 @@ static void DecodeOne(const float *log_probs, int32_t num_rows,
     if (ok) {
       std::vector<int32_t> isymbols_out;
       std::vector<int32_t> osymbols_out;
-      ok = fst::GetLinearSymbolSequence(fst_out, &isymbols_out, &osymbols_out,
-                                        nullptr);
+      /*ok =*/fst::GetLinearSymbolSequence(fst_out, &isymbols_out,
+                                           &osymbols_out, nullptr);
+      // TODO(fangjun): handle ok is false
       std::vector<int64_t> tokens;
       tokens.reserve(isymbols_out.size());
 
diff --git a/sherpa-onnx/csrc/online-lstm-transducer-model.cc b/sherpa-onnx/csrc/online-lstm-transducer-model.cc
index 4a0e838d..eca11593 100644
--- a/sherpa-onnx/csrc/online-lstm-transducer-model.cc
+++ b/sherpa-onnx/csrc/online-lstm-transducer-model.cc
@@ -3,9 +3,8 @@
 // Copyright (c)  2023  Xiaomi Corporation
 #include "sherpa-onnx/csrc/online-lstm-transducer-model.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <memory>
 #include <sstream>
 #include <string>
diff --git a/sherpa-onnx/csrc/online-nemo-ctc-model.cc b/sherpa-onnx/csrc/online-nemo-ctc-model.cc
index 3f796e2d..e4335b4b 100644
--- a/sherpa-onnx/csrc/online-nemo-ctc-model.cc
+++ b/sherpa-onnx/csrc/online-nemo-ctc-model.cc
@@ -265,16 +265,16 @@ class OnlineNeMoCtcModel::Impl {
   std::vector<std::string> output_names_;
   std::vector<const char *> output_names_ptr_;
 
-  int32_t window_size_;
-  int32_t chunk_shift_;
-  int32_t subsampling_factor_;
-  int32_t vocab_size_;
-  int32_t cache_last_channel_dim1_;
-  int32_t cache_last_channel_dim2_;
-  int32_t cache_last_channel_dim3_;
-  int32_t cache_last_time_dim1_;
-  int32_t cache_last_time_dim2_;
-  int32_t cache_last_time_dim3_;
+  int32_t window_size_ = 0;
+  int32_t chunk_shift_ = 0;
+  int32_t subsampling_factor_ = 0;
+  int32_t vocab_size_ = 0;
+  int32_t cache_last_channel_dim1_ = 0;
+  int32_t cache_last_channel_dim2_ = 0;
+  int32_t cache_last_channel_dim3_ = 0;
+  int32_t cache_last_time_dim1_ = 0;
+  int32_t cache_last_time_dim2_ = 0;
+  int32_t cache_last_time_dim3_ = 0;
 
   Ort::Value cache_last_channel_{nullptr};
   Ort::Value cache_last_time_{nullptr};
diff --git a/sherpa-onnx/csrc/online-recognizer.cc b/sherpa-onnx/csrc/online-recognizer.cc
index a49a62f6..599a0553 100644
--- a/sherpa-onnx/csrc/online-recognizer.cc
+++ b/sherpa-onnx/csrc/online-recognizer.cc
@@ -5,9 +5,8 @@
 
 #include "sherpa-onnx/csrc/online-recognizer.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <iomanip>
 #include <memory>
 #include <sstream>
diff --git a/sherpa-onnx/csrc/online-stream.cc b/sherpa-onnx/csrc/online-stream.cc
index 0a30cf40..972133c7 100644
--- a/sherpa-onnx/csrc/online-stream.cc
+++ b/sherpa-onnx/csrc/online-stream.cc
@@ -8,6 +8,7 @@
 #include <vector>
 
 #include "sherpa-onnx/csrc/features.h"
+#include "sherpa-onnx/csrc/transducer-keyword-decoder.h"
 
 namespace sherpa_onnx {
 
@@ -15,7 +16,7 @@ class OnlineStream::Impl {
  public:
   explicit Impl(const FeatureExtractorConfig &config,
                 ContextGraphPtr context_graph)
-      : feat_extractor_(config), context_graph_(context_graph) {}
+      : feat_extractor_(config), context_graph_(std::move(context_graph)) {}
 
   void AcceptWaveform(int32_t sampling_rate, const float *waveform, int32_t n) {
     feat_extractor_.AcceptWaveform(sampling_rate, waveform, n);
@@ -146,7 +147,7 @@ class OnlineStream::Impl {
 
 OnlineStream::OnlineStream(const FeatureExtractorConfig &config /*= {}*/,
                            ContextGraphPtr context_graph /*= nullptr */)
-    : impl_(std::make_unique<Impl>(config, context_graph)) {}
+    : impl_(std::make_unique<Impl>(config, std::move(context_graph))) {}
 
 OnlineStream::~OnlineStream() = default;
 
diff --git a/sherpa-onnx/csrc/online-stream.h b/sherpa-onnx/csrc/online-stream.h
index e9958d73..1cf29de7 100644
--- a/sherpa-onnx/csrc/online-stream.h
+++ b/sherpa-onnx/csrc/online-stream.h
@@ -15,7 +15,6 @@
 #include "sherpa-onnx/csrc/online-ctc-decoder.h"
 #include "sherpa-onnx/csrc/online-paraformer-decoder.h"
 #include "sherpa-onnx/csrc/online-transducer-decoder.h"
-#include "sherpa-onnx/csrc/transducer-keyword-decoder.h"
 
 namespace sherpa_onnx {
 
diff --git a/sherpa-onnx/csrc/online-transducer-decoder.cc b/sherpa-onnx/csrc/online-transducer-decoder.cc
index 0c51eabb..682b9bc7 100644
--- a/sherpa-onnx/csrc/online-transducer-decoder.cc
+++ b/sherpa-onnx/csrc/online-transducer-decoder.cc
@@ -45,13 +45,13 @@ OnlineTransducerDecoderResult &OnlineTransducerDecoderResult::operator=(
 }
 
 OnlineTransducerDecoderResult::OnlineTransducerDecoderResult(
-    OnlineTransducerDecoderResult &&other)
+    OnlineTransducerDecoderResult &&other) noexcept
     : OnlineTransducerDecoderResult() {
   *this = std::move(other);
 }
 
 OnlineTransducerDecoderResult &OnlineTransducerDecoderResult::operator=(
-    OnlineTransducerDecoderResult &&other) {
+    OnlineTransducerDecoderResult &&other) noexcept {
   if (this == &other) {
     return *this;
   }
diff --git a/sherpa-onnx/csrc/online-transducer-decoder.h b/sherpa-onnx/csrc/online-transducer-decoder.h
index 25d798fb..e507a0fc 100644
--- a/sherpa-onnx/csrc/online-transducer-decoder.h
+++ b/sherpa-onnx/csrc/online-transducer-decoder.h
@@ -44,10 +44,10 @@ struct OnlineTransducerDecoderResult {
   OnlineTransducerDecoderResult &operator=(
       const OnlineTransducerDecoderResult &other);
 
-  OnlineTransducerDecoderResult(OnlineTransducerDecoderResult &&other);
+  OnlineTransducerDecoderResult(OnlineTransducerDecoderResult &&other) noexcept;
 
   OnlineTransducerDecoderResult &operator=(
-      OnlineTransducerDecoderResult &&other);
+      OnlineTransducerDecoderResult &&other) noexcept;
 };
 
 class OnlineStream;
diff --git a/sherpa-onnx/csrc/online-transducer-model.cc b/sherpa-onnx/csrc/online-transducer-model.cc
index 6a1fe5d5..a6cd49d9 100644
--- a/sherpa-onnx/csrc/online-transducer-model.cc
+++ b/sherpa-onnx/csrc/online-transducer-model.cc
@@ -23,7 +23,7 @@
 
 namespace {
 
-enum class ModelType {
+enum class ModelType : std::uint8_t {
   kConformer,
   kLstm,
   kZipformer,
diff --git a/sherpa-onnx/csrc/online-transducer-nemo-model.cc b/sherpa-onnx/csrc/online-transducer-nemo-model.cc
index 3869a8b2..8882c6ca 100644
--- a/sherpa-onnx/csrc/online-transducer-nemo-model.cc
+++ b/sherpa-onnx/csrc/online-transducer-nemo-model.cc
@@ -5,10 +5,9 @@
 
 #include "sherpa-onnx/csrc/online-transducer-nemo-model.h"
 
-#include <assert.h>
-#include <math.h>
-
 #include <algorithm>
+#include <cassert>
+#include <cmath>
 #include <memory>
 #include <numeric>
 #include <sstream>
@@ -429,8 +428,8 @@ class OnlineTransducerNeMoModel::Impl {
   std::vector<std::string> joiner_output_names_;
   std::vector<const char *> joiner_output_names_ptr_;
 
-  int32_t window_size_;
-  int32_t chunk_shift_;
+  int32_t window_size_ = 0;
+  int32_t chunk_shift_ = 0;
   int32_t vocab_size_ = 0;
   int32_t subsampling_factor_ = 8;
   std::string normalize_type_;
@@ -438,12 +437,12 @@ class OnlineTransducerNeMoModel::Impl {
   int32_t pred_hidden_ = -1;
 
   // encoder states
-  int32_t cache_last_channel_dim1_;
-  int32_t cache_last_channel_dim2_;
-  int32_t cache_last_channel_dim3_;
-  int32_t cache_last_time_dim1_;
-  int32_t cache_last_time_dim2_;
-  int32_t cache_last_time_dim3_;
+  int32_t cache_last_channel_dim1_ = 0;
+  int32_t cache_last_channel_dim2_ = 0;
+  int32_t cache_last_channel_dim3_ = 0;
+  int32_t cache_last_time_dim1_ = 0;
+  int32_t cache_last_time_dim2_ = 0;
+  int32_t cache_last_time_dim3_ = 0;
 
   // init encoder states
   Ort::Value cache_last_channel_{nullptr};
diff --git a/sherpa-onnx/csrc/online-wenet-ctc-model.cc b/sherpa-onnx/csrc/online-wenet-ctc-model.cc
index 34557bf1..50a7a10a 100644
--- a/sherpa-onnx/csrc/online-wenet-ctc-model.cc
+++ b/sherpa-onnx/csrc/online-wenet-ctc-model.cc
@@ -192,15 +192,15 @@ class OnlineWenetCtcModel::Impl {
   std::vector<std::string> output_names_;
   std::vector<const char *> output_names_ptr_;
 
-  int32_t head_;
-  int32_t num_blocks_;
-  int32_t output_size_;
-  int32_t cnn_module_kernel_;
-  int32_t right_context_;
-  int32_t subsampling_factor_;
-  int32_t vocab_size_;
+  int32_t head_ = 0;
+  int32_t num_blocks_ = 0;
+  int32_t output_size_ = 0;
+  int32_t cnn_module_kernel_ = 0;
+  int32_t right_context_ = 0;
+  int32_t subsampling_factor_ = 0;
+  int32_t vocab_size_ = 0;
 
-  int32_t required_cache_size_;
+  int32_t required_cache_size_ = 0;
 
   Ort::Value attn_cache_{nullptr};
   Ort::Value conv_cache_{nullptr};
diff --git a/sherpa-onnx/csrc/online-zipformer-transducer-model.cc b/sherpa-onnx/csrc/online-zipformer-transducer-model.cc
index b7e16cb6..2c9b9737 100644
--- a/sherpa-onnx/csrc/online-zipformer-transducer-model.cc
+++ b/sherpa-onnx/csrc/online-zipformer-transducer-model.cc
@@ -4,9 +4,8 @@
 
 #include "sherpa-onnx/csrc/online-zipformer-transducer-model.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <memory>
 #include <sstream>
 #include <string>
diff --git a/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc b/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc
index aff4e5cb..3dc3eedf 100644
--- a/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc
+++ b/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc
@@ -4,10 +4,8 @@
 
 #include "sherpa-onnx/csrc/online-zipformer2-ctc-model.h"
 
-#include <assert.h>
-#include <math.h>
-
 #include <algorithm>
+#include <cassert>
 #include <cmath>
 #include <numeric>
 #include <string>
@@ -90,7 +88,6 @@ class OnlineZipformer2CtcModel::Impl {
   std::vector<Ort::Value> StackStates(
       std::vector<std::vector<Ort::Value>> states) const {
     int32_t batch_size = static_cast<int32_t>(states.size());
-    int32_t num_encoders = static_cast<int32_t>(num_encoder_layers_.size());
 
     std::vector<const Ort::Value *> buf(batch_size);
 
@@ -168,7 +165,6 @@ class OnlineZipformer2CtcModel::Impl {
     assert(states.size() == m * 6 + 2);
 
     int32_t batch_size = states[0].GetTensorTypeAndShapeInfo().GetShape()[1];
-    int32_t num_encoders = num_encoder_layers_.size();
 
     std::vector<std::vector<Ort::Value>> ans;
     ans.resize(batch_size);
diff --git a/sherpa-onnx/csrc/online-zipformer2-transducer-model.cc b/sherpa-onnx/csrc/online-zipformer2-transducer-model.cc
index 5d481854..e5c44821 100644
--- a/sherpa-onnx/csrc/online-zipformer2-transducer-model.cc
+++ b/sherpa-onnx/csrc/online-zipformer2-transducer-model.cc
@@ -4,10 +4,9 @@
 
 #include "sherpa-onnx/csrc/online-zipformer2-transducer-model.h"
 
-#include <assert.h>
-#include <math.h>
-
 #include <algorithm>
+#include <cassert>
+#include <cmath>
 #include <memory>
 #include <numeric>
 #include <sstream>
diff --git a/sherpa-onnx/csrc/onnx-utils.cc b/sherpa-onnx/csrc/onnx-utils.cc
index 2d5c2082..5d9f3745 100644
--- a/sherpa-onnx/csrc/onnx-utils.cc
+++ b/sherpa-onnx/csrc/onnx-utils.cc
@@ -281,11 +281,12 @@ CopyableOrtValue &CopyableOrtValue::operator=(const CopyableOrtValue &other) {
   return *this;
 }
 
-CopyableOrtValue::CopyableOrtValue(CopyableOrtValue &&other) {
+CopyableOrtValue::CopyableOrtValue(CopyableOrtValue &&other) noexcept {
   *this = std::move(other);
 }
 
-CopyableOrtValue &CopyableOrtValue::operator=(CopyableOrtValue &&other) {
+CopyableOrtValue &CopyableOrtValue::operator=(
+    CopyableOrtValue &&other) noexcept {
   if (this == &other) {
     return *this;
   }
diff --git a/sherpa-onnx/csrc/onnx-utils.h b/sherpa-onnx/csrc/onnx-utils.h
index 0b7fcc75..b179b378 100644
--- a/sherpa-onnx/csrc/onnx-utils.h
+++ b/sherpa-onnx/csrc/onnx-utils.h
@@ -110,9 +110,9 @@ struct CopyableOrtValue {
 
   CopyableOrtValue &operator=(const CopyableOrtValue &other);
 
-  CopyableOrtValue(CopyableOrtValue &&other);
+  CopyableOrtValue(CopyableOrtValue &&other) noexcept;
 
-  CopyableOrtValue &operator=(CopyableOrtValue &&other);
+  CopyableOrtValue &operator=(CopyableOrtValue &&other) noexcept;
 };
 
 std::vector<CopyableOrtValue> Convert(std::vector<Ort::Value> values);
diff --git a/sherpa-onnx/csrc/packed-sequence.cc b/sherpa-onnx/csrc/packed-sequence.cc
index df5b9202..1c3fe91c 100644
--- a/sherpa-onnx/csrc/packed-sequence.cc
+++ b/sherpa-onnx/csrc/packed-sequence.cc
@@ -4,9 +4,8 @@
 
 #include "sherpa-onnx/csrc/packed-sequence.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <numeric>
 #include <utility>
 
@@ -57,7 +56,7 @@ PackedSequence PackPaddedSequence(OrtAllocator *allocator,
 
   int64_t max_T = p_length[indexes[0]];
 
-  int32_t sum_T = std::accumulate(p_length, p_length + n, 0);
+  auto sum_T = std::accumulate(p_length, p_length + n, static_cast<int64_t>(0));
 
   std::array<int64_t, 2> data_shape{sum_T, v_shape[2]};
 
diff --git a/sherpa-onnx/csrc/pad-sequence.cc b/sherpa-onnx/csrc/pad-sequence.cc
index d9f8ebf9..3ecf277d 100644
--- a/sherpa-onnx/csrc/pad-sequence.cc
+++ b/sherpa-onnx/csrc/pad-sequence.cc
@@ -4,9 +4,8 @@
 
 #include "sherpa-onnx/csrc/pad-sequence.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <vector>
 
 namespace sherpa_onnx {
diff --git a/sherpa-onnx/csrc/parse-options.cc b/sherpa-onnx/csrc/parse-options.cc
index f0658223..33a07f32 100644
--- a/sherpa-onnx/csrc/parse-options.cc
+++ b/sherpa-onnx/csrc/parse-options.cc
@@ -11,9 +11,8 @@
 
 #include "sherpa-onnx/csrc/parse-options.h"
 
-#include <ctype.h>
-
 #include <algorithm>
+#include <array>
 #include <cctype>
 #include <cstring>
 #include <fstream>
@@ -33,7 +32,7 @@ ParseOptions::ParseOptions(const std::string &prefix, ParseOptions *po)
   } else {
     other_parser_ = po;
   }
-  if (po != nullptr && po->prefix_ != "") {
+  if (po != nullptr && !po->prefix_.empty()) {
     prefix_ = po->prefix_ + std::string(".") + prefix;
   } else {
     prefix_ = prefix;
@@ -179,10 +178,10 @@ void ParseOptions::DisableOption(const std::string &name) {
   string_map_.erase(name);
 }
 
-int ParseOptions::NumArgs() const { return positional_args_.size(); }
+int32_t ParseOptions::NumArgs() const { return positional_args_.size(); }
 
-std::string ParseOptions::GetArg(int i) const {
-  if (i < 1 || i > static_cast<int>(positional_args_.size())) {
+std::string ParseOptions::GetArg(int32_t i) const {
+  if (i < 1 || i > static_cast<int32_t>(positional_args_.size())) {
     SHERPA_ONNX_LOGE("ParseOptions::GetArg, invalid index %d", i);
     exit(-1);
   }
@@ -191,7 +190,7 @@ std::string ParseOptions::GetArg(int i) const {
 }
 
 // We currently do not support any other options.
-enum ShellType { kBash = 0 };
+enum ShellType : std::uint8_t { kBash = 0 };
 
 // This can be changed in the code if it ever does need to be changed (as it's
 // unlikely that one compilation of this tool-set would use both shells).
@@ -213,7 +212,7 @@ static bool MustBeQuoted(const std::string &str, ShellType st) {
   if (*c == '\0') {
     return true;  // Must quote empty string
   } else {
-    const char *ok_chars[2];
+    std::array<const char *, 2> ok_chars{};
 
     // These seem not to be interpreted as long as there are no other "bad"
     // characters involved (e.g. "," would be interpreted as part of something
@@ -229,7 +228,7 @@ static bool MustBeQuoted(const std::string &str, ShellType st) {
       // are OK. All others are forbidden (this is easier since the shell
       // interprets most non-alphanumeric characters).
       if (!isalnum(*c)) {
-        const char *d;
+        const char *d = nullptr;
         for (d = ok_chars[st]; *d != '\0'; ++d) {
           if (*c == *d) break;
         }
@@ -269,22 +268,22 @@ static std::string QuoteAndEscape(const std::string &str, ShellType /*st*/) {
     escape_str = "\\\"";  // should never be accessed.
   }
 
-  char buf[2];
+  std::array<char, 2> buf{};
   buf[1] = '\0';
 
   buf[0] = quote_char;
-  std::string ans = buf;
+  std::string ans = buf.data();
   const char *c = str.c_str();
   for (; *c != '\0'; ++c) {
     if (*c == quote_char) {
       ans += escape_str;
     } else {
       buf[0] = *c;
-      ans += buf;
+      ans += buf.data();
     }
   }
   buf[0] = quote_char;
-  ans += buf;
+  ans += buf.data();
   return ans;
 }
 
@@ -293,11 +292,11 @@ std::string ParseOptions::Escape(const std::string &str) {
   return MustBeQuoted(str, kShellType) ? QuoteAndEscape(str, kShellType) : str;
 }
 
-int ParseOptions::Read(int argc, const char *const argv[]) {
+int32_t ParseOptions::Read(int32_t argc, const char *const *argv) {
   argc_ = argc;
   argv_ = argv;
   std::string key, value;
-  int i;
+  int32_t i = 0;
 
   // first pass: look for config parameter, look for priority
   for (i = 1; i < argc; ++i) {
@@ -306,13 +305,13 @@ int ParseOptions::Read(int argc, const char *const argv[]) {
         // a lone "--" marks the end of named options
         break;
       }
-      bool has_equal_sign;
+      bool has_equal_sign = false;
       SplitLongArg(argv[i], &key, &value, &has_equal_sign);
       NormalizeArgName(&key);
       Trim(&value);
-      if (key.compare("config") == 0) {
+      if (key == "config") {
         ReadConfigFile(value);
-      } else if (key.compare("help") == 0) {
+      } else if (key == "help") {
         PrintUsage();
         exit(0);
       }
@@ -330,7 +329,7 @@ int ParseOptions::Read(int argc, const char *const argv[]) {
         double_dash_seen = true;
         break;
       }
-      bool has_equal_sign;
+      bool has_equal_sign = false;
       SplitLongArg(argv[i], &key, &value, &has_equal_sign);
       NormalizeArgName(&key);
       Trim(&value);
@@ -349,14 +348,14 @@ int ParseOptions::Read(int argc, const char *const argv[]) {
     if ((std::strcmp(argv[i], "--") == 0) && !double_dash_seen) {
       double_dash_seen = true;
     } else {
-      positional_args_.push_back(std::string(argv[i]));
+      positional_args_.emplace_back(argv[i]);
     }
   }
 
   // if the user did not suppress this with --print-args = false....
   if (print_args_) {
     std::ostringstream strm;
-    for (int j = 0; j < argc; ++j) strm << Escape(argv[j]) << " ";
+    for (int32_t j = 0; j < argc; ++j) strm << Escape(argv[j]) << " ";
     strm << '\n';
     SHERPA_ONNX_LOGE("%s", strm.str().c_str());
   }
@@ -368,14 +367,14 @@ void ParseOptions::PrintUsage(bool print_command_line /*=false*/) const {
   os << '\n' << usage_ << '\n';
   // first we print application-specific options
   bool app_specific_header_printed = false;
-  for (auto it = doc_map_.begin(); it != doc_map_.end(); ++it) {
-    if (it->second.is_standard_ == false) {  // application-specific option
+  for (const auto &it : doc_map_) {
+    if (it.second.is_standard_ == false) {  // application-specific option
       if (app_specific_header_printed == false) {  // header was not yet printed
         os << "Options:" << '\n';
         app_specific_header_printed = true;
       }
-      os << "  --" << std::setw(25) << std::left << it->second.name_ << " : "
-         << it->second.use_msg_ << '\n';
+      os << "  --" << std::setw(25) << std::left << it.second.name_ << " : "
+         << it.second.use_msg_ << '\n';
     }
   }
   if (app_specific_header_printed == true) {
@@ -384,17 +383,17 @@ void ParseOptions::PrintUsage(bool print_command_line /*=false*/) const {
 
   // then the standard options
   os << "Standard options:" << '\n';
-  for (auto it = doc_map_.begin(); it != doc_map_.end(); ++it) {
-    if (it->second.is_standard_ == true) {  // we have standard option
-      os << "  --" << std::setw(25) << std::left << it->second.name_ << " : "
-         << it->second.use_msg_ << '\n';
+  for (const auto &it : doc_map_) {
+    if (it.second.is_standard_ == true) {  // we have standard option
+      os << "  --" << std::setw(25) << std::left << it.second.name_ << " : "
+         << it.second.use_msg_ << '\n';
     }
   }
   os << '\n';
   if (print_command_line) {
     std::ostringstream strm;
     strm << "Command line was: ";
-    for (int j = 0; j < argc_; ++j) strm << Escape(argv_[j]) << " ";
+    for (int32_t j = 0; j < argc_; ++j) strm << Escape(argv_[j]) << " ";
     strm << '\n';
     os << strm.str();
   }
@@ -405,9 +404,9 @@ void ParseOptions::PrintUsage(bool print_command_line /*=false*/) const {
 void ParseOptions::PrintConfig(std::ostream &os) const {
   os << '\n' << "[[ Configuration of UI-Registered options ]]" << '\n';
   std::string key;
-  for (auto it = doc_map_.begin(); it != doc_map_.end(); ++it) {
-    key = it->first;
-    os << it->second.name_ << " = ";
+  for (const auto &it : doc_map_) {
+    key = it.first;
+    os << it.second.name_ << " = ";
     if (bool_map_.end() != bool_map_.find(key)) {
       os << (*bool_map_.at(key) ? "true" : "false");
     } else if (int_map_.end() != int_map_.find(key)) {
@@ -442,13 +441,13 @@ void ParseOptions::ReadConfigFile(const std::string &filename) {
   while (std::getline(is, line)) {
     ++line_number;
     // trim out the comments
-    size_t pos;
-    if ((pos = line.find_first_of('#')) != std::string::npos) {
+    size_t pos = line.find_first_of('#');
+    if (pos != std::string::npos) {
       line.erase(pos);
     }
     // skip empty lines
     Trim(&line);
-    if (line.length() == 0) continue;
+    if (line.empty()) continue;
 
     if (line.substr(0, 2) != "--") {
       SHERPA_ONNX_LOGE(
@@ -461,7 +460,7 @@ void ParseOptions::ReadConfigFile(const std::string &filename) {
     }
 
     // parse option
-    bool has_equal_sign;
+    bool has_equal_sign = false;
     SplitLongArg(line, &key, &value, &has_equal_sign);
     NormalizeArgName(&key);
     Trim(&value);
@@ -527,7 +526,7 @@ void ParseOptions::Trim(std::string *str) const {
 bool ParseOptions::SetOption(const std::string &key, const std::string &value,
                              bool has_equal_sign) {
   if (bool_map_.end() != bool_map_.find(key)) {
-    if (has_equal_sign && value == "") {
+    if (has_equal_sign && value.empty()) {
       SHERPA_ONNX_LOGE("Invalid option --%s=", key.c_str());
       exit(-1);
     }
@@ -557,12 +556,10 @@ bool ParseOptions::ToBool(std::string str) const {
   std::transform(str.begin(), str.end(), str.begin(), ::tolower);
 
   // allow "" as a valid option for "true", so that --x is the same as --x=true
-  if ((str.compare("true") == 0) || (str.compare("t") == 0) ||
-      (str.compare("1") == 0) || (str.compare("") == 0)) {
+  if (str == "true" || str == "t" || str == "1" || str.empty()) {
     return true;
   }
-  if ((str.compare("false") == 0) || (str.compare("f") == 0) ||
-      (str.compare("0") == 0)) {
+  if (str == "false" || str == "f" || str == "0") {
     return false;
   }
   // if it is neither true nor false:
@@ -593,7 +590,7 @@ uint32_t ParseOptions::ToUint(const std::string &str) const {
 }
 
 float ParseOptions::ToFloat(const std::string &str) const {
-  float ret;
+  float ret = 0;
   if (!ConvertStringToReal(str, &ret)) {
     SHERPA_ONNX_LOGE("Invalid floating-point option \"%s\"", str.c_str());
     exit(-1);
@@ -602,7 +599,7 @@ float ParseOptions::ToFloat(const std::string &str) const {
 }
 
 double ParseOptions::ToDouble(const std::string &str) const {
-  double ret;
+  double ret = 0;
   if (!ConvertStringToReal(str, &ret)) {
     SHERPA_ONNX_LOGE("Invalid floating-point option \"%s\"", str.c_str());
     exit(-1);
diff --git a/sherpa-onnx/csrc/piper-phonemize-lexicon.cc b/sherpa-onnx/csrc/piper-phonemize-lexicon.cc
index ff5e9abe..aa7b9a2c 100644
--- a/sherpa-onnx/csrc/piper-phonemize-lexicon.cc
+++ b/sherpa-onnx/csrc/piper-phonemize-lexicon.cc
@@ -37,7 +37,7 @@ static std::unordered_map<char32_t, int32_t> ReadTokens(std::istream &is) {
 
   std::string sym;
   std::u32string s;
-  int32_t id;
+  int32_t id = 0;
   while (std::getline(is, line)) {
     std::istringstream iss(line);
     iss >> sym;
diff --git a/sherpa-onnx/csrc/resample.cc b/sherpa-onnx/csrc/resample.cc
index f82c61a9..ad5ef2a6 100644
--- a/sherpa-onnx/csrc/resample.cc
+++ b/sherpa-onnx/csrc/resample.cc
@@ -24,10 +24,9 @@
 
 #include "sherpa-onnx/csrc/resample.h"
 
-#include <assert.h>
-#include <math.h>
-#include <stdio.h>
-
+#include <cassert>
+#include <cmath>
+#include <cstdio>
 #include <cstdlib>
 #include <type_traits>
 
@@ -54,8 +53,8 @@ I Gcd(I m, I n) {
   }
   // could use compile-time assertion
   // but involves messing with complex template stuff.
-  static_assert(std::is_integral<I>::value, "");
-  while (1) {
+  static_assert(std::is_integral_v<I>);
+  while (true) {
     m %= n;
     if (m == 0) return (n > 0 ? n : -n);
     n %= m;
@@ -139,10 +138,10 @@ void LinearResample::SetIndexesAndWeights() {
     in the header as h(t) = f(t)g(t), evaluated at t.
 */
 float LinearResample::FilterFunc(float t) const {
-  float window,  // raised-cosine (Hanning) window of width
-                 // num_zeros_/2*filter_cutoff_
-      filter;    // sinc filter function
-  if (fabs(t) < num_zeros_ / (2.0 * filter_cutoff_))
+  float window = 0,  // raised-cosine (Hanning) window of width
+                     // num_zeros_/2*filter_cutoff_
+      filter = 0;    // sinc filter function
+  if (std::fabs(t) < num_zeros_ / (2.0 * filter_cutoff_))
     window = 0.5 * (1 + cos(M_2PI * filter_cutoff_ / num_zeros_ * t));
   else
     window = 0.0;  // outside support of window function
@@ -172,15 +171,15 @@ void LinearResample::Resample(const float *input, int32_t input_dim, bool flush,
   // of it we are producing here.
   for (int64_t samp_out = output_sample_offset_; samp_out < tot_output_samp;
        samp_out++) {
-    int64_t first_samp_in;
-    int32_t samp_out_wrapped;
+    int64_t first_samp_in = 0;
+    int32_t samp_out_wrapped = 0;
     GetIndexes(samp_out, &first_samp_in, &samp_out_wrapped);
     const std::vector<float> &weights = weights_[samp_out_wrapped];
     // first_input_index is the first index into "input" that we have a weight
     // for.
     int32_t first_input_index =
         static_cast<int32_t>(first_samp_in - input_sample_offset_);
-    float this_output;
+    float this_output = 0;
     if (first_input_index >= 0 &&
         first_input_index + static_cast<int32_t>(weights.size()) <= input_dim) {
       this_output =
@@ -239,7 +238,7 @@ int64_t LinearResample::GetNumOutputSamples(int64_t input_num_samp,
     // largest integer in the interval [ 0, 2 - 0.9 ) are the same (both one).
     // So when we're subtracting the window-width we can ignore the fractional
     // part.
-    int32_t window_width_ticks = floor(window_width * tick_freq);
+    int32_t window_width_ticks = std::floor(window_width * tick_freq);
     // The time-period of the output that we can sample gets reduced
     // by the window-width (which is actually the distance from the
     // center to the edge of the windowing function) if we're not
@@ -287,7 +286,7 @@ void LinearResample::SetRemainder(const float *input, int32_t input_dim) {
   // that are "in the past" relative to the beginning of the latest
   // input... anyway, storing more remainder than needed is not harmful.
   int32_t max_remainder_needed =
-      ceil(samp_rate_in_ * num_zeros_ / filter_cutoff_);
+      std::ceil(samp_rate_in_ * num_zeros_ / filter_cutoff_);
   input_remainder_.resize(max_remainder_needed);
   for (int32_t index = -static_cast<int32_t>(input_remainder_.size());
        index < 0; index++) {
diff --git a/sherpa-onnx/csrc/resample.h b/sherpa-onnx/csrc/resample.h
index 2006ae90..d6e22a19 100644
--- a/sherpa-onnx/csrc/resample.h
+++ b/sherpa-onnx/csrc/resample.h
@@ -130,11 +130,11 @@ class LinearResample {
   // the following variables keep track of where we are in a particular signal,
   // if it is being provided over multiple calls to Resample().
 
-  int64_t input_sample_offset_;   ///< The number of input samples we have
-                                  ///< already received for this signal
-                                  ///< (including anything in remainder_)
-  int64_t output_sample_offset_;  ///< The number of samples we have already
-                                  ///< output for this signal.
+  int64_t input_sample_offset_ = 0;   ///< The number of input samples we have
+                                      ///< already received for this signal
+                                      ///< (including anything in remainder_)
+  int64_t output_sample_offset_ = 0;  ///< The number of samples we have already
+                                      ///< output for this signal.
   std::vector<float> input_remainder_;  ///< A small trailing part of the
                                         ///< previously seen input signal.
 };
diff --git a/sherpa-onnx/csrc/session.cc b/sherpa-onnx/csrc/session.cc
index 431a6a76..0f6ed89d 100644
--- a/sherpa-onnx/csrc/session.cc
+++ b/sherpa-onnx/csrc/session.cc
@@ -21,14 +21,14 @@
 
 namespace sherpa_onnx {
 
-
 static void OrtStatusFailure(OrtStatus *status, const char *s) {
-    const auto &api = Ort::GetApi();
-    const char *msg = api.GetErrorMessage(status);
-    SHERPA_ONNX_LOGE(
+  const auto &api = Ort::GetApi();
+  const char *msg = api.GetErrorMessage(status);
+  SHERPA_ONNX_LOGE(
       "Failed to enable TensorRT : %s."
-      "Available providers: %s. Fallback to cuda", msg, s);
-    api.ReleaseStatus(status);
+      "Available providers: %s. Fallback to cuda",
+      msg, s);
+  api.ReleaseStatus(status);
 }
 
 static Ort::SessionOptions GetSessionOptionsImpl(int32_t num_threads,
@@ -65,29 +65,28 @@ static Ort::SessionOptions GetSessionOptionsImpl(int32_t num_threads,
     }
     case Provider::kTRT: {
       struct TrtPairs {
-        const char* op_keys;
-        const char* op_values;
+        const char *op_keys;
+        const char *op_values;
       };
 
       std::vector<TrtPairs> trt_options = {
-        {"device_id", "0"},
-        {"trt_max_workspace_size", "2147483648"},
-        {"trt_max_partition_iterations", "10"},
-        {"trt_min_subgraph_size", "5"},
-        {"trt_fp16_enable", "0"},
-        {"trt_detailed_build_log", "0"},
-        {"trt_engine_cache_enable", "1"},
-        {"trt_engine_cache_path", "."},
-        {"trt_timing_cache_enable", "1"},
-        {"trt_timing_cache_path", "."}
-      };
+          {"device_id", "0"},
+          {"trt_max_workspace_size", "2147483648"},
+          {"trt_max_partition_iterations", "10"},
+          {"trt_min_subgraph_size", "5"},
+          {"trt_fp16_enable", "0"},
+          {"trt_detailed_build_log", "0"},
+          {"trt_engine_cache_enable", "1"},
+          {"trt_engine_cache_path", "."},
+          {"trt_timing_cache_enable", "1"},
+          {"trt_timing_cache_path", "."}};
       // ToDo : Trt configs
       // "trt_int8_enable"
       // "trt_int8_use_native_calibration_table"
       // "trt_dump_subgraphs"
 
-      std::vector<const char*> option_keys, option_values;
-      for (const TrtPairs& pair : trt_options) {
+      std::vector<const char *> option_keys, option_values;
+      for (const TrtPairs &pair : trt_options) {
         option_keys.emplace_back(pair.op_keys);
         option_values.emplace_back(pair.op_values);
       }
@@ -95,19 +94,23 @@ static Ort::SessionOptions GetSessionOptionsImpl(int32_t num_threads,
       std::vector<std::string> available_providers =
           Ort::GetAvailableProviders();
       if (std::find(available_providers.begin(), available_providers.end(),
-                "TensorrtExecutionProvider") != available_providers.end()) {
-        const auto& api = Ort::GetApi();
+                    "TensorrtExecutionProvider") != available_providers.end()) {
+        const auto &api = Ort::GetApi();
 
-        OrtTensorRTProviderOptionsV2* tensorrt_options;
-        OrtStatus *statusC = api.CreateTensorRTProviderOptions(
-                                    &tensorrt_options);
+        OrtTensorRTProviderOptionsV2 *tensorrt_options = nullptr;
+        OrtStatus *statusC =
+            api.CreateTensorRTProviderOptions(&tensorrt_options);
         OrtStatus *statusU = api.UpdateTensorRTProviderOptions(
-                tensorrt_options, option_keys.data(), option_values.data(),
-                option_keys.size());
+            tensorrt_options, option_keys.data(), option_values.data(),
+            option_keys.size());
         sess_opts.AppendExecutionProvider_TensorRT_V2(*tensorrt_options);
 
-        if (statusC) { OrtStatusFailure(statusC, os.str().c_str()); }
-        if (statusU) { OrtStatusFailure(statusU, os.str().c_str()); }
+        if (statusC) {
+          OrtStatusFailure(statusC, os.str().c_str());
+        }
+        if (statusU) {
+          OrtStatusFailure(statusU, os.str().c_str());
+        }
 
         api.ReleaseTensorRTProviderOptions(tensorrt_options);
       }
diff --git a/sherpa-onnx/csrc/silero-vad-model.cc b/sherpa-onnx/csrc/silero-vad-model.cc
index a0c1e6c5..3c8233ea 100644
--- a/sherpa-onnx/csrc/silero-vad-model.cc
+++ b/sherpa-onnx/csrc/silero-vad-model.cc
@@ -20,11 +20,11 @@ class SileroVadModel::Impl {
       : config_(config),
         env_(ORT_LOGGING_LEVEL_ERROR),
         sess_opts_(GetSessionOptions(config)),
-        allocator_{} {
+        allocator_{},
+        sample_rate_(config.sample_rate) {
     auto buf = ReadFile(config.silero_vad.model);
     Init(buf.data(), buf.size());
 
-    sample_rate_ = config.sample_rate;
     if (sample_rate_ != 16000) {
       SHERPA_ONNX_LOGE("Expected sample rate 16000. Given: %d",
                        config.sample_rate);
diff --git a/sherpa-onnx/csrc/slice.cc b/sherpa-onnx/csrc/slice.cc
index 6cc57758..5b7cf97d 100644
--- a/sherpa-onnx/csrc/slice.cc
+++ b/sherpa-onnx/csrc/slice.cc
@@ -4,9 +4,8 @@
 
 #include "sherpa-onnx/csrc/slice.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <vector>
 
 namespace sherpa_onnx {
diff --git a/sherpa-onnx/csrc/speaker-embedding-extractor-impl.cc b/sherpa-onnx/csrc/speaker-embedding-extractor-impl.cc
index 53ff9940..fac2ea65 100644
--- a/sherpa-onnx/csrc/speaker-embedding-extractor-impl.cc
+++ b/sherpa-onnx/csrc/speaker-embedding-extractor-impl.cc
@@ -12,7 +12,7 @@ namespace sherpa_onnx {
 
 namespace {
 
-enum class ModelType {
+enum class ModelType : std::uint8_t {
   kWeSpeaker,
   k3dSpeaker,
   kNeMo,
diff --git a/sherpa-onnx/csrc/speaker-embedding-manager.cc b/sherpa-onnx/csrc/speaker-embedding-manager.cc
index 569b8d4f..6c90c195 100644
--- a/sherpa-onnx/csrc/speaker-embedding-manager.cc
+++ b/sherpa-onnx/csrc/speaker-embedding-manager.cc
@@ -122,7 +122,7 @@ class SpeakerEmbeddingManager::Impl {
 
     Eigen::VectorXf scores = embedding_matrix_ * v;
 
-    Eigen::VectorXf::Index max_index;
+    Eigen::VectorXf::Index max_index = 0;
     float max_score = scores.maxCoeff(&max_index);
     if (max_score < threshold) {
       return {};
@@ -178,11 +178,12 @@ class SpeakerEmbeddingManager::Impl {
 
   std::vector<std::string> GetAllSpeakers() const {
     std::vector<std::string> all_speakers;
+    all_speakers.reserve(name2row_.size());
     for (const auto &p : name2row_) {
       all_speakers.push_back(p.first);
     }
 
-    std::stable_sort(all_speakers.begin(), all_speakers.end());
+    std::sort(all_speakers.begin(), all_speakers.end());
     return all_speakers;
   }
 
diff --git a/sherpa-onnx/csrc/spoken-language-identification-impl.cc b/sherpa-onnx/csrc/spoken-language-identification-impl.cc
index 016ac7e0..b8984a66 100644
--- a/sherpa-onnx/csrc/spoken-language-identification-impl.cc
+++ b/sherpa-onnx/csrc/spoken-language-identification-impl.cc
@@ -18,7 +18,7 @@ namespace sherpa_onnx {
 
 namespace {
 
-enum class ModelType {
+enum class ModelType : std::uint8_t {
   kWhisper,
   kUnknown,
 };
diff --git a/sherpa-onnx/csrc/stack.cc b/sherpa-onnx/csrc/stack.cc
index 302ec733..1d0fac51 100644
--- a/sherpa-onnx/csrc/stack.cc
+++ b/sherpa-onnx/csrc/stack.cc
@@ -71,8 +71,8 @@ Ort::Value Stack(OrtAllocator *allocator,
   T *dst = ans.GetTensorMutableData<T>();
 
   for (int32_t i = 0; i != leading_size; ++i) {
-    for (int32_t n = 0; n != static_cast<int32_t>(values.size()); ++n) {
-      const T *src = values[n]->GetTensorData<T>();
+    for (auto value : values) {
+      const T *src = value->GetTensorData<T>();
       src += i * trailing_size;
 
       std::copy(src, src + trailing_size, dst);
diff --git a/sherpa-onnx/csrc/symbol-table.cc b/sherpa-onnx/csrc/symbol-table.cc
index 524b2689..8862972b 100644
--- a/sherpa-onnx/csrc/symbol-table.cc
+++ b/sherpa-onnx/csrc/symbol-table.cc
@@ -36,7 +36,7 @@ SymbolTable::SymbolTable(AAssetManager *mgr, const std::string &filename) {
 
 void SymbolTable::Init(std::istream &is) {
   std::string sym;
-  int32_t id;
+  int32_t id = 0;
   while (is >> sym >> id) {
 #if 0
     // we disable the test here since for some multi-lingual BPE models
diff --git a/sherpa-onnx/csrc/text-utils.cc b/sherpa-onnx/csrc/text-utils.cc
index 04586dd8..3f12e146 100644
--- a/sherpa-onnx/csrc/text-utils.cc
+++ b/sherpa-onnx/csrc/text-utils.cc
@@ -5,9 +5,8 @@
 
 #include "sherpa-onnx/csrc/text-utils.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <cctype>
 #include <cstdint>
 #include <limits>
diff --git a/sherpa-onnx/csrc/transducer-keyword-decoder.cc b/sherpa-onnx/csrc/transducer-keyword-decoder.cc
index af78cb9c..b94b7ba1 100644
--- a/sherpa-onnx/csrc/transducer-keyword-decoder.cc
+++ b/sherpa-onnx/csrc/transducer-keyword-decoder.cc
@@ -151,7 +151,6 @@ void TransducerKeywordDecoder::Decode(
 
       if (matched) {
         float ys_prob = 0.0;
-        int32_t length = best_hyp.ys_probs.size();
         for (int32_t i = 0; i < matched_state->level; ++i) {
           ys_prob += best_hyp.ys_probs[i];
         }
diff --git a/sherpa-onnx/csrc/transpose.cc b/sherpa-onnx/csrc/transpose.cc
index 5ec32667..90a34599 100644
--- a/sherpa-onnx/csrc/transpose.cc
+++ b/sherpa-onnx/csrc/transpose.cc
@@ -4,9 +4,8 @@
 
 #include "sherpa-onnx/csrc/transpose.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <vector>
 
 namespace sherpa_onnx {
diff --git a/sherpa-onnx/csrc/unbind.cc b/sherpa-onnx/csrc/unbind.cc
index ffe5a6c3..587e268c 100644
--- a/sherpa-onnx/csrc/unbind.cc
+++ b/sherpa-onnx/csrc/unbind.cc
@@ -4,9 +4,8 @@
 
 #include "sherpa-onnx/csrc/unbind.h"
 
-#include <assert.h>
-
 #include <algorithm>
+#include <cassert>
 #include <functional>
 #include <numeric>
 #include <utility>
diff --git a/sherpa-onnx/csrc/utils.cc b/sherpa-onnx/csrc/utils.cc
index 93de43e7..b5df9682 100644
--- a/sherpa-onnx/csrc/utils.cc
+++ b/sherpa-onnx/csrc/utils.cc
@@ -30,7 +30,6 @@ static bool EncodeBase(const std::vector<std::string> &lines,
   std::vector<float> tmp_thresholds;
   std::vector<std::string> tmp_phrases;
 
-  std::string line;
   std::string word;
   bool has_scores = false;
   bool has_thresholds = false;
@@ -72,6 +71,7 @@ static bool EncodeBase(const std::vector<std::string> &lines,
       }
     }
     ids->push_back(std::move(tmp_ids));
+    tmp_ids = {};
     tmp_scores.push_back(score);
     tmp_phrases.push_back(phrase);
     tmp_thresholds.push_back(threshold);
diff --git a/sherpa-onnx/csrc/wave-reader.cc b/sherpa-onnx/csrc/wave-reader.cc
index b9d26279..1058db59 100644
--- a/sherpa-onnx/csrc/wave-reader.cc
+++ b/sherpa-onnx/csrc/wave-reader.cc
@@ -100,13 +100,13 @@ struct WaveHeader {
   int32_t subchunk2_id;    // a tag of this chunk
   int32_t subchunk2_size;  // size of subchunk2
 };
-static_assert(sizeof(WaveHeader) == 44, "");
+static_assert(sizeof(WaveHeader) == 44);
 
 // Read a wave file of mono-channel.
 // Return its samples normalized to the range [-1, 1).
 std::vector<float> ReadWaveImpl(std::istream &is, int32_t *sampling_rate,
                                 bool *is_ok) {
-  WaveHeader header;
+  WaveHeader header{};
   is.read(reinterpret_cast<char *>(&header), sizeof(header));
   if (!is) {
     *is_ok = false;
diff --git a/sherpa-onnx/csrc/wave-writer.cc b/sherpa-onnx/csrc/wave-writer.cc
index f20af4b1..069b6276 100644
--- a/sherpa-onnx/csrc/wave-writer.cc
+++ b/sherpa-onnx/csrc/wave-writer.cc
@@ -37,7 +37,7 @@ struct WaveHeader {
 
 bool WriteWave(const std::string &filename, int32_t sampling_rate,
                const float *samples, int32_t n) {
-  WaveHeader header;
+  WaveHeader header{};
   header.chunk_id = 0x46464952;      // FFIR
   header.format = 0x45564157;        // EVAW
   header.subchunk1_id = 0x20746d66;  // "fmt "