diff --git a/sherpa-onnx/csrc/jieba-lexicon.cc b/sherpa-onnx/csrc/jieba-lexicon.cc
index 82b45cdfe..e62324103 100644
--- a/sherpa-onnx/csrc/jieba-lexicon.cc
+++ b/sherpa-onnx/csrc/jieba-lexicon.cc
@@ -102,13 +102,13 @@ class JiebaLexicon::Impl {
       this_sentence.push_back(blank);
 
       if (w == "。" || w == "！" || w == "？" || w == "，") {
-        ans.push_back(std::move(this_sentence));
+        ans.emplace_back(std::move(this_sentence));
         this_sentence = {};
       }
     }  // for (const auto &w : words)
 
     if (!this_sentence.empty()) {
-      ans.push_back(std::move(this_sentence));
+      ans.emplace_back(std::move(this_sentence));
     }
 
     return ans;
diff --git a/sherpa-onnx/csrc/lexicon.cc b/sherpa-onnx/csrc/lexicon.cc
index c635f7ffd..24184f180 100644
--- a/sherpa-onnx/csrc/lexicon.cc
+++ b/sherpa-onnx/csrc/lexicon.cc
@@ -253,7 +253,7 @@ std::vector<TokenIDs> Lexicon::ConvertTextToTokenIdsChinese(
         if (eos != -1) {
           this_sentence.push_back(eos);
         }
-        ans.push_back(std::move(this_sentence));
+        ans.emplace_back(std::move(this_sentence));
         this_sentence = {};
 
         if (sil != -1) {
@@ -283,7 +283,7 @@ std::vector<TokenIDs> Lexicon::ConvertTextToTokenIdsChinese(
   if (eos != -1) {
     this_sentence.push_back(eos);
   }
-  ans.push_back(std::move(this_sentence));
+  ans.emplace_back(std::move(this_sentence));
 
   return ans;
 }
@@ -324,7 +324,7 @@ std::vector<TokenIDs> Lexicon::ConvertTextToTokenIdsNotChinese(
 
       if (w != ",") {
         this_sentence.push_back(blank);
-        ans.push_back(std::move(this_sentence));
+        ans.emplace_back(std::move(this_sentence));
         this_sentence = {};
       }
 
@@ -348,7 +348,7 @@ std::vector<TokenIDs> Lexicon::ConvertTextToTokenIdsNotChinese(
   }
 
   if (!this_sentence.empty()) {
-    ans.push_back(std::move(this_sentence));
+    ans.emplace_back(std::move(this_sentence));
   }
 
   return ans;
diff --git a/sherpa-onnx/csrc/melo-tts-lexicon.cc b/sherpa-onnx/csrc/melo-tts-lexicon.cc
index b213c4516..561aaa276 100644
--- a/sherpa-onnx/csrc/melo-tts-lexicon.cc
+++ b/sherpa-onnx/csrc/melo-tts-lexicon.cc
@@ -91,7 +91,6 @@ class MeloTtsLexicon::Impl {
     std::vector<TokenIDs> ans;
     TokenIDs this_sentence;
 
-    int32_t blank = token2id_.at("_");
     for (const auto &w : words) {
       auto ids = ConvertWordToIds(w);
       if (ids.tokens.empty()) {
diff --git a/sherpa-onnx/csrc/offline-tts-character-frontend.cc b/sherpa-onnx/csrc/offline-tts-character-frontend.cc
index c92240581..72481e094 100644
--- a/sherpa-onnx/csrc/offline-tts-character-frontend.cc
+++ b/sherpa-onnx/csrc/offline-tts-character-frontend.cc
@@ -136,7 +136,7 @@ std::vector<TokenIDs> OfflineTtsCharacterFrontend::ConvertTextToTokenIds(
           this_sentence.push_back(eos_id);
         }
 
-        ans.push_back(std::move(this_sentence));
+        ans.emplace_back(std::move(this_sentence));
         this_sentence = {};
 
         // re-initialize this_sentence
@@ -152,7 +152,7 @@ std::vector<TokenIDs> OfflineTtsCharacterFrontend::ConvertTextToTokenIds(
     }
 
     if (static_cast<int32_t>(this_sentence.size()) > 1 + use_eos_bos) {
-      ans.push_back(std::move(this_sentence));
+      ans.emplace_back(std::move(this_sentence));
     }
   } else {
     // not adding blank
@@ -171,7 +171,7 @@ std::vector<TokenIDs> OfflineTtsCharacterFrontend::ConvertTextToTokenIds(
           this_sentence.push_back(eos_id);
         }
 
-        ans.push_back(std::move(this_sentence));
+        ans.emplace_back(std::move(this_sentence));
         this_sentence = {};
 
         // re-initialize this_sentence
@@ -182,7 +182,7 @@ std::vector<TokenIDs> OfflineTtsCharacterFrontend::ConvertTextToTokenIds(
     }
 
     if (this_sentence.size() > 1) {
-      ans.push_back(std::move(this_sentence));
+      ans.emplace_back(std::move(this_sentence));
     }
   }
 
diff --git a/sherpa-onnx/csrc/offline-tts-frontend.h b/sherpa-onnx/csrc/offline-tts-frontend.h
index 6ea4c5dfa..0216284f1 100644
--- a/sherpa-onnx/csrc/offline-tts-frontend.h
+++ b/sherpa-onnx/csrc/offline-tts-frontend.h
@@ -15,12 +15,12 @@ namespace sherpa_onnx {
 struct TokenIDs {
   TokenIDs() = default;
 
-  /*implicit*/ TokenIDs(const std::vector<int64_t> &tokens)  // NOLINT
-      : tokens{tokens} {}
+  /*implicit*/ TokenIDs(std::vector<int64_t> tokens)  // NOLINT
+      : tokens{std::move(tokens)} {}
 
-  TokenIDs(const std::vector<int64_t> &tokens,
-           const std::vector<int64_t> &tones)
-      : tokens{tokens}, tones{tones} {}
+  TokenIDs(std::vector<int64_t> tokens,  // NOLINT
+           std::vector<int64_t> tones)   // NOLINT
+      : tokens{std::move(tokens)}, tones{std::move(tones)} {}
 
   std::string ToString() const;
 
diff --git a/sherpa-onnx/csrc/onnx-utils.cc b/sherpa-onnx/csrc/onnx-utils.cc
index 1a6bf704b..0f637020a 100644
--- a/sherpa-onnx/csrc/onnx-utils.cc
+++ b/sherpa-onnx/csrc/onnx-utils.cc
@@ -157,8 +157,8 @@ Ort::Value View(Ort::Value *v) {
 
 float ComputeSum(const Ort::Value *v, int32_t n /*= -1*/) {
   std::vector<int64_t> shape = v->GetTensorTypeAndShapeInfo().GetShape();
-  auto size = static_cast<int32_t>(std::accumulate(
-      shape.begin(), shape.end(), 1, std::multiplies<int64_t>()));
+  auto size = static_cast<int32_t>(
+      std::accumulate(shape.begin(), shape.end(), 1, std::multiplies<>()));
   if (n != -1 && n < size && n > 0) {
     size = n;
   }
@@ -170,8 +170,8 @@ float ComputeSum(const Ort::Value *v, int32_t n /*= -1*/) {
 
 float ComputeMean(const Ort::Value *v, int32_t n /*= -1*/) {
   std::vector<int64_t> shape = v->GetTensorTypeAndShapeInfo().GetShape();
-  auto size = static_cast<int32_t>(std::accumulate(
-      shape.begin(), shape.end(), 1, std::multiplies<int64_t>()));
+  auto size = static_cast<int32_t>(
+      std::accumulate(shape.begin(), shape.end(), 1, std::multiplies<>()));
 
   if (n != -1 && n < size && n > 0) {
     size = n;
diff --git a/sherpa-onnx/csrc/piper-phonemize-lexicon.cc b/sherpa-onnx/csrc/piper-phonemize-lexicon.cc
index 8ba101cc3..c5f315eae 100644
--- a/sherpa-onnx/csrc/piper-phonemize-lexicon.cc
+++ b/sherpa-onnx/csrc/piper-phonemize-lexicon.cc
@@ -239,12 +239,12 @@ std::vector<TokenIDs> PiperPhonemizeLexicon::ConvertTextToTokenIds(
   if (meta_data_.is_piper || meta_data_.is_icefall) {
     for (const auto &p : phonemes) {
       phoneme_ids = PiperPhonemesToIds(token2id_, p);
-      ans.push_back(std::move(phoneme_ids));
+      ans.emplace_back(std::move(phoneme_ids));
     }
   } else if (meta_data_.is_coqui) {
     for (const auto &p : phonemes) {
       phoneme_ids = CoquiPhonemesToIds(token2id_, p, meta_data_);
-      ans.push_back(std::move(phoneme_ids));
+      ans.emplace_back(std::move(phoneme_ids));
     }
 
   } else {