diff --git a/CMakeLists.txt b/CMakeLists.txt
index c52a92da..49fd925b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -153,7 +153,6 @@ endforeach(flag)
 # Debug flags
 set(DEBUG_CXX_FLAGS
   -O0 -g3 -ggdb3 -fno-limit-debug-info
-  -ftrapv
 )
 foreach(flag ${DEBUG_CXX_FLAGS})
   check_cxx_compiler_flag(${flag} has_flag_${flag})
@@ -162,6 +161,11 @@ foreach(flag ${DEBUG_CXX_FLAGS})
   endif(has_flag_${flag})
 endforeach(flag)
 
+# Seems buggy on Clang: see https://bugs.llvm.org/show_bug.cgi?id=16404
+if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -ftrapv")
+endif()
+
 # Release flags
 set(RELEASE_CXX_FLAGS
   -O3 -DNDEBUG
diff --git a/src/fec_base.h b/src/fec_base.h
index 6eec5cf2..e5cc810f 100644
--- a/src/fec_base.h
+++ b/src/fec_base.h
@@ -772,7 +772,7 @@ void FecCode<T>::decode_prepare(
     vec::Vector<T>* words)
 {
     const vec::Vector<T>& fragments_ids = context.get_fragments_id();
-    for (int i = 0; i < this->n_data; ++i) {
+    for (unsigned i = 0; i < this->n_data; ++i) {
         const int j = fragments_ids.get(i);
         auto data = props[j].get(ValueLocation(offset, j));
 
@@ -814,7 +814,7 @@ void FecCode<T>::decode_apply(
 
     // compute N(x) and stored in vec1_n
     vec1_n.zero_fill();
-    for (int i = 0; i <= k - 1; ++i) {
+    for (unsigned i = 0; i <= k - 1; ++i) {
         vec1_n.set(
             fragments_ids.get(i),
             this->gf->mul(words->get(i), inv_A_i.get(fragments_ids.get(i))));
@@ -927,11 +927,6 @@ bool FecCode<T>::decode_packet(
 
     decode_build();
 
-    int n_words = code_len;
-    if (type == FecType::SYSTEMATIC) {
-        n_words = n_data;
-    }
-
     // vector of buffers storing data read from chunk
     vec::Buffers<uint8_t> words_char(n_data, buf_size);
     std::vector<uint8_t*>* words_mem_char = words_char.get_mem();
@@ -1109,10 +1104,12 @@ void FecCode<T>::decode_apply(
 
     unsigned k = this->n_data; // number of fragments received
 
+    assert(k != 0);
+
     // compute N'(x) = sum_i{n_i * x^z_i}
     // where n_i=v_i/A'_i(x_i)
     buf1_n.zero_fill();
-    for (int i = 0; i <= k - 1; ++i) {
+    for (unsigned i = 0; i <= k - 1; ++i) {
         this->gf->mul_coef_to_buf(
             inv_A_i.get(fragments_ids.get(i)),
             words->get(i),
diff --git a/src/fec_context.h b/src/fec_context.h
index 4fedda59..5d151dff 100644
--- a/src/fec_context.h
+++ b/src/fec_context.h
@@ -160,6 +160,9 @@ class DecodeContext {
             return *vec1_2k;
         case CtxVec::V2K2:
             return *vec2_2k;
+        // To quell an overzealous `Wreturn-type` from GCC.
+        default:
+            throw InvalidArgument("invalid Vec type");
         }
     }
 
@@ -170,6 +173,9 @@ class DecodeContext {
             return *A;
         case CtxPoly::S:
             return *S;
+        // To quell an overzealous `Wreturn-type` from GCC.
+        default:
+            throw InvalidArgument("invalid Poly type");
         }
     }
 
@@ -186,6 +192,9 @@ class DecodeContext {
             return *buf2_2k;
         case CtxBuf::B2KMK:
             return *buf1_len2k_minus_k;
+        // To quell an overzealous `Wreturn-type` from GCC.
+        default:
+            throw InvalidArgument("invalid Buf type");
         }
     }
 
@@ -222,7 +231,7 @@ class DecodeContext {
             A->set(0, 1);
         }
 
-        for (int i = 0; i < k; ++i) {
+        for (unsigned i = 0; i < k; ++i) {
             A->mul_to_x_plus_coef(this->gf->sub(0, vx.get(i)));
         }
 
@@ -239,7 +248,7 @@ class DecodeContext {
 
         // compute 1/(x_i * A_i(x_i))
         // we care only about elements corresponding to fragments_ids
-        for (unsigned i = 0; i < k; ++i) {
+        for (int i = 0; i < static_cast<int>(k); ++i) {
             unsigned j = fragments_ids->get(i);
             if (i != vx_zero) {
                 inv_A_i->set(
diff --git a/src/fec_rs_fnt.h b/src/fec_rs_fnt.h
index 6f6f767a..9a52eef6 100644
--- a/src/fec_rs_fnt.h
+++ b/src/fec_rs_fnt.h
@@ -120,8 +120,9 @@ class RsFnt : public FecCode<T> {
         // vector stores r^{i} for i = 0, ... , n-1
         this->r_powers = std::unique_ptr<vec::Vector<T>>(
             new vec::Vector<T>(*(this->gf), this->n));
-        for (int i = 0; i < this->n; i++)
+        for (unsigned i = 0; i < this->n; i++) {
             this->r_powers->set(i, this->gf->exp(this->r, i));
+        }
     }
 
     int get_n_outputs() override
diff --git a/src/fec_rs_gf2n_fft.h b/src/fec_rs_gf2n_fft.h
index 5f47cc16..8c7c7a94 100644
--- a/src/fec_rs_gf2n_fft.h
+++ b/src/fec_rs_gf2n_fft.h
@@ -97,8 +97,9 @@ class RsGf2nFft : public FecCode<T> {
         // vector stores r^{i} for i = 0, ... , k
         this->r_powers = std::unique_ptr<vec::Vector<T>>(
             new vec::Vector<T>(*(this->gf), this->n));
-        for (int i = 0; i < this->n; i++)
+        for (unsigned i = 0; i < this->n; i++) {
             this->r_powers->set(i, this->gf->exp(this->r, i));
+        }
     }
 
     int get_n_outputs() override
diff --git a/src/fec_rs_gf2n_fft_add.h b/src/fec_rs_gf2n_fft_add.h
index 96a7a9f2..6d257dd6 100644
--- a/src/fec_rs_gf2n_fft_add.h
+++ b/src/fec_rs_gf2n_fft_add.h
@@ -144,7 +144,7 @@ class RsGf2nFftAdd : public FecCode<T> {
         vec::Vector<T> vx(*(this->gf), k);
 
         int vx_zero = -1;
-        for (int i = 0; i < this->n_data; ++i) {
+        for (unsigned i = 0; i < this->n_data; ++i) {
             T val = betas->get(fragments_ids.get(i));
             vx.set(i, val);
             if (val == 0) {
@@ -191,7 +191,7 @@ class RsGf2nFftAdd : public FecCode<T> {
 
         // FIXME: split this step in decode_init as multiplicative FFT
         vec::Vector<T> vx(*(this->gf), k);
-        for (int i = 0; i < this->n_data; ++i) {
+        for (unsigned i = 0; i < this->n_data; ++i) {
             vx.set(i, this->betas->get(fragments_ids.get(i)));
         }
 
diff --git a/src/fec_rs_gfp_fft.h b/src/fec_rs_gfp_fft.h
index e3b2207f..828e2ccc 100644
--- a/src/fec_rs_gfp_fft.h
+++ b/src/fec_rs_gfp_fft.h
@@ -152,8 +152,9 @@ class RsGfpFft : public FecCode<T> {
         // vector stores r^{i} for i = 0, ... , k
         this->r_powers = std::unique_ptr<vec::Vector<T>>(
             new vec::Vector<T>(*(this->gf), this->n));
-        for (int i = 0; i < this->n; i++)
+        for (unsigned i = 0; i < this->n; i++) {
             this->r_powers->set(i, this->gf->exp(this->r, i));
+        }
     }
 
     int get_n_outputs() override
diff --git a/src/fec_rs_nf4.h b/src/fec_rs_nf4.h
index 3afb742b..a296cc78 100644
--- a/src/fec_rs_nf4.h
+++ b/src/fec_rs_nf4.h
@@ -107,8 +107,9 @@ class RsNf4 : public FecCode<T> {
         // vector stores r^{i} for i = 0, ... , k
         this->r_powers = std::unique_ptr<vec::Vector<T>>(
             new vec::Vector<T>(*ngff4, this->n));
-        for (int i = 0; i < this->n; i++)
+        for (unsigned i = 0; i < this->n; i++) {
             this->r_powers->set(i, ngff4->exp(this->r, i));
+        }
     }
 
     int get_n_outputs() override
diff --git a/src/gf_ring.h b/src/gf_ring.h
index 731661b9..cae89d70 100644
--- a/src/gf_ring.h
+++ b/src/gf_ring.h
@@ -888,7 +888,7 @@ template <typename T>
 void RingModN<T>::neg(size_t n, T* x) const
 {
     // add y to the first half of `x`
-    for (int i = 0; i < n; i++) {
+    for (size_t i = 0; i < n; i++) {
         x[i] = sub(0, x[i]);
     }
 }
diff --git a/src/simd_256_u32.h b/src/simd_256_u32.h
index a888e2c8..383aca05 100644
--- a/src/simd_256_u32.h
+++ b/src/simd_256_u32.h
@@ -320,7 +320,7 @@ inline aint128 m256i_to_uint128(m256i v)
 {
     aint128 hi, lo;
     _mm256_storeu2_m128i((m128i*)&hi, (m128i*)&lo, v);
-    return lo;
+    return lo; // NOLINT(clang-analyzer-core.uninitialized.UndefReturn)
 }
 
 inline __uint128_t add(__uint128_t a, __uint128_t b)