diff --git a/include/cmcpp/context.hpp b/include/cmcpp/context.hpp
index 5eb1e4d..6b5f7c7 100644
--- a/include/cmcpp/context.hpp
+++ b/include/cmcpp/context.hpp
@@ -109,14 +109,14 @@ namespace cmcpp
     public:
         CanonicalOptions opts;
         ComponentInstance inst;
-        func_t<R, Args...> ft;
+        func_t<R(Args...)> ft;
         std::optional<Task> supertask;
         std::optional<std::function<void()>> on_return;
         std::function<std::future<void>(std::future<void>)> on_block;
         int num_borrows = 0;
         ContextLocalStorage context();
 
-        Task(CanonicalOptions &opts, ComponentInstance &inst, func_t<R, Args...> &ft, std::optional<Task> &supertask = std::nullopt, std::optional<std::function<void()>> &on_return = std::nullopt, std::function<std::future<void>(std::future<void>)> &on_block = std::nullopt)
+        Task(CanonicalOptions &opts, ComponentInstance &inst, func_t<R(Args...)> &ft, std::optional<Task> &supertask = std::nullopt, std::optional<std::function<void()>> &on_return = std::nullopt, std::function<std::future<void>(std::future<void>)> &on_block = std::nullopt)
             : opts(opts), inst(inst), ft(ft), supertask(supertask), on_return(on_return), on_block(on_block) {}
     };
 
diff --git a/include/cmcpp/lift.hpp b/include/cmcpp/lift.hpp
index bf89780..4316159 100644
--- a/include/cmcpp/lift.hpp
+++ b/include/cmcpp/lift.hpp
@@ -53,7 +53,7 @@ namespace cmcpp
     }
 
     template <Field T>
-    inline T lift_flat_values(const LiftLowerContext &cx, uint max_flat, const CoreValueIter &vi)
+    inline T lift_flat_values(const LiftLowerContext &cx, uint32_t max_flat, const CoreValueIter &vi)
     {
         auto flat_types = ValTrait<T>::flat_types;
         if (flat_types.size() > max_flat)
diff --git a/include/cmcpp/lower.hpp b/include/cmcpp/lower.hpp
index 563bfff..c4dbca8 100644
--- a/include/cmcpp/lower.hpp
+++ b/include/cmcpp/lower.hpp
@@ -76,7 +76,7 @@ namespace cmcpp
     }
 
     template <Field... Ts>
-    inline WasmValVector lower_flat_values(LiftLowerContext &cx, uint max_flat, uint32_t *out_param, Ts &&...vs)
+    inline WasmValVector lower_flat_values(LiftLowerContext &cx, uint32_t max_flat, uint32_t *out_param, Ts &&...vs)
     {
         WasmValVector retVal = {};
         // cx.inst.may_leave=false;
diff --git a/include/cmcpp/traits.hpp b/include/cmcpp/traits.hpp
index 85e0909..3448ef8 100644
--- a/include/cmcpp/traits.hpp
+++ b/include/cmcpp/traits.hpp
@@ -23,6 +23,14 @@ namespace cmcpp
     using bytes = uint32_t;
     using size = uint32_t;
 
+    static constexpr int ceil_log2(std::size_t n) {
+        return (n <= 1) ? 0 : 1 + ceil_log2((n + 1) / 2);
+    }
+
+    static constexpr int ceil_div8(int bits) {
+        return (bits + 7) / 8;
+    }
+
     enum class WasmValType : uint8_t
     {
         UNKNOWN,
@@ -666,7 +674,7 @@ namespace cmcpp
         static constexpr ValType type = ValType::Variant;
         using inner_type = typename std::variant<Ts...>;
 
-        static constexpr int match = static_cast<int>(std::ceil(std::log2(std::variant_size_v<inner_type>) / 8.0));
+        static constexpr int match = ceil_div8(ceil_log2(std::variant_size_v<inner_type>));
         using discriminant_type = std::conditional_t<match == 0, uint8_t, std::conditional_t<match == 1, uint8_t, std::conditional_t<match == 2, uint16_t, std::conditional_t<match == 3, uint32_t, void>>>>;
         static constexpr uint32_t max_case_alignment = []() constexpr
         {
@@ -696,18 +704,26 @@ namespace cmcpp
             ((i = std::max(i, ValTrait<Ts>::flat_types.size())), ...);
             return i + 1;
         }();
+        template<size_t StartIndex, typename First, typename... Rest>
+        static constexpr void process_types(std::array<WasmValType, flat_types_len>& flat)
+        {
+            for (auto& ft : ValTrait<First>::flat_types) {
+                if (StartIndex < flat_types_len) {
+                    flat[StartIndex] = join(flat[StartIndex], ft);
+                    process_types<StartIndex + 1, Rest...>(flat);
+                }
+            }
+        }
+        template<size_t StartIndex>
+        static constexpr void process_types(std::array<WasmValType, flat_types_len>& flat)
+        {
+        }
         static constexpr std::array<WasmValType, flat_types_len> flat_types = []() constexpr
         {
             std::array<WasmValType, flat_types_len> flat;
             flat.fill(WasmValType::i32);
             flat[0] = ValTrait<discriminant_type>::flat_types[0];
-            ([&]()
-             {
-                size_t i = 1;
-                for (auto &ft : ValTrait<Ts>::flat_types) {
-                    flat[i] = join(flat[i], ft);
-                    ++i;
-                } }(), ...);
+            process_types<1, Ts...>(flat);
             return flat;
         }();
     };
@@ -739,8 +755,8 @@ namespace cmcpp
     using enum_t = uint32_t;
 
     //  Func  --------------------------------------------------------------------
-    constexpr uint MAX_FLAT_PARAMS = 16;
-    constexpr uint MAX_FLAT_RESULTS = 1;
+    constexpr uint32_t MAX_FLAT_PARAMS = 16;
+    constexpr uint32_t MAX_FLAT_RESULTS = 1;
 
     template <typename>
     struct func_t_impl;
diff --git a/include/wamr.hpp b/include/wamr.hpp
index 952e8ee..211bc51 100644
--- a/include/wamr.hpp
+++ b/include/wamr.hpp
@@ -1,15 +1,18 @@
+#ifndef CMCPP_WAMR_HPP
+#define CMCPP_WAMR_HPP
+
 #include "wasm_export.h"
 #include "cmcpp.hpp"
 
 namespace cmcpp
 {
 
-    void trap(const char *msg)
+    inline void trap(const char *msg)
     {
         throw new std::runtime_error(msg);
     }
 
-    std::vector<wasm_val_t> wasmVal2wam_val_t(const WasmValVector &values)
+    inline std::vector<wasm_val_t> wasmVal2wam_val_t(const WasmValVector &values)
     {
         std::vector<wasm_val_t> result;
         result.reserve(values.size());
@@ -41,7 +44,7 @@ namespace cmcpp
         return result;
     }
 
-    WasmValVector wam_val_t2wasmVal(size_t count, const wasm_val_t *values)
+    inline WasmValVector wam_val_t2wasmVal(size_t count, const wasm_val_t *values)
     {
         WasmValVector result;
         result.reserve(count);
@@ -94,7 +97,7 @@ namespace cmcpp
             std::vector<wasm_val_t> inputs = wasmVal2wam_val_t(lowered_args);
 
             constexpr size_t output_size = std::is_same<result_t, void>::value ? 0 : 1;
-            wasm_val_t outputs[output_size];
+            wasm_val_t outputs[output_size == 0 ? 1 : output_size];
 
             bool success = wasm_runtime_call_wasm_a(exec_env, guest_func,
                                                     output_size, outputs,
@@ -121,7 +124,7 @@ namespace cmcpp
         };
     }
 
-    std::pair<void *, size_t> convert(void *dest, uint32_t dest_byte_len, const void *src, uint32_t src_byte_len, Encoding from_encoding, Encoding to_encoding)
+    inline std::pair<void *, size_t> convert(void *dest, uint32_t dest_byte_len, const void *src, uint32_t src_byte_len, Encoding from_encoding, Encoding to_encoding)
     {
         if (from_encoding == to_encoding)
         {
@@ -236,9 +239,11 @@ namespace cmcpp
         return symbol;
     }
 
-    bool host_module(const char *module_name, NativeSymbol *native_symbols, uint32_t n_native_symbols)
+    inline bool host_module(const char *module_name, NativeSymbol *native_symbols, uint32_t n_native_symbols)
     {
         return wasm_runtime_register_natives_raw(module_name, native_symbols, n_native_symbols);
     }
 
 }
+
+#endif
\ No newline at end of file