refactor: replace std::function with function pointer + context pointer

lib/fizzy/capi.cpp

@@ -101,19 +101,19 @@ inline fizzy::ExecutionResult unwrap(const FizzyExecutionResult& result) noexcep
         return unwrap(result.value);
 }
 
-inline auto unwrap(FizzyExternalFn func, void* context) noexcept
+fizzy::ExecutionResult unwrapped_external_function(
+    void* context, fizzy::Instance& instance, const fizzy::Value* args, int depth)
 {
-    return [func, context](fizzy::Instance& instance, const fizzy::Value* args,
-               int depth) noexcept -> fizzy::ExecutionResult {
-        const auto result = func(context, wrap(&instance), wrap(args), depth);
-        return unwrap(result);
-    };
+    const auto* c_external_function = static_cast<const FizzyExternalFunction*>(context);
+    return unwrap(c_external_function->function(
+        c_external_function->context, wrap(&instance), wrap(args), depth));
 }
 
+
 inline fizzy::ExternalFunction unwrap(const FizzyExternalFunction& external_func)
 {
-    return fizzy::ExternalFunction{
-        unwrap(external_func.function, external_func.context), unwrap(external_func.type)};
+    return fizzy::ExternalFunction{unwrapped_external_function,
+        const_cast<FizzyExternalFunction*>(&external_func), unwrap(external_func.type)};
 }
 
 inline fizzy::ImportedFunction unwrap(const FizzyImportedFunction& c_imported_func)
@@ -131,8 +131,8 @@ inline fizzy::ImportedFunction unwrap(const FizzyImportedFunction& c_imported_fu
                                std::nullopt :
                                std::make_optional(unwrap(c_type.output));
 
-    imported_func.function = unwrap(
-        c_imported_func.external_function.function, c_imported_func.external_function.context);
+    imported_func.function = unwrapped_external_function;
+    imported_func.context = const_cast<FizzyExternalFunction*>(&c_imported_func.external_function);
 
     return imported_func;
 }

lib/fizzy/execute.cpp

@@ -526,7 +526,8 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, const Value* args,
 
     assert(instance.module->imported_function_types.size() == instance.imported_functions.size());
     if (func_idx < instance.imported_functions.size())
-        return instance.imported_functions[func_idx].function(instance, args, depth);
+        return instance.imported_functions[func_idx].function(
+            instance.imported_functions[func_idx].context, instance, args, depth);
 
     const auto& code = instance.module->get_code(func_idx);
     auto* const memory = instance.memory.get();
@@ -642,7 +643,12 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, const Value* args,
             if (expected_type != actual_type)
                 goto trap;
 
-            if (!invoke_function(actual_type, called_func->function, instance, stack, depth))
+            // TODO simplify to get rid of lambda
+            const auto func = [&called_func](Instance&, const Value* called_args, int _depth) {
+                return execute(*called_func->instance, called_func->func_idx, called_args, _depth);
+            };
+
+            if (!invoke_function(actual_type, func, instance, stack, depth))
                 goto trap;
             break;
         }

lib/fizzy/instantiate.cpp

@@ -330,11 +330,8 @@ std::unique_ptr<Instance> instantiate(std::unique_ptr<const Module> module,
         auto it_table = instance->table->begin() + elementsec_offsets[i];
         for (const auto idx : instance->module->elementsec[i].init)
         {
-            auto func = [idx, &instance_ref = *instance](fizzy::Instance&, const Value* args,
-                            int depth) { return execute(instance_ref, idx, args, depth); };
-
             *it_table++ =
-                ExternalFunction{std::move(func), instance->module->get_function_type(idx)};
+                TableFunction{instance.get(), idx, instance->module->get_function_type(idx), {}};
         }
     }
 
@@ -360,11 +357,7 @@ std::unique_ptr<Instance> instantiate(std::unique_ptr<const Module> module,
                     auto it_table = shared_instance->table->begin() + elementsec_offsets[i];
                     for ([[maybe_unused]] auto _ : shared_instance->module->elementsec[i].init)
                     {
-                        // Wrap the function with the lambda capturing shared instance
-                        auto& table_function = (*it_table)->function;
-                        table_function = [shared_instance, func = std::move(table_function)](
-                                             fizzy::Instance& _instance, const Value* args,
-                                             int depth) { return func(_instance, args, depth); };
+                        (*it_table)->shared_instance = shared_instance;
                         ++it_table;
                     }
                 }
@@ -417,7 +410,7 @@ std::vector<ExternalFunction> resolve_imported_functions(
         }
 
         external_functions.emplace_back(
-            ExternalFunction{std::move(it->function), module_func_type});
+            ExternalFunction{it->function, it->context, module_func_type});
     }
 
     return external_functions;
@@ -428,18 +421,23 @@ std::optional<FuncIdx> find_exported_function(const Module& module, std::string_
     return find_export(module, ExternalKind::Function, name);
 }
 
-std::optional<ExternalFunction> find_exported_function(Instance& instance, std::string_view name)
+std::optional<ExportedFunction> find_exported_function(Instance& instance, std::string_view name)
 {
     const auto opt_index = find_export(*instance.module, ExternalKind::Function, name);
     if (!opt_index.has_value())
         return std::nullopt;
 
     const auto idx = *opt_index;
-    auto func = [idx, &instance](fizzy::Instance&, const Value* args, int depth) {
-        return execute(instance, idx, args, depth);
+    auto func = [](void* context, fizzy::Instance&, const Value* args, int depth) {
+        auto* instance_and_idx = static_cast<std::pair<Instance*, FuncIdx>*>(context);
+        return execute(*instance_and_idx->first, instance_and_idx->second, args, depth);
     };
 
-    return ExternalFunction{std::move(func), instance.module->get_function_type(idx)};
+    ExportedFunction exported_func;
+    exported_func.context.reset(new std::pair<Instance*, FuncIdx>(&instance, idx));
+    exported_func.external_function = {
+        std::move(func), exported_func.context.get(), instance.module->get_function_type(idx)};
+    return exported_func;
 }
 
 std::optional<ExternalGlobal> find_exported_global(Instance& instance, std::string_view name)

lib/fizzy/instantiate.hpp

@@ -22,13 +22,24 @@ namespace fizzy
 struct ExecutionResult;
 struct Instance;
 
+using ExternalFunctionPtr = ExecutionResult (*)(void* context, Instance&, const Value*, int depth);
+
 struct ExternalFunction
 {
-    std::function<ExecutionResult(Instance&, const Value*, int depth)> function;
+    ExternalFunctionPtr function;
+    void* context;
+    FuncType type;
+};
+
+struct TableFunction
+{
+    Instance* instance;
+    FuncIdx func_idx;
     FuncType type;
+    std::shared_ptr<Instance> shared_instance;
 };
 
-using table_elements = std::vector<std::optional<ExternalFunction>>;
+using table_elements = std::vector<std::optional<TableFunction>>;
 using table_ptr = std::unique_ptr<table_elements, void (*)(table_elements*)>;
 
 struct ExternalTable
@@ -101,7 +112,8 @@ struct ImportedFunction
     std::string name;
     std::vector<ValType> inputs;
     std::optional<ValType> output;
-    std::function<ExecutionResult(Instance&, const Value*, int depth)> function;
+    ExternalFunctionPtr function;
+    void* context;
 };
 
 // Create vector of ExternalFunctions ready to be passed to instantiate.
@@ -113,8 +125,14 @@ std::vector<ExternalFunction> resolve_imported_functions(
 // Find exported function index by name.
 std::optional<FuncIdx> find_exported_function(const Module& module, std::string_view name);
 
+struct ExportedFunction
+{
+    std::unique_ptr<std::pair<Instance*, FuncIdx>> context;
+    ExternalFunction external_function;
+};
+
 // Find exported function by name.
-std::optional<ExternalFunction> find_exported_function(Instance& instance, std::string_view name);
+std::optional<ExportedFunction> find_exported_function(Instance& instance, std::string_view name);
 
 // Find exported global by name.
 std::optional<ExternalGlobal> find_exported_global(Instance& instance, std::string_view name);

test/spectests/spectests.cpp

@@ -77,7 +77,7 @@ struct test_results
 
 struct imports
 {
-    std::vector<fizzy::ExternalFunction> functions;
+    std::vector<fizzy::ExportedFunction> functions;
     std::vector<fizzy::ExternalTable> tables;
     std::vector<fizzy::ExternalMemory> memories;
     std::vector<fizzy::ExternalGlobal> globals;
@@ -128,8 +128,17 @@ class test_runner
                         continue;
                     }
 
+
+                    std::vector<fizzy::ExternalFunction> external_functions(
+                        imports.functions.size());
+                    std::transform(imports.functions.begin(), imports.functions.end(),
+                        external_functions.begin(),
+                        [](const auto& imported_func) { return imported_func.external_function; });
+
+                    m_instances_external_functions[name] = std::move(imports.functions);
+
                     m_instances[name] =
-                        fizzy::instantiate(std::move(module), std::move(imports.functions),
+                        fizzy::instantiate(std::move(module), std::move(external_functions),
                             std::move(imports.tables), std::move(imports.memories),
                             std::move(imports.globals), TestMemoryPagesLimit);
 
@@ -139,20 +148,23 @@ class test_runner
                 {
                     fail(std::string{"Parsing failed with error: "} + ex.what());
                     m_instances.erase(name);
+                    m_instances_external_functions.erase(name);
                     m_last_module_name.clear();
                     continue;
                 }
                 catch (const fizzy::validation_error& ex)
                 {
                     fail(std::string{"Validation failed with error: "} + ex.what());
                     m_instances.erase(name);
+                    m_instances_external_functions.erase(name);
                     m_last_module_name.clear();
                     continue;
                 }
                 catch (const fizzy::instantiate_error& ex)
                 {
                     fail(std::string{"Instantiation failed with error: "} + ex.what());
                     m_instances.erase(name);
+                    m_instances_external_functions.erase(name);
                     m_last_module_name.clear();
                     continue;
                 }
@@ -338,7 +350,13 @@ class test_runner
                         continue;
                     }
 
-                    fizzy::instantiate(std::move(module), std::move(imports.functions),
+                    std::vector<fizzy::ExternalFunction> external_functions(
+                        imports.functions.size());
+                    std::transform(imports.functions.begin(), imports.functions.end(),
+                        external_functions.begin(),
+                        [](const auto& imported_func) { return imported_func.external_function; });
+
+                    fizzy::instantiate(std::move(module), std::move(external_functions),
                         std::move(imports.tables), std::move(imports.memories),
                         std::move(imports.globals));
                 }
@@ -564,32 +582,41 @@ class test_runner
         {
             const auto it_registered = m_registered_names.find(import.module);
             if (it_registered == m_registered_names.end())
-                return {{}, "Module \"" + import.module + "\" not registered."};
+            {
+                imports empty_imports;
+                return {
+                    std::move(empty_imports), "Module \"" + import.module + "\" not registered."};
+            }
 
             const auto module_name = it_registered->second;
             const auto it_instance = m_instances.find(module_name);
             if (it_instance == m_instances.end())
-                return {{}, "Module not instantiated."};
+            {
+                imports empty_imports;
+                return {std::move(empty_imports), "Module not instantiated."};
+            }
 
             auto& instance = it_instance->second;
 
             if (import.kind == fizzy::ExternalKind::Function)
             {
-                const auto func = fizzy::find_exported_function(*instance, import.name);
+                auto func = fizzy::find_exported_function(*instance, import.name);
                 if (!func.has_value())
                 {
-                    return {{},
+                    imports empty_imports;
+                    return {std::move(empty_imports),
                         "Function \"" + import.name + "\" not found in \"" + import.module + "\"."};
                 }
 
-                result.functions.emplace_back(*func);
+                result.functions.emplace_back(std::move(*func));
             }
             else if (import.kind == fizzy::ExternalKind::Table)
             {
                 const auto table = fizzy::find_exported_table(*instance, import.name);
                 if (!table.has_value())
                 {
-                    return {{},
+                    imports empty_imports;
+                    return {std::move(empty_imports),
                         "Table \"" + import.name + "\" not found in \"" + import.module + "\"."};
                 }
 
@@ -600,7 +627,8 @@ class test_runner
                 const auto memory = fizzy::find_exported_memory(*instance, import.name);
                 if (!memory.has_value())
                 {
-                    return {{},
+                    imports empty_imports;
+                    return {std::move(empty_imports),
                         "Memory \"" + import.name + "\" not found in \"" + import.module + "\"."};
                 }
 
@@ -611,15 +639,16 @@ class test_runner
                 const auto global = fizzy::find_exported_global(*instance, import.name);
                 if (!global.has_value())
                 {
-                    return {{},
+                    imports empty_imports;
+                    return {std::move(empty_imports),
                         "Global \"" + import.name + "\" not found in \"" + import.module + "\"."};
                 }
 
                 result.globals.emplace_back(*global);
             }
         }
 
-        return {result, ""};
+        return {std::move(result), ""};
     }
 
     void pass()
@@ -661,6 +690,8 @@ class test_runner
 
     test_settings m_settings;
     std::unordered_map<std::string, std::unique_ptr<fizzy::Instance>> m_instances;
+    std::unordered_map<std::string, std::vector<fizzy::ExportedFunction>>
+        m_instances_external_functions;
     std::unordered_map<std::string, std::string> m_registered_names;
     std::string m_last_module_name;
     test_results m_results;