Prevent undefined behavior from c_api_func_imports == NULL (#1883)

The module instance's c_api_func_imports may be NULL under some circumstances,
add checks before accessing it.

core/iwasm/aot/aot_runtime.c

@@ -1787,7 +1787,9 @@ aot_invoke_native(WASMExecEnv *exec_env, uint32 func_idx, uint32 argc,
     AOTModuleInstanceExtra *module_inst_extra =
         (AOTModuleInstanceExtra *)module_inst->e;
     CApiFuncImport *c_api_func_import =
-        module_inst_extra->c_api_func_imports + func_idx;
+        module_inst_extra->c_api_func_imports
+            ? module_inst_extra->c_api_func_imports + func_idx
+            : NULL;
     uint32 *func_type_indexes = module_inst->func_type_indexes;
     uint32 func_type_idx = func_type_indexes[func_idx];
     AOTFuncType *func_type = aot_module->func_types[func_type_idx];
@@ -1803,7 +1805,8 @@ aot_invoke_native(WASMExecEnv *exec_env, uint32 func_idx, uint32 argc,
 
     import_func = aot_module->import_funcs + func_idx;
     if (import_func->call_conv_wasm_c_api)
-        func_ptr = c_api_func_import->func_ptr_linked;
+        func_ptr =
+            c_api_func_import ? c_api_func_import->func_ptr_linked : NULL;
 
     if (!func_ptr) {
         snprintf(buf, sizeof(buf),

core/iwasm/interpreter/wasm_interp_classic.c

@@ -891,7 +891,7 @@ wasm_interp_call_func_native(WASMModuleInstance *module_inst,
     if (!func_import->call_conv_wasm_c_api) {
         native_func_pointer = module_inst->import_func_ptrs[cur_func_index];
     }
-    else {
+    else if (module_inst->e->c_api_func_imports) {
         c_api_func_import = module_inst->e->c_api_func_imports + cur_func_index;
         native_func_pointer = c_api_func_import->func_ptr_linked;
     }

core/iwasm/interpreter/wasm_interp_fast.c

@@ -925,7 +925,7 @@ wasm_interp_call_func_native(WASMModuleInstance *module_inst,
     if (!func_import->call_conv_wasm_c_api) {
         native_func_pointer = module_inst->import_func_ptrs[cur_func_index];
     }
-    else {
+    else if (module_inst->e->c_api_func_imports) {
         c_api_func_import = module_inst->e->c_api_func_imports + cur_func_index;
         native_func_pointer = c_api_func_import->func_ptr_linked;
     }

core/iwasm/interpreter/wasm_runtime.c

@@ -2908,8 +2908,14 @@ llvm_jit_invoke_native(WASMExecEnv *exec_env, uint32 func_idx, uint32 argc,
 
     import_func = &module->import_functions[func_idx].u.function;
     if (import_func->call_conv_wasm_c_api) {
-        c_api_func_import = module_inst->e->c_api_func_imports + func_idx;
-        func_ptr = c_api_func_import->func_ptr_linked;
+        if (module_inst->e->c_api_func_imports) {
+            c_api_func_import = module_inst->e->c_api_func_imports + func_idx;
+            func_ptr = c_api_func_import->func_ptr_linked;
+        }
+        else {
+            c_api_func_import = NULL;
+            func_ptr = NULL;
+        }
     }
 
     if (!func_ptr) {