Merge pull request #527 from wasmx/parser_no_default_case

Introduce UNREACHABLE macro

lib/fizzy/CMakeLists.txt

@@ -10,6 +10,8 @@ target_include_directories(fizzy PUBLIC ${FIZZY_INCLUDE_DIR})
 target_sources(
     fizzy PRIVATE
     ${FIZZY_INCLUDE_DIR}/fizzy/fizzy.h
+    asserts.cpp
+    asserts.hpp
     cxx20/bit.hpp
     cxx20/span.hpp
     bytes.hpp
@@ -37,6 +39,10 @@ target_sources(
     value.hpp
 )
 
+if(CMAKE_BUILD_TYPE STREQUAL Coverage AND CMAKE_CXX_COMPILER_ID MATCHES GNU)
+    set_source_files_properties(asserts.cpp PROPERTIES COMPILE_DEFINITIONS GCOV)
+endif()
+
 # The fizzy::fizzy-internal links fizzy::fizzy library with access to internal headers.
 add_library(fizzy-internal INTERFACE)
 add_library(fizzy::fizzy-internal ALIAS fizzy-internal)

lib/fizzy/asserts.cpp

@@ -0,0 +1,20 @@
+// Fizzy: A fast WebAssembly interpreter
+// Copyright 2020 The Fizzy Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "asserts.hpp"
+
+#ifdef GCOV
+extern "C" void __gcov_flush();
+#endif
+
+namespace fizzy
+{
+bool unreachable() noexcept
+{
+#ifdef GCOV
+    __gcov_flush();
+#endif
+    return false;  // LCOV_EXCL_LINE
+}
+}  // namespace fizzy

lib/fizzy/asserts.hpp

@@ -0,0 +1,28 @@
+// Fizzy: A fast WebAssembly interpreter
+// Copyright 2020 The Fizzy Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#include <cassert>
+
+#ifndef __has_builtin
+#define __has_builtin(name) 0
+#endif
+
+#ifndef __has_feature
+#define __has_feature(name) 0
+#endif
+
+
+namespace fizzy
+{
+/// A helper for assert(unreachable()). Always returns false. Also flushes coverage data.
+bool unreachable() noexcept;
+}  // namespace fizzy
+
+#ifndef NDEBUG
+#define FIZZY_UNREACHABLE() assert(fizzy::unreachable())
+#elif __has_builtin(__builtin_unreachable)
+#define FIZZY_UNREACHABLE() __builtin_unreachable()
+#else
+#define FIZZY_UNREACHABLE() (void)0
+#endif

lib/fizzy/execute.cpp

@@ -3,6 +3,7 @@
 // SPDX-License-Identifier: Apache-2.0
 
 #include "execute.hpp"
+#include "asserts.hpp"
 #include "cxx20/bit.hpp"
 #include "stack.hpp"
 #include "trunc_boundaries.hpp"
@@ -1554,8 +1555,7 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, const Value* args,
         }
 
         default:
-            assert(false);
-            break;
+            FIZZY_UNREACHABLE();
         }
     }
 

lib/fizzy/parser.cpp

@@ -3,6 +3,7 @@
 // SPDX-License-Identifier: Apache-2.0
 
 #include "parser.hpp"
+#include "asserts.hpp"
 #include "leb128.hpp"
 #include "limits.hpp"
 #include "types.hpp"
@@ -532,8 +533,8 @@ std::unique_ptr<const Module> parse(bytes_view input)
         case ExternalKind::Global:
             module->imported_global_types.emplace_back(import.desc.global);
             break;
-        default:
-            assert(false);
+        default:                  // LCOV_EXCL_LINE
+            FIZZY_UNREACHABLE();  // LCOV_EXCL_LINE
         }
     }
 
@@ -635,8 +636,8 @@ std::unique_ptr<const Module> parse(bytes_view input)
             if (export_.index >= total_global_count)
                 throw validation_error{"invalid index of an exported global"};
             break;
-        default:
-            assert(false);
+        default:                  // LCOV_EXCL_LINE
+            FIZZY_UNREACHABLE();  // LCOV_EXCL_LINE
         }
         if (!export_names.emplace(export_.name).second)
             throw validation_error{"duplicate export name " + export_.name};

test/unittests/CMakeLists.txt

@@ -10,13 +10,15 @@ target_link_libraries(fizzy-unittests PRIVATE fizzy::fizzy-internal fizzy::test-
 target_sources(
     fizzy-unittests PRIVATE
     api_test.cpp
+    asserts_test.cpp
     capi_test.cpp
     constexpr_vector_test.cpp
     cxx20_bit_test.cpp
     cxx20_span_test.cpp
     end_to_end_test.cpp
     execute_call_test.cpp
     execute_control_test.cpp
+    execute_death_test.cpp
     execute_floating_point_test.cpp
     execute_numeric_test.cpp
     execute_test.cpp

test/unittests/asserts_test.cpp

@@ -0,0 +1,14 @@
+// Fizzy: A fast WebAssembly interpreter
+// Copyright 2020 The Fizzy Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "asserts.hpp"
+#include <gtest/gtest.h>
+
+#if !defined(NDEBUG) || __has_feature(undefined_behavior_sanitizer)
+TEST(asserts_death, unreachable)
+{
+    static constexpr auto unreachable = []() noexcept { FIZZY_UNREACHABLE(); };
+    EXPECT_DEATH(unreachable(), "unreachable");
+}
+#endif

test/unittests/execute_death_test.cpp

@@ -0,0 +1,28 @@
+// Fizzy: A fast WebAssembly interpreter
+// Copyright 2020 The Fizzy Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "asserts.hpp"
+#include "execute.hpp"
+#include <gtest/gtest.h>
+
+using namespace fizzy;
+
+#if !defined(NDEBUG) || __has_feature(undefined_behavior_sanitizer)
+TEST(execute_death, malformed_instruction_opcode)
+{
+    constexpr auto malformed_opcode = static_cast<Instr>(6);
+
+    Code code;
+    code.instructions.emplace_back(malformed_opcode);
+    code.instructions.emplace_back(Instr::end);
+
+    auto module = std::make_unique<Module>();
+    module->typesec.emplace_back(FuncType{});
+    module->funcsec.emplace_back(TypeIdx{0});
+    module->codesec.emplace_back(std::move(code));
+
+    auto instance = instantiate(std::move(module));
+    EXPECT_DEATH(execute(*instance, 0, nullptr), "unreachable");
+}
+#endif