[lldb/Lua] Implement a Simple Lua Script Interpreter Prototype

This implements a very elementary Lua script interpreter. It supports
running a single command as well as running interactively. It uses
editline if available. It's still missing a bunch of stuff though. Some
things that I intentionally ingored for now are that I/O isn't properly
hooked up (so every print goes to stdout) and the non-editline support
which is not handling a bunch of corner cases. The latter is a matter of
reusing existing code in the Python interpreter.

Discussion on the mailing list:
http://lists.llvm.org/pipermail/lldb-dev/2019-December/015812.html

Differential revision: https://reviews.llvm.org/D71234

lldb/cmake/modules/LLDBConfig.cmake

@@ -113,6 +113,9 @@ if ((NOT MSVC) OR MSVC12)
   add_definitions( -DHAVE_ROUND )
 endif()
 
+if (LLDB_ENABLE_LUA)
+  find_package(Lua REQUIRED)
+endif()
 
 if (LLDB_ENABLE_LIBEDIT)
   find_package(LibEdit REQUIRED)

lldb/include/lldb/Core/IOHandler.h

@@ -52,6 +52,7 @@ class IOHandler {
     REPL,
     ProcessIO,
     PythonInterpreter,
+    LuaInterpreter,
     PythonCode,
     Other
   };

lldb/source/Plugins/ScriptInterpreter/Lua/CMakeLists.txt

@@ -1,7 +1,11 @@
 add_lldb_library(lldbPluginScriptInterpreterLua PLUGIN
+  Lua.cpp
   ScriptInterpreterLua.cpp
 
   LINK_LIBS
     lldbCore
     lldbInterpreter
-  )
+  )
+
+target_include_directories(lldbPluginScriptInterpreterLua PUBLIC ${LUA_INCLUDE_DIR})
+target_link_libraries(lldbPluginScriptInterpreterLua INTERFACE ${LUA_LIBRARIES})

lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp

@@ -0,0 +1,27 @@
+//===-- Lua.cpp -----------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "Lua.h"
+#include "llvm/Support/FormatVariadic.h"
+
+using namespace lldb_private;
+
+llvm::Error Lua::Run(llvm::StringRef buffer) {
+  int error =
+      luaL_loadbuffer(m_lua_state, buffer.data(), buffer.size(), "buffer") ||
+      lua_pcall(m_lua_state, 0, 0, 0);
+  if (!error)
+    return llvm::Error::success();
+
+  llvm::Error e = llvm::make_error<llvm::StringError>(
+      llvm::formatv("{0}\n", lua_tostring(m_lua_state, -1)),
+      llvm::inconvertibleErrorCode());
+  // Pop error message from the stack.
+  lua_pop(m_lua_state, 1);
+  return e;
+}

lldb/source/Plugins/ScriptInterpreter/Lua/Lua.h

@@ -0,0 +1,39 @@
+//===-- ScriptInterpreterLua.h ----------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef liblldb_Lua_h_
+#define liblldb_Lua_h_
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Error.h"
+
+#include "lua.hpp"
+
+namespace lldb_private {
+
+class Lua {
+public:
+  Lua() : m_lua_state(luaL_newstate()) {
+    assert(m_lua_state);
+    luaL_openlibs(m_lua_state);
+  }
+
+  ~Lua() {
+    assert(m_lua_state);
+    luaL_openlibs(m_lua_state);
+  }
+
+  llvm::Error Run(llvm::StringRef buffer);
+
+private:
+  lua_State *m_lua_state;
+};
+
+} // namespace lldb_private
+
+#endif // liblldb_Lua_h_

lldb/source/Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.cpp

@@ -7,35 +7,73 @@
 //===----------------------------------------------------------------------===//
 
 #include "ScriptInterpreterLua.h"
+#include "Lua.h"
 #include "lldb/Core/Debugger.h"
 #include "lldb/Core/PluginManager.h"
 #include "lldb/Core/StreamFile.h"
+#include "lldb/Interpreter/CommandReturnObject.h"
 #include "lldb/Utility/Stream.h"
 #include "lldb/Utility/StringList.h"
-
-#include "llvm/Support/Threading.h"
-
-#include <mutex>
+#include "lldb/Utility/Timer.h"
 
 using namespace lldb;
 using namespace lldb_private;
 
+class IOHandlerLuaInterpreter : public IOHandlerDelegate,
+                                public IOHandlerEditline {
+public:
+  IOHandlerLuaInterpreter(Debugger &debugger)
+      : IOHandlerEditline(debugger, IOHandler::Type::LuaInterpreter, "lua",
+                          ">>> ", "..> ", true, debugger.GetUseColor(), 0,
+                          *this, nullptr),
+        m_lua() {}
+
+  void IOHandlerInputComplete(IOHandler &io_handler,
+                              std::string &data) override {
+    if (llvm::Error error = m_lua.Run(data)) {
+      *GetOutputStreamFileSP() << llvm::toString(std::move(error));
+    }
+  }
+
+private:
+  Lua m_lua;
+};
+
 ScriptInterpreterLua::ScriptInterpreterLua(Debugger &debugger)
     : ScriptInterpreter(debugger, eScriptLanguageLua) {}
 
 ScriptInterpreterLua::~ScriptInterpreterLua() {}
 
 bool ScriptInterpreterLua::ExecuteOneLine(llvm::StringRef command,
-                                          CommandReturnObject *,
-                                          const ExecuteScriptOptions &) {
-  m_debugger.GetErrorStream().PutCString(
-      "error: the lua script interpreter is not yet implemented.\n");
-  return false;
+                                          CommandReturnObject *result,
+                                          const ExecuteScriptOptions &options) {
+  Lua l;
+  if (llvm::Error e = l.Run(command)) {
+    result->AppendErrorWithFormatv(
+        "lua failed attempting to evaluate '{0}': {1}\n", command,
+        llvm::toString(std::move(e)));
+    return false;
+  }
+  return true;
 }
 
 void ScriptInterpreterLua::ExecuteInterpreterLoop() {
-  m_debugger.GetErrorStream().PutCString(
-      "error: the lua script interpreter is not yet implemented.\n");
+  static Timer::Category func_cat(LLVM_PRETTY_FUNCTION);
+  Timer scoped_timer(func_cat, LLVM_PRETTY_FUNCTION);
+
+  Debugger &debugger = m_debugger;
+
+  // At the moment, the only time the debugger does not have an input file
+  // handle is when this is called directly from lua, in which case it is
+  // both dangerous and unnecessary (not to mention confusing) to try to embed
+  // a running interpreter loop inside the already running lua interpreter
+  // loop, so we won't do it.
+
+  if (!debugger.GetInputFile().IsValid())
+    return;
+
+  IOHandlerSP io_handler_sp(new IOHandlerLuaInterpreter(debugger));
+  debugger.PushIOHandler(io_handler_sp);
 }
 
 void ScriptInterpreterLua::Initialize() {

lldb/test/CMakeLists.txt

@@ -144,6 +144,7 @@ endif()
 # These values are not canonicalized within LLVM.
 llvm_canonicalize_cmake_booleans(
   LLDB_ENABLE_PYTHON
+  LLDB_ENABLE_LUA
   LLVM_ENABLE_ZLIB
   LLVM_ENABLE_SHARED_LIBS
   LLDB_IS_64_BITS)

lldb/test/Shell/ScriptInterpreter/Lua/lua.test

@@ -0,0 +1,3 @@
+# REQUIRES: lua
+# RUN: %lldb --script-language lua -o 'script print(1000+100+10+1)' 2>&1 | FileCheck %s
+# CHECK: 1111

lldb/test/Shell/lit.cfg.py

@@ -103,6 +103,9 @@ def calculate_arch_features(arch_string):
 if config.lldb_enable_python:
     config.available_features.add('python')
 
+if config.lldb_enable_lua:
+    config.available_features.add('lua')
+
 if config.lldb_enable_lzma:
     config.available_features.add('lzma')
 

lldb/test/Shell/lit.site.cfg.py.in

@@ -19,6 +19,7 @@ config.lldb_enable_lzma = @LLDB_ENABLE_LZMA@
 config.host_triple = "@LLVM_HOST_TRIPLE@"
 config.lldb_bitness = 64 if @LLDB_IS_64_BITS@ else 32
 config.lldb_enable_python = @LLDB_ENABLE_PYTHON@
+config.lldb_enable_lua = @LLDB_ENABLE_LUA@
 config.lldb_build_directory = "@LLDB_TEST_BUILD_DIRECTORY@"
 # The shell tests use their own module caches.
 config.lldb_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_LLDB@", "lldb-shell")

lldb/unittests/ScriptInterpreter/CMakeLists.txt

@@ -1,3 +1,6 @@
 if (LLDB_ENABLE_PYTHON)
   add_subdirectory(Python)
 endif()
+if (LLDB_ENABLE_LUA)
+  add_subdirectory(Lua)
+endif()

lldb/unittests/ScriptInterpreter/Lua/CMakeLists.txt

@@ -0,0 +1,12 @@
+add_lldb_unittest(ScriptInterpreterLuaTests
+  LuaTests.cpp
+  ScriptInterpreterTests.cpp
+
+  LINK_LIBS
+    lldbHost
+    lldbPluginScriptInterpreterLua
+    lldbPluginPlatformLinux
+    LLVMTestingSupport
+  LINK_COMPONENTS
+    Support
+  )

lldb/unittests/ScriptInterpreter/Lua/LuaTests.cpp

@@ -0,0 +1,26 @@
+//===-- LuaTests.cpp ------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "Plugins/ScriptInterpreter/Lua/Lua.h"
+#include "gtest/gtest.h"
+
+using namespace lldb_private;
+
+TEST(LuaTest, RunValid) {
+  Lua lua;
+  llvm::Error error = lua.Run("foo = 1");
+  EXPECT_FALSE(static_cast<bool>(error));
+}
+
+TEST(LuaTest, RunInvalid) {
+  Lua lua;
+  llvm::Error error = lua.Run("nil = foo");
+  EXPECT_TRUE(static_cast<bool>(error));
+  EXPECT_EQ(llvm::toString(std::move(error)),
+            "[string \"buffer\"]:1: unexpected symbol near 'nil'\n");
+}

lldb/unittests/ScriptInterpreter/Lua/ScriptInterpreterTests.cpp

@@ -0,0 +1,62 @@
+//===-- LuaTests.cpp ------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "Plugins/Platform/Linux/PlatformLinux.h"
+#include "Plugins/ScriptInterpreter/Lua/ScriptInterpreterLua.h"
+#include "lldb/Core/Debugger.h"
+#include "lldb/Host/FileSystem.h"
+#include "lldb/Host/HostInfo.h"
+#include "lldb/Interpreter/CommandReturnObject.h"
+#include "lldb/Target/Platform.h"
+#include "lldb/Utility/Reproducer.h"
+#include "gtest/gtest.h"
+
+using namespace lldb_private;
+using namespace lldb_private::repro;
+using namespace lldb;
+
+namespace {
+class ScriptInterpreterTest : public ::testing::Test {
+public:
+  void SetUp() override {
+    llvm::cantFail(Reproducer::Initialize(ReproducerMode::Off, llvm::None));
+    FileSystem::Initialize();
+    HostInfo::Initialize();
+
+    // Pretend Linux is the host platform.
+    platform_linux::PlatformLinux::Initialize();
+    ArchSpec arch("powerpc64-pc-linux");
+    Platform::SetHostPlatform(
+        platform_linux::PlatformLinux::CreateInstance(true, &arch));
+  }
+  void TearDown() override {
+    platform_linux::PlatformLinux::Terminate();
+    HostInfo::Terminate();
+    FileSystem::Terminate();
+    Reproducer::Terminate();
+  }
+};
+} // namespace
+
+TEST_F(ScriptInterpreterTest, Plugin) {
+  EXPECT_EQ(ScriptInterpreterLua::GetPluginNameStatic(), "script-lua");
+  EXPECT_EQ(ScriptInterpreterLua::GetPluginDescriptionStatic(),
+            "Lua script interpreter");
+}
+
+TEST_F(ScriptInterpreterTest, ExecuteOneLine) {
+  DebuggerSP debugger_sp = Debugger::CreateInstance();
+  ASSERT_TRUE(debugger_sp);
+
+  ScriptInterpreterLua script_interpreter(*debugger_sp);
+  CommandReturnObject result;
+  EXPECT_TRUE(script_interpreter.ExecuteOneLine("foo = 1", &result));
+  EXPECT_FALSE(script_interpreter.ExecuteOneLine("nil = foo", &result));
+  EXPECT_TRUE(result.GetErrorData().startswith(
+      "error: lua failed attempting to evaluate 'nil = foo'"));
+}