[lldb] Add a C language REPL to test LLDB's REPL infrastructure

LLDB has a bunch of code that implements REPL support, but all that code is
unreachable as no language in master currently has an implemented REPL backend.
The only REPL that exists is in the downstream Swift fork. All patches for this
generic REPL code therefore also only have tests downstream which is clearly not
a good situation.

This patch implements a basic C language REPL on top of LLDB's REPL framework.
Beside implementing the REPL interface and hooking it up into the plugin
manager, the only other small part of this patch is making the `--language` flag
of the expression command compatible with the `--repl` flag. The `--repl` flag
uses the value of `--language` to see which REPL should be started, but right
now the `--language` flag is only available in OptionGroups 1 and 2, but not in
OptionGroup 3 where the `--repl` flag is declared.

The REPL currently can currently only start if a running target exists. I'll add
the 'create and run a dummy executable' logic from Swift (which is requires when
doing `lldb --repl`) when I have time to translate all this logic to something
that will work with Clang.

I should point out that the REPL currently uses the C expression parser's
approach to persistent variables where only result variables and the ones
starting with a '$' are transferred between expressions. I'll fix that in a
follow up patch. Also the REPL currently doesn't work in a non-interactive
terminal. This seems to be fixed in the Swift fork, so I assume one of our many
REPL downstream changes addresses the issue.

Reviewed By: JDevlieghere

Differential Revision: https://reviews.llvm.org/D87281

diff --git a/lldb/source/Commands/Options.td b/lldb/source/Commands/Options.td
index 67cfc60f9d1b53e094c4fa456acccef51b6eae55..83df2ac22c5786186e2c09993579799d8c7cd556 100644 (file)
--- a/lldb/source/Commands/Options.td
+++ b/lldb/source/Commands/Options.td
@@ -355,7 +355,7 @@ let Command = "expression" in {
     Desc<"When specified, debug the JIT code by setting a breakpoint on the "
     "first instruction and forcing breakpoints to not be ignored (-i0) and no "
     "unwinding to happen on error (-u0).">;
-  def expression_options_language : Option<"language", "l">, Groups<[1,2]>,
+  def expression_options_language : Option<"language", "l">, Groups<[1,2,3]>,
     Arg<"Language">, Desc<"Specifies the Language to use when parsing the "
     "expression.  If not set the target.language setting is used.">;
   def expression_options_apply_fixits : Option<"apply-fixits", "X">,

diff --git a/lldb/source/Plugins/CMakeLists.txt b/lldb/source/Plugins/CMakeLists.txt
index 9181a4e47675fe8254593a1ecbbf542d77d64408..84cc065c3ca5ab8e15583304774594c0799e345b 100644 (file)
--- a/lldb/source/Plugins/CMakeLists.txt
+++ b/lldb/source/Plugins/CMakeLists.txt
@@ -14,6 +14,7 @@ add_subdirectory(ObjectFile)
 add_subdirectory(OperatingSystem)
 add_subdirectory(Platform)
 add_subdirectory(Process)
+add_subdirectory(REPL)
 add_subdirectory(ScriptInterpreter)
 add_subdirectory(StructuredData)
 add_subdirectory(SymbolFile)

diff --git a/lldb/source/Plugins/REPL/CMakeLists.txt b/lldb/source/Plugins/REPL/CMakeLists.txt
new file mode 100644 (file)
index 0000000..17c40ae
--- /dev/null
+++ b/lldb/source/Plugins/REPL/CMakeLists.txt
@@ -0,0 +1 @@
+add_subdirectory(Clang)

diff --git a/lldb/source/Plugins/REPL/Clang/CMakeLists.txt b/lldb/source/Plugins/REPL/Clang/CMakeLists.txt
new file mode 100644 (file)
index 0000000..b995071
--- /dev/null
+++ b/lldb/source/Plugins/REPL/Clang/CMakeLists.txt
@@ -0,0 +1,17 @@
+add_lldb_library(lldbPluginClangREPL PLUGIN
+  ClangREPL.cpp
+
+  LINK_LIBS
+    lldbCore
+    lldbDataFormatters
+    lldbHost
+    lldbSymbol
+    lldbTarget
+    lldbUtility
+    lldbPluginClangCommon
+    lldbPluginCPPRuntime
+    lldbPluginTypeSystemClang
+
+  LINK_COMPONENTS
+    Support
+)

diff --git a/lldb/source/Plugins/REPL/Clang/ClangREPL.cpp b/lldb/source/Plugins/REPL/Clang/ClangREPL.cpp
new file mode 100644 (file)
index 0000000..5060dbb
--- /dev/null
+++ b/lldb/source/Plugins/REPL/Clang/ClangREPL.cpp
@@ -0,0 +1,102 @@
+//===-- ClangREPL.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 "ClangREPL.h"
+#include "lldb/Core/Debugger.h"
+#include "lldb/Core/PluginManager.h"
+#include "lldb/Expression/ExpressionVariable.h"
+
+using namespace lldb_private;
+
+LLDB_PLUGIN_DEFINE(ClangREPL)
+
+ClangREPL::ClangREPL(lldb::LanguageType language, Target &target)
+    : REPL(eKindClang, target), m_language(language),
+      m_implicit_expr_result_regex("\\$[0-9]+") {}
+
+ClangREPL::~ClangREPL() {}
+
+void ClangREPL::Initialize() {
+  LanguageSet languages;
+  // FIXME: There isn't a way to ask CPlusPlusLanguage and ObjCLanguage for
+  // a list of languages they support.
+  languages.Insert(lldb::LanguageType::eLanguageTypeC);
+  languages.Insert(lldb::LanguageType::eLanguageTypeC89);
+  languages.Insert(lldb::LanguageType::eLanguageTypeC99);
+  languages.Insert(lldb::LanguageType::eLanguageTypeC11);
+  languages.Insert(lldb::LanguageType::eLanguageTypeC_plus_plus);
+  languages.Insert(lldb::LanguageType::eLanguageTypeC_plus_plus_03);
+  languages.Insert(lldb::LanguageType::eLanguageTypeC_plus_plus_11);
+  languages.Insert(lldb::LanguageType::eLanguageTypeC_plus_plus_14);
+  languages.Insert(lldb::LanguageType::eLanguageTypeObjC);
+  languages.Insert(lldb::LanguageType::eLanguageTypeObjC_plus_plus);
+  PluginManager::RegisterPlugin(GetPluginNameStatic(), "C language REPL",
+                                &CreateInstance, languages);
+}
+
+void ClangREPL::Terminate() {
+  PluginManager::UnregisterPlugin(&CreateInstance);
+}
+
+lldb::REPLSP ClangREPL::CreateInstance(Status &error,
+                                       lldb::LanguageType language,
+                                       Debugger *debugger, Target *target,
+                                       const char *repl_options) {
+  // Creating a dummy target if only a debugger is given isn't implemented yet.
+  if (!target) {
+    error.SetErrorString("must have a target to create a REPL");
+    return nullptr;
+  }
+  lldb::REPLSP result = std::make_shared<ClangREPL>(language, *target);
+  target->SetREPL(language, result);
+  error = Status();
+  return result;
+}
+
+Status ClangREPL::DoInitialization() { return Status(); }
+
+ConstString ClangREPL::GetSourceFileBasename() {
+  return ConstString("repl.c");
+}
+
+const char *ClangREPL::GetAutoIndentCharacters() { return "  "; }
+
+bool ClangREPL::SourceIsComplete(const std::string &source) {
+  // FIXME: There isn't a good way to know if the input source is complete or
+  // not, so just say that every single REPL line is ready to be parsed.
+  return !source.empty();
+}
+
+lldb::offset_t ClangREPL::GetDesiredIndentation(const StringList &lines,
+                                                int cursor_position,
+                                                int tab_size) {
+  // FIXME: Not implemented.
+  return LLDB_INVALID_OFFSET;
+}
+
+lldb::LanguageType ClangREPL::GetLanguage() { return m_language; }
+
+bool ClangREPL::PrintOneVariable(Debugger &debugger,
+                                 lldb::StreamFileSP &output_sp,
+                                 lldb::ValueObjectSP &valobj_sp,
+                                 ExpressionVariable *var) {
+  // If a ExpressionVariable was passed, check first if that variable is just
+  // an automatically created expression result. These variables are already
+  // printed by the REPL so this is done to prevent printing the variable twice.
+  if (var) {
+    if (m_implicit_expr_result_regex.Execute(var->GetName().GetStringRef()))
+      return true;
+  }
+  valobj_sp->Dump(*output_sp);
+  return true;
+}
+
+void ClangREPL::CompleteCode(const std::string &current_code,
+                             CompletionRequest &request) {
+  // Not implemented.
+}

diff --git a/lldb/source/Plugins/REPL/Clang/ClangREPL.h b/lldb/source/Plugins/REPL/Clang/ClangREPL.h
new file mode 100644 (file)
index 0000000..3666a53
--- /dev/null
+++ b/lldb/source/Plugins/REPL/Clang/ClangREPL.h
@@ -0,0 +1,65 @@
+//===-- ClangREPL.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 LLDB_SOURCE_PLUGINS_REPL_CLANG_CLANGREPL_H
+#define LLDB_SOURCE_PLUGINS_REPL_CLANG_CLANGREPL_H
+
+#include "lldb/Expression/REPL.h"
+
+namespace lldb_private {
+/// Implements a Clang-based REPL for C languages on top of LLDB's REPL
+/// framework.
+class ClangREPL : public REPL {
+public:
+  ClangREPL(lldb::LanguageType language, Target &target);
+
+  ~ClangREPL() override;
+
+  static void Initialize();
+
+  static void Terminate();
+
+  static lldb::REPLSP CreateInstance(Status &error, lldb::LanguageType language,
+                                     Debugger *debugger, Target *target,
+                                     const char *repl_options);
+
+  static lldb_private::ConstString GetPluginNameStatic() {
+    return ConstString("ClangREPL");
+  }
+
+protected:
+  Status DoInitialization() override;
+
+  ConstString GetSourceFileBasename() override;
+
+  const char *GetAutoIndentCharacters() override;
+
+  bool SourceIsComplete(const std::string &source) override;
+
+  lldb::offset_t GetDesiredIndentation(const StringList &lines,
+                                       int cursor_position,
+                                       int tab_size) override;
+
+  lldb::LanguageType GetLanguage() override;
+
+  bool PrintOneVariable(Debugger &debugger, lldb::StreamFileSP &output_sp,
+                        lldb::ValueObjectSP &valobj_sp,
+                        ExpressionVariable *var = nullptr) override;
+
+  void CompleteCode(const std::string &current_code,
+                    CompletionRequest &request) override;
+
+private:
+  /// The specific C language of this REPL.
+  lldb::LanguageType m_language;
+  /// A regex matching the implicitly created LLDB result variables.
+  lldb_private::RegularExpression m_implicit_expr_result_regex;
+};
+} // namespace lldb_private
+
+#endif // LLDB_SOURCE_PLUGINS_REPL_CLANG_CLANGREPL_H

diff --git a/lldb/test/API/repl/clang/Makefile b/lldb/test/API/repl/clang/Makefile
new file mode 100644 (file)
index 0000000..c9319d6
--- /dev/null
+++ b/lldb/test/API/repl/clang/Makefile
@@ -0,0 +1,2 @@
+C_SOURCES := main.c
+include Makefile.rules

diff --git a/lldb/test/API/repl/clang/TestClangREPL.py b/lldb/test/API/repl/clang/TestClangREPL.py
new file mode 100644 (file)
index 0000000..6fd89a0
--- /dev/null
+++ b/lldb/test/API/repl/clang/TestClangREPL.py
@@ -0,0 +1,54 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.lldbpexpect import PExpectTest
+
+class TestCase(PExpectTest):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def expect_repl(self, expr, substrs=[]):
+        """ Evaluates the expression in the REPL and verifies that the list
+        of substrs is in the REPL output."""
+        # Only single line expressions supported.
+        self.assertNotIn("\n", expr)
+        self.child.send(expr + "\n")
+        for substr in substrs:
+            self.child.expect_exact(substr)
+        # Look for the start of the next REPL input line.
+        self.current_repl_line_number += 1
+        self.child.expect_exact(str(self.current_repl_line_number) + ">")
+
+    # PExpect uses many timeouts internally and doesn't play well
+    # under ASAN on a loaded machine..
+    @skipIfAsan
+    @skipIfEditlineSupportMissing
+    def test_basic_completion(self):
+        """Test that we can complete a simple multiline expression"""
+        self.build()
+        self.current_repl_line_number = 1
+
+        self.launch(executable=self.getBuildArtifact("a.out"), dimensions=(100,500))
+        # Try launching the REPL before we have a running target.
+        self.expect("expression --repl -l c --", substrs=["REPL requires a running target process."])
+
+        self.expect("b main", substrs=["Breakpoint 1", "address ="])
+        self.expect("run", substrs=["stop reason = breakpoint 1"])
+
+        # Start the REPL.
+        self.child.send("expression --repl -l c --\n")
+        self.child.expect_exact("1>")
+
+        # Try evaluating a simple expression.
+        self.expect_repl("3 + 3", substrs=["(int) $0 = 6"])
+
+        # Try declaring a persistent variable.
+        self.expect_repl("long $persistent = 7; 5",
+                         substrs=["(int) $1 = 5",
+                                  "(long) $persistent = 7"])
+
+        # Try using the persistent variable from before.
+        self.expect_repl("$persistent + 10",
+                         substrs=["(long) $2 = 17"])
+
+        self.quit()

diff --git a/lldb/test/API/repl/clang/main.c b/lldb/test/API/repl/clang/main.c
new file mode 100644 (file)
index 0000000..5c2fa9b
--- /dev/null
+++ b/lldb/test/API/repl/clang/main.c
@@ -0,0 +1,3 @@
+int main(int argc, char **argv) {
+  return 0;
+}