HackStudio: Add cpp debugger

The HackStudio debugger integrates with LibDebug to provide
source-level debugging.

The user can set breakpoints at various positions in the source code,
and then run the program in debug mode.

When the program is stopped, the current execution position is
displayed, and the user can insert/remove breakpoints, continue
execution, or single step the program.

Base/home/anon/little/Makefile

@@ -1,5 +1,6 @@
 PROGRAM = little
 OBJS = main.o
+CXXFLAGS = -g
 
 all: $(PROGRAM)
 

DevTools/HackStudio/Debugger.cpp

@@ -0,0 +1,180 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Debugger.h"
+
+static Debugger* s_the;
+
+Debugger& Debugger::the()
+{
+    ASSERT(s_the);
+    return *s_the;
+}
+
+void Debugger::initialize(
+    Function<void(DebugInfo::SourcePosition)> on_stop_callback,
+    Function<void()> on_continue_callback,
+    Function<void()> on_exit_callback)
+{
+    s_the = new Debugger(move(on_stop_callback), move(on_continue_callback), move(on_exit_callback));
+}
+
+bool Debugger::is_initialized()
+{
+    return s_the;
+}
+
+Debugger::Debugger(
+    Function<void(DebugInfo::SourcePosition)> on_stop_callback,
+    Function<void()> on_continue_callback,
+    Function<void()> on_exit_callback)
+    : m_on_stopped_callback(move(on_stop_callback))
+    , m_on_continue_callback(move(on_continue_callback))
+    , m_on_exit_callback(move(on_exit_callback))
+{
+    pthread_mutex_init(&m_continue_mutex, nullptr);
+    pthread_cond_init(&m_continue_cond, nullptr);
+}
+
+void Debugger::on_breakpoint_change(const String& file, size_t line, BreakpointChange change_type)
+{
+    auto position = create_source_position(file, line);
+
+    if (change_type == BreakpointChange::Added) {
+        Debugger::the().m_breakpoints.append(position);
+    } else {
+        Debugger::the().m_breakpoints.remove_all_matching([&](DebugInfo::SourcePosition val) { return val == position; });
+    }
+
+    auto session = Debugger::the().session();
+    if (!session)
+        return;
+
+    auto address = session->debug_info().get_instruction_from_source(position.file_path, position.line_number);
+    if (!address.has_value())
+        return;
+
+    if (change_type == BreakpointChange::Added) {
+        bool success = session->insert_breakpoint(reinterpret_cast<void*>(address.value()));
+        ASSERT(success);
+    } else {
+        bool success = session->remove_breakpoint(reinterpret_cast<void*>(address.value()));
+        ASSERT(success);
+    }
+}
+
+DebugInfo::SourcePosition Debugger::create_source_position(const String& file, size_t line)
+{
+    return { String::format("./%s", file.characters()), line + 1 };
+}
+
+int Debugger::start_static()
+{
+    Debugger::the().start();
+    return 0;
+}
+
+void Debugger::start()
+{
+    m_debug_session = DebugSession::exec_and_attach(m_executable_path);
+    ASSERT(!!m_debug_session);
+
+    for (const auto& breakpoint : m_breakpoints) {
+        dbg() << "insertig breakpoint at: " << breakpoint.file_path << ":" << breakpoint.line_number;
+        auto address = m_debug_session->debug_info().get_instruction_from_source(breakpoint.file_path, breakpoint.line_number);
+        if (address.has_value()) {
+            bool success = m_debug_session->insert_breakpoint(reinterpret_cast<void*>(address.value()));
+            ASSERT(success);
+        } else {
+            dbg() << "couldn't insert breakpoint";
+        }
+    }
+
+    debugger_loop();
+}
+
+int Debugger::debugger_loop()
+{
+    bool in_single_step_mode = false;
+    Vector<void*> temporary_breakpoints;
+
+    m_debug_session->run([&](DebugSession::DebugBreakReason reason, Optional<PtraceRegisters> optional_regs) {
+        if (reason == DebugSession::DebugBreakReason::Exited) {
+            dbg() << "Program exited";
+            m_on_exit_callback();
+            return DebugSession::DebugDecision::Detach;
+        }
+        ASSERT(optional_regs.has_value());
+        const PtraceRegisters& regs = optional_regs.value();
+        auto source_position = m_debug_session->debug_info().get_source_position(regs.eip);
+        if (!source_position.has_value()) {
+            return DebugSession::DebugDecision::Continue;
+        }
+
+        if (in_single_step_mode) {
+            for (auto address : temporary_breakpoints) {
+                m_debug_session->remove_breakpoint(address);
+            }
+            temporary_breakpoints.clear();
+            in_single_step_mode = false;
+        }
+
+        dbg() << "Debugee stopped @ " << source_position.value().file_path << ":" << source_position.value().line_number;
+        m_on_stopped_callback(source_position.value());
+
+        pthread_mutex_lock(&m_continue_mutex);
+        pthread_cond_wait(&m_continue_cond, &m_continue_mutex);
+        pthread_mutex_unlock(&m_continue_mutex);
+
+        m_on_continue_callback();
+
+        if (m_continue_type == ContinueType::Continue) {
+            return DebugSession::DebugDecision::Continue;
+        }
+
+        if (m_continue_type == ContinueType::SourceSingleStep) {
+            // A possible method for source level single stepping is to single step
+            // in assembly level, until the current instruction's source position has changed.
+            // However, since we do not currently generate debug symbols for library code,
+            // we may have to single-step over lots of library code instructions until we get back to our code,
+            // which is very slow.
+            // So the current method is to insert a temporary breakpoint at every known statement in our source code,
+            // continue execution, and remove the temporary breakpoints once we hit the first breakpoint.
+            m_debug_session->debug_info().for_each_source_position([&](DebugInfo::SourcePosition position) {
+                auto address = (void*)position.address_of_first_statement;
+                if ((u32)address != regs.eip && !m_debug_session->breakpoint_exists(address)) {
+                    m_debug_session->insert_breakpoint(address);
+                    temporary_breakpoints.append(address);
+                }
+            });
+            in_single_step_mode = true;
+            return DebugSession::DebugDecision::Continue;
+        }
+        ASSERT_NOT_REACHED();
+    });
+    m_debug_session.clear();
+    return 0;
+}

DevTools/HackStudio/Debugger.h

@@ -0,0 +1,90 @@
+
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+#include "BreakpointCallback.h"
+#include <AK/Function.h>
+#include <AK/Vector.h>
+#include <LibDebug/DebugSession.h>
+#include <LibThread/Lock.h>
+#include <LibThread/Thread.h>
+
+class Debugger {
+public:
+    static Debugger& the();
+    static void initialize(
+        Function<void(DebugInfo::SourcePosition)> on_stop_callback,
+        Function<void()> on_continue_callback,
+        Function<void()> on_exit_callback);
+
+    static bool is_initialized();
+
+    static void on_breakpoint_change(const String& file, size_t line, BreakpointChange change_type);
+
+    void set_executable_path(const String& path) { m_executable_path = path; }
+
+    DebugSession* session() { return m_debug_session.ptr(); }
+
+    // Thread entry point
+    static int start_static();
+
+    pthread_mutex_t* continue_mutex() { return &m_continue_mutex; }
+    pthread_cond_t* continue_cond() { return &m_continue_cond; }
+
+    enum class ContinueType {
+        Continue,
+        SourceSingleStep,
+    };
+
+    void set_continue_type(ContinueType type) { m_continue_type = type; }
+    void reset_breakpoints() { m_breakpoints.clear(); }
+
+private:
+    explicit Debugger(
+        Function<void(DebugInfo::SourcePosition)> on_stop_callback,
+        Function<void()> on_continue_callback,
+        Function<void()> on_exit_callback);
+
+    static DebugInfo::SourcePosition create_source_position(const String& file, size_t line);
+
+    void start();
+    int debugger_loop();
+
+    OwnPtr<DebugSession> m_debug_session;
+
+    pthread_mutex_t m_continue_mutex {};
+    pthread_cond_t m_continue_cond {};
+
+    Vector<DebugInfo::SourcePosition> m_breakpoints;
+    String m_executable_path;
+
+    Function<void(DebugInfo::SourcePosition)> m_on_stopped_callback;
+    Function<void()> m_on_continue_callback;
+    Function<void()> m_on_exit_callback;
+
+    ContinueType m_continue_type { ContinueType::Continue };
+};

DevTools/HackStudio/Makefile

@@ -13,10 +13,11 @@ OBJS = \
     CursorTool.o \
     WidgetTool.o \
     WidgetTreeModel.o \
+    Debugger.o \
     main.o
 
 PROGRAM = HackStudio
 
-LIB_DEPS = GUI Web VT Protocol Markdown Gfx IPC Thread Pthread Core JS
+LIB_DEPS = GUI Web VT Protocol Markdown Gfx IPC Thread Pthread Core JS Debug
 
 include ../../Makefile.common

DevTools/HackStudio/Project.h

@@ -56,6 +56,8 @@ public:
     ProjectType type() const { return m_type; }
     GUI::Model& model() { return *m_model; }
     String default_file() const;
+    String name() const { return m_name; }
+    String path() const { return m_path; }
 
     template<typename Callback>
     void for_each_text_file(Callback callback) const

DevTools/HackStudio/main.cpp

@@ -25,6 +25,7 @@
  */
 
 #include "CursorTool.h"
+#include "Debugger.h"
 #include "Editor.h"
 #include "EditorWrapper.h"
 #include "FindInFilesWidget.h"
@@ -36,7 +37,10 @@
 #include "WidgetTool.h"
 #include "WidgetTreeModel.h"
 #include <AK/StringBuilder.h>
+#include <LibCore/Event.h>
+#include <LibCore/EventLoop.h>
 #include <LibCore/File.h>
+#include <LibDebug/DebugSession.h>
 #include <LibGUI/AboutDialog.h>
 #include <LibGUI/Action.h>
 #include <LibGUI/ActionGroup.h>
@@ -62,6 +66,8 @@
 #include <LibGUI/TreeView.h>
 #include <LibGUI/Widget.h>
 #include <LibGUI/Window.h>
+#include <LibThread/Lock.h>
+#include <LibThread/Thread.h>
 #include <LibVT/TerminalWidget.h>
 #include <stdio.h>
 #include <sys/wait.h>
@@ -84,7 +90,7 @@ static RefPtr<GUI::TabWidget> s_action_tab_widget;
 
 void add_new_editor(GUI::Widget& parent)
 {
-    auto wrapper = EditorWrapper::construct();
+    auto wrapper = EditorWrapper::construct(Debugger::on_breakpoint_change);
     if (s_action_tab_widget) {
         parent.insert_child_before(wrapper, *s_action_tab_widget);
     } else {
@@ -120,6 +126,24 @@ Editor& current_editor()
     return current_editor_wrapper().editor();
 }
 
+NonnullRefPtr<EditorWrapper> get_editor_of_file(const String& file)
+{
+    for (auto& wrapper : g_all_editor_wrappers) {
+        String wrapper_file = wrapper.filename_label().text();
+        if (wrapper_file == file || String::format("./%s", wrapper_file.characters()) == file) {
+            return wrapper;
+        }
+    }
+    ASSERT_NOT_REACHED();
+}
+
+String get_project_executable_path()
+{
+    // e.g /my/project.files => /my/project
+    // TODO: Perhaps a Makefile rule for getting the value of $(PROGRAM) would be better?
+    return g_project->path().substring(0, g_project->path().index_of(".").value());
+}
+
 static void build(TerminalWrapper&);
 static void run(TerminalWrapper&);
 void open_project(String);
@@ -531,13 +555,78 @@ int main(int argc, char** argv)
         run(terminal_wrapper);
         stop_action->set_enabled(true);
     });
+
+    RefPtr<LibThread::Thread> debugger_thread;
+    auto debug_action = GUI::Action::create("Debug", Gfx::Bitmap::load_from_file("/res/icons/16x16/play-debug.png"), [&](auto&) {
+        if (g_project->type() != ProjectType::Cpp) {
+            GUI::MessageBox::show(String::format("Cannot debug current project type", get_project_executable_path().characters()), "Error", GUI::MessageBox::Type::Error, GUI::MessageBox::InputType::OK, g_window);
+            return;
+        }
+        if (!GUI::FilePicker::file_exists(get_project_executable_path())) {
+            GUI::MessageBox::show(String::format("Could not find file: %s. (did you build the project?)", get_project_executable_path().characters()), "Error", GUI::MessageBox::Type::Error, GUI::MessageBox::InputType::OK, g_window);
+            return;
+        }
+        if (Debugger::the().session()) {
+            GUI::MessageBox::show("Debugger is already running", "Error", GUI::MessageBox::Type::Error, GUI::MessageBox::InputType::OK, g_window);
+            return;
+        }
+        Debugger::the().set_executable_path(get_project_executable_path());
+        debugger_thread = adopt(*new LibThread::Thread(Debugger::start_static));
+        debugger_thread->start();
+    });
+
+    auto continue_action = GUI::Action::create("Continue", Gfx::Bitmap::load_from_file("/res/icons/16x16/go-last.png"), [&](auto&) {
+        pthread_mutex_lock(Debugger::the().continue_mutex());
+        Debugger::the().set_continue_type(Debugger::ContinueType::Continue);
+        pthread_cond_signal(Debugger::the().continue_cond());
+        pthread_mutex_unlock(Debugger::the().continue_mutex());
+    });
+
+    auto single_step_action = GUI::Action::create("Single Step", Gfx::Bitmap::load_from_file("/res/icons/16x16/single-step.png"), [&](auto&) {
+        pthread_mutex_lock(Debugger::the().continue_mutex());
+        Debugger::the().set_continue_type(Debugger::ContinueType::SourceSingleStep);
+        pthread_cond_signal(Debugger::the().continue_cond());
+        pthread_mutex_unlock(Debugger::the().continue_mutex());
+    });
+    continue_action->set_enabled(false);
+    single_step_action->set_enabled(false);
+
     toolbar.add_action(run_action);
     toolbar.add_action(stop_action);
+    toolbar.add_action(debug_action);
+    toolbar.add_action(continue_action);
+    toolbar.add_action(single_step_action);
+
+    RefPtr<EditorWrapper> current_editor_in_execution;
+    Debugger::initialize(
+        [&](DebugInfo::SourcePosition source_position) {
+            dbg() << "Program stopped";
+            current_editor_in_execution = get_editor_of_file(source_position.file_path);
+            current_editor_in_execution->editor().set_execution_position(source_position.line_number - 1);
+            continue_action->set_enabled(true);
+            single_step_action->set_enabled(true);
+        },
+        [&]() {
+            dbg() << "Program continued";
+            continue_action->set_enabled(false);
+            single_step_action->set_enabled(false);
+            if (current_editor_in_execution) {
+                current_editor_in_execution->editor().clear_execution_position();
+            }
+        },
+        [&]() {
+            dbg() << "Program exited";
+            Core::EventLoop::main().post_event(*g_window, make<Core::DeferredInvocationEvent>([=](auto&) {
+                GUI::MessageBox::show("Program Exited", "Debugger", GUI::MessageBox::Type::Information, GUI::MessageBox::InputType::OK, g_window);
+            }));
+            Core::EventLoop::wake();
+        });
 
     auto& build_menu = menubar->add_menu("Build");
     build_menu.add_action(build_action);
     build_menu.add_action(run_action);
     build_menu.add_action(stop_action);
+    build_menu.add_action(debug_action);
 
     auto& view_menu = menubar->add_menu("View");
     view_menu.add_action(hide_action_tabs_action);
@@ -613,6 +702,9 @@ void open_project(String filename)
         g_project_tree_view->toggle_index(g_project_tree_view->model()->index(0, 0));
         g_project_tree_view->update();
     }
+    if (Debugger::is_initialized()) {
+        Debugger::the().reset_breakpoints();
+    }
 }
 
 void open_file(const String& filename)