path: root/doc/qtcreator/src/debugger/creator-only/creator-debugger.qdoc

// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

// **********************************************************************
// NOTE: the sections are not ordered by their logical order to avoid
// reshuffling the file each time the index order changes (i.e., often).
// Run the fixnavi.pl script to adjust the links to the index order.
// **********************************************************************

/*!
    \previouspage creator-testing.html
    \page creator-debugging.html
    \nextpage creator-debugger-engines.html

    \title Debugging

    A debugger lets you see what happens \e inside an application while it runs
    or when it crashes. A debugger can do the following to help you find errors
    in the application:

    \list
        \li Start the application with parameters that specify its behavior.
        \li Stop the application when conditions are met.
        \li Examine what happens when the application stops.
        \li Make changes in the application when you fix an error and continue
            to find the next one.
    \endlist

    The \QC debugger plugin acts as an interface between the \QC
    core and external native debuggers that you can use to:

    \list
        \li Debug executable binary files - GNU Symbolic Debugger (GDB),
            the Microsoft Console Debugger (CDB), and the debugger of the
            low level virtual machine (LLVM) project, LLDB.
        \li Debug QML and Java code and Qt Quick applications -
            QML/JavaScript debugger.
        \li Debug Python source code - PDB.
    \endlist

    The following sections describe how to set up, launch, and interact with the
    debugger:

    \list

        \li \l{Setting Up Debugger}

            The debugger plugin automatically selects a suitable
            native debugger for each \l{glossary-buildandrun-kit}{kit} from the
            ones found on your system. You can edit the kits to override this
            choice.

        \li \l{Launching the Debugger}

            To start an application from an open project under the control
            of a debugger, select the \inlineimage icons/qtcreator-debug-button.png
            (\uicontrol {Start Debugging of Startup Project}) button or press
            \key F5. Other, less common start options are available in the
            \uicontrol Debug > \uicontrol {Start Debugging} menu.

        \li \l{Debug Mode Views}

            Use the views in the \uicontrol Debug mode to inspect the
            state of your application while debugging.

        \li \l{Stopping Applications}

            You can interrupt a running application before it terminates
            or to find out why the application does not work correctly.
            Set breakpoints to stop the application for examining and changing
            variables, setting new breakpoints or removing old ones, and then
            continue running the application.

        \li \l{Examining Data}

            You can examine variable values and data structures in detail.

        \li \l{Remote Debugging}

            You can debug an application that runs on a remote target with the
            necessary helper processes also running.

        \li \l{Debugger Preferences}

            Specify preferences for managing debugger processes. You can specify
            preferences that are common to all debuggers, or the native debugger
            that you use, GDB or CDB.

        \li \l{Using Debugging Helpers}

            \QC is able to show complex data types in a customized,
            user-extensible manner. For this purpose, it takes advantage of
            two technologies, collectively referred to as \e {debugging
            helpers}.

        \li \l{Debugging Qt Quick Projects}

            When debugging a Qt Quick application, you can inspect the state of
            the application while debugging JavaScript functions. You can set
            breakpoints, view call stack trace, and examine locals and
            expressions. While the application is running, you can inspect QML
            objects and user interfaces, as well as execute JavaScript
            expressions.

        \li \l{Debugging a C++ Example Application}

            Illustrates how to debug C++ applications in \QC.

        \li \l{Debugging a Qt Quick Example Application}

            Illustrates how to debug Qt Quick applications in \QC.

        \li \l{Troubleshooting Debugger}

            If you encounter problems while debugging, check for possible
            solutions to them.
    \endlist

    \sa {Debug CMake project files}
*/


/*!
    \previouspage creator-debugger-engines.html
    \page creator-debugger-operating-modes.html
    \nextpage creator-debug-mode.html

    \title Launching the Debugger

    To start an application from an open project under the control of a
    debugger, select the \inlineimage icons/qtcreator-debug-button.png
    (\uicontrol {Start Debugging of Startup Project}) button or press \key F5.

    \QC checks whether the compiled application is up-to-date, and rebuilds and
    deploys it if you set the \uicontrol {Build before deploying} field to
    build the whole project or the application to run and select the
    \uicontrol {Always deploy before running} check box in \preferences >
    \uicontrol {Build & Run} > \uicontrol General. To debug the application
    without deploying it, select \uicontrol Debug > \uicontrol {Start Debugging}
    > \uicontrol {Start Debugging Without Deployment}.

    The debugger then takes over and starts the application with suitable
    parameters.

    When using GDB or CDB as debug backend, you can specify additional commands
    to execute before and after the backend and debugged application are started or
    attached in \preferences > \uicontrol Debugger >
    \uicontrol GDB and \uicontrol CDB. For more information, see
    \l{Debugger Preferences}.

    To let the debugger read the user's default .gdbinit file when it starts,
    select the \uicontrol {Load .gdbinit file on startup} check box in
    GDB settings. For more information, see \l{Specifying GDB Settings}.

    \note Starting a C++ application under the control of the debugger can take
    a long time. Typically, in the range of several seconds to minutes if you use
    complex features.

    For \l {Creating a Qt for Python Application with Qt Widgets}{Python} projects,
    start debugging the \c main.py file. If you encounter problems, check the
    active build target in the \l{Building for Multiple Platforms}{kit selector}.

    \section1 Debugger Operating Modes

    The debugger plugin can run the native debuggers in various operating modes
    depending on where and how you start and run the debugged process. Some of
    the modes are only available for a particular operating system or platform.

    In general, \key F5 and the \uicontrol {Start Debugging of Startup Project}
    button start the operating mode that fits the context. So, for a C++
    application that uses the \MinGW toolchain targeting desktop Windows, the GDB
    engine starts in \e {start internal} mode. For a QML application that uses C++
    plugins, a \e mixed QML/C++ engine starts, with the C++ parts being
    handled by GDB and GDB server remote debugging.

    Change the run configuration parameters (such as
    \uicontrol {Run in Terminal}) in the run settings of the project, or select
    options from the \uicontrol Debug > \uicontrol {Start Debugging} menu to
    select other modes of operation.

    The debugger can run in the following modes:

    \list

       \li \e{Start internal} to debug applications developed inside \QC, such as
            a Qt Widgets-based application.

       \li \e{Start external} to start and debug processes without a proper \QC
            project setup, either locally or on a remote machine.

       \li \e{Attach} to debug processes already started and running outside
            \QC, either locally or on a remote machine.

       \li \e{Core} to debug crashed processes on Unix.

       \li \e{Post-mortem} to debug crashed processes on Windows.

    \endlist

    \section2 Start Internal

    Start internal mode is the default start mode for most projects, including
    all projects using a desktop Qt version and plain C++ projects.

    If you need a console window to operate your application, for example
    because it accepts console input from the user, go to \uicontrol Projects >
    \uicontrol {Run Settings} and select the \uicontrol {Run in terminal} check
    box.

    If a console application does not start up properly in the configured
    console and the subsequent attach fails, you can diagnose the issue by
    using CDB's native console. Select \preferences >
    \uicontrol Debugger > \uicontrol CDB > \uicontrol {Use CDB console} to
    override the console set in the Windows system environment variables.
    Note that the native console does not prompt on application exit.

    To launch the debugger in start internal mode, click the
    \uicontrol {Start Debugging} button for the active project.

    You can specify breakpoints before or after launching the debugger.
    For more information, see \l{Setting Breakpoints}.

    \section2 Start External

    You can debug any executable on your local or on a remote
    machine without using a project. You specify a build and run kit that
    identifies the device to debug the application on.

    While this mode does not strictly require a project to be open in \QC,
    opening it makes setting breakpoints and stepping through the code easier.

    To start and debug an external application:

    \list 1
        \li Select \uicontrol Debug > \uicontrol {Start Debugging} >
            \uicontrol {Start and Debug External Application}.
        \image qtcreator-debugger-start-external.png
        \li In the \uicontrol Kit field, select the build and run kit to
            use for building the project.
        \li In the \uicontrol {Local executable} field, specify the path to the
            application executable on the local machine.
        \li In the \uicontrol {Command line arguments} field, specify command
            line arguments to be passed to the executable.
        \li In the \uicontrol {Working directory} field, specify the working
            directory. It defaults to the directory of the build result.
        \li Select the \uicontrol{Run in terminal} check box for console
            applications.
        \li Select the \uicontrol {Break at "main"} check box to stop the
            debugger at the main function.
        \li Select the \uicontrol {Use target extended-remote to connect}
            check box to create the connection in the
            \c {target extended-remote mode}. In this mode, when the debugged
            application exits or you detach from it, the debugger remains
            connected to the target. You can rerun the application, attach
            to a running application, or use monitor commands specific to the
            target. For example, GDB does not exit unless it was invoked using
            the \c {--once} option, but you can make it exit by using the
            \c {monitor exit} command.
        \li In the \uicontrol {Override SysRoot} field, specify the path to
            the \c sysroot to use instead of the default \c sysroot.
        \li In the \uicontrol {Debug information} field, specify the location
            for storing debug information. You cannot use an empty path.
        \li In the \uicontrol Recent field, you can select a recent
            configuration to use.
    \endlist

    \section2 Attach

    You can attach the debugger to applications that are already running or
    instruct the debugger to attach to an application when it starts.

    \section3 Attaching to Running Applications

    To attach the debugger to an application already running on your local or on
    a remote machine:

    \list 1
        \li Select \uicontrol Debug > \uicontrol {Start Debugging} >
            \uicontrol {Attach to Running Application}.
            \image qtcreator-debugger-attach-to-running.png
        \li In the \uicontrol Filter field, enter a string to filter processes
            by their process ID or name.
        \li Select a process in the list, and then select
            \uicontrol {Attach to Process} to start debugging.
    \endlist

    To refresh the list of running processes, select \uicontrol {Update List}.

    To terminate the selected process, select \uicontrol {Kill Process}.

    While this mode does not strictly require a project to be open in \QC,
    opening it makes setting breakpoints and stepping through the code easier.

    You can specify breakpoints before or after attaching the debugger to the
    application. For more information, see \l{Setting Breakpoints}.

    \section3 Attaching to Processes when They Start

    To instruct the debugger to watch an application process and to attach
    to it when it starts:

    \list 1
        \li Select \uicontrol Debug > \uicontrol {Start Debugging} >
            \uicontrol {Attach to Unstarted Application}.
            \image qtcreator-debugger-attach-to-process-not-yet-started.png
        \li In the \uicontrol Kit field, select the build and run kit to
            use for building the project.
        \li In the \uicontrol Executable field, specify the path to the
            application executable.
        \li Select the \uicontrol {Reopen dialog when application finishes}
            check box to return to this dialog when the application is closed.
        \li Select the \uicontrol {Continue on attach} check box to instruct
            the debugger to keep the application running after attaching to it.
        \li Select \uicontrol {Start Watching} to wait for the application
            process to start.
    \endlist

    \section2 Core

    Use the core mode to inspect \e {core} files (crash dumps) that are
    generated from crashed processes on Linux and Unix systems if the system is
    set up to allow this.

    To enable the dumping of core files on a Unix system, enter the following
    command in the shell from which the application is launched:

    \code
    ulimit -c unlimited
    \endcode

    To launch the debugger in the core mode:

    \list 1
        \li Select \uicontrol Debug > \uicontrol {Start Debugging} >
            \uicontrol {Load Core File}.
            \image qtcreator-debugger-load-core-file.png
        \li In the \uicontrol Kit field, select a build and run kit that was
            used for building the binary for which the core file was created.
            If the core file stems from a binary not built by \QC or a process
            not initiated by \QC, select a kit that matches the setup used as
            closely as possible, in respect to the specified device, tool chain,
            debugger, and sysroot.
        \li In the \uicontrol {Core file} field, specify the core file to
            inspect.
        \li In the \uicontrol {Executable of symbol file} field, specify
            a file that has debug information corresponding to the
            core file. Typically, this is the executable file or a \c {.debug}
            file if the debug information is stored separately from the
            executable.
        \li In the \uicontrol {Override start script} field, specify a
            script file to run instead of the default start script.
        \li In the \uicontrol {Override SysRoot} field, specify the path to
            the \c sysroot to use instead of the default \c sysroot.
    \endlist

    Even though using a properly configured project that has the sources of the
    crashed application is not strictly necessary, it is helpful.

    \section2 Post-Mortem

    The post-mortem mode is available only on Windows, if you installed the
    debugging tools for Windows.

    The \QC installation program asks you whether you want to register \QC as a
    post-mortem debugger. To change the setting, select
    \preferences > \uicontrol Debugger >
    \uicontrol General > \uicontrol {Use \QC for post-mortem debugging}.

    You can launch the debugger in the post-mortem mode if an application
    crashes on Windows. Click the \uicontrol {Debug in \QC} button in the error
    message from the Windows operating system.

    \section1 Starting the Debugger from the Command Line

    You can use the \QC debugger interface from the command line. To attach it
    to a running process, specify the process ID as a parameter for the
    \c {-debug} option. To examine a core file, specify the file name. \QC
    executes all the necessary steps, such as searching for the binary that
    belongs to a core file. To connect to a debug server, specify the server
    location and port number.

    For example:

    \list

        \li  \c {C:\qtcreator\bin>qtcreator -debug 2000}
        \li  \c {C:\qtcreator\bin>qtcreator -debug core=core.2000}
        \li  \c {C:\qtcreator\bin>qtcreator -debug some.exe,core=core}
        \li  \c {C:\qtcreator\bin>qtcreator -debug server=some.dot.com:4251}

    \endlist

    For more information, see \l{Command-Line Options}.
*/

/*!
    \page creator-remote-debugging.html
    \previouspage creator-debugger-examining-data.html
    \nextpage creator-debugger-preferences.html

    \title Remote Debugging

    \QC makes remote debugging easy.
    In general, the remote debugging setup consist of a probe running on the
    remote machine and a counterpart running on the host side. The probe is
    either integrated into the running process (e.g. for QML debugging) or runs
    a separate process (e.g. when using GDB server on embedded Linux). The host
    side typically consists of \QC itself, often with the help of an external
    process, such as GDB or CDB.

    While this setup might look daunting, it is mostly invisible to the user of
    \QC. To start debugging on a remote target with the necessary helper
    processes running, select the corresponding
    \l{glossary-buildandrun-kit}{kit} in \uicontrol Projects >
    \uicontrol {Build & Run}, and then select a function to start remote
    debugging in the \uicontrol Debug > \uicontrol {Start Debugging} menu.

    Special use cases, such as attaching to a running process on the target,
    might still require manual setup.

    \section1 Using GDB

    When debugging on a target supported by GDB server, a local GDB process
    talks to a GDB server running on the remote machine that controls the
    process to be debugged.

    The GDB server process is started on the remote machines by passing a port
    number and the executable:

    \code
    gdbserver :1234 <executable>
    \endcode

    It then typically responds:
    \code
    Process bin/qtcreator created; pid = 5159
    Listening on port 1234
    \endcode

    On the local machine that runs \QC:

    \list 1

        \li Select \uicontrol Debug > \uicontrol {Start Debugging} >
            \uicontrol {Attach to Running Debug Server}.
            \image qtcreator-debugger-attach-to-running-debug-server.png
        \li In the \uicontrol Kit field, select the build and run kit to
            use for building the project.
        \li In the \uicontrol {Server port} field, enter the name of the remote
            machine and the port number to use.
        \li In the \uicontrol {Local executable} field, specify the path to the
            application executable on the local machine.
        \li In the \uicontrol {Command line arguments} field, specify command
            line arguments to be passed to the executable.
        \li In the \uicontrol {Working directory} field, specify the working
            directory. It defaults to the directory of the build result.
        \li Select the \uicontrol{Run in terminal} check box for console
            applications.
        \li Select the \uicontrol {Break at "main"} check box to stop the
            debugger at the main function.
        \li Select the \uicontrol {Use target extended-remote to connect}
            check box to create the connection in the
            \c {target extended-remote mode}. In this mode, when the debugged
            application exits or you detach from it, the debugger remains
            connected to the target. You can rerun the application, attach
            to a running application, or use monitor commands specific to the
            target. For example, GDB does not exit unless it was invoked using
            the \c {--once} option, but you can make it exit by using the
            \c {monitor exit} command.
        \li In the \uicontrol {Override SysRoot} field, specify the path to
            the \c sysroot to use instead of the default \c sysroot.
        \li In the \uicontrol {Init commands} field, enter the commands
            to execute immediately after the connection to a target has
            been established.
        \li In the \uicontrol {Reset commands} field, enter the commands
            to execute when resetting the connection to a target.
        \li In the \uicontrol {Debug information} field, specify the location
            for storing debug information. You cannot use an empty path.
        \li In the \uicontrol {Override server channel} field, specify a
            communication channel to use, such as a serial line or custom port.
        \li In the \uicontrol Recent field, you can select a recent
            configuration to use.
        \li Select \uicontrol OK to start debugging.

    \endlist

    By default, a non-responsive GDB process is terminated after 20 seconds.
    To increase the timeout in the \uicontrol {GDB timeout} field, select
    \preferences > \uicontrol Debugger >
    \uicontrol GDB. For more information about settings that you can specify
    to manage the GDB process, see \l{Specifying GDB Settings}.

    For more information about connecting with \c {target extended-remote} mode
    in GDB, see \l{https://sourceware.org/gdb/onlinedocs/gdb/Connecting.html}
    {Debugging with GDB: Connecting to a Remote Target}.

    \section1 Using CDB

    In remote mode, the local CDB process talks to a CDB process that runs on
    the remote machine. The process is started with special command-line options
    that switch it into server mode. The remote CDB process must load the \QC
    CDB extension library that is shipped with \QC:

    \list 1

        \li Install the \e{Debugging Tools for Windows} on the remote machine.
            The installation folder has the CDB command-line executable
            (\c cdb.exe).

        \li Copy the \QC CDB extension library and the dependencies from the Qt installation
            directory to a new folder on the remote machine (32 or 64 bit
            version depending on the version of the Debugging Tools for Windows
            used):

        \list

            \li \c {\lib\qtcreatorcdbext32} (32 bit)

            \li \c {\lib\qtcreatorcdbext64} (64 bit)

        \endlist

        \li Set the _NT_DEBUGGER_EXTENSION_PATH environment variable to point
            to that folder.

        \li To use TCP/IP as communication protocol, launch remote CDB as
            follows:

            \code
            cdb.exe -server tcp:port=1234 <executable>
            \endcode

        \li On the local machine running \QC, select
            \uicontrol Debug > \uicontrol {Start Debugging} >
            \uicontrol {Attach to Remote CDB Session}.


        \li In the \uicontrol Connection field enter the connection parameters.
            For example, for TCP/IP:

            \code
            Server:Port
            \endcode

            If you chose some other protocol, specify one of the alternative
            formats:

            \code
            tcp:server=Server,port=Port[,password=Password][,ipversion=6]
            tcp:clicon=Server,port=Port[,password=Password][,ipversion=6]
            npipe:server=Server,pipe=PipeName[,password=Password]
            com:port=COMPort,baud=BaudRate,channel=COMChannel[,password=Password]
            spipe:proto=Protocol,{certuser=Cert|machuser=Cert},server=Server,pipe=PipeName[,password=Password]
            ssl:proto=Protocol,{certuser=Cert|machuser=Cert},server=Server,port=Socket[,password=Password]
            ssl:proto=Protocol,{certuser=Cert|machuser=Cert},clicon=Server,port=Socket[,password=Password]
            \endcode

            \li  Click \uicontrol OK to start debugging.

    \endlist

    To specify settings for managing the CDB process, select \preferences >
    \uicontrol Debugger > \uicontrol CDB. For more information, see
    \l{Specifying CDB Settings}.
*/


/*!
    \page creator-debug-mode.html
    \if defined(qtdesignstudio)
    \previouspage studio-debugging.html
    \else
    \previouspage creator-debugger-operating-modes.html
    \endif
    \nextpage creator-stack-view.html

    \title Debug Mode Views

    In the \uicontrol Debug mode, you can inspect the state of your
    application while debugging.

    \image qtcreator-debugger-views.webp {Debug mode views while debugging}

    You can interact with the debugger in many ways:

    \list

        \li Interrupt running applications.

        \li Set breakpoints.

        \li Step through an application line-by-line or
            instruction-by-instruction.

        \li Examine the contents of the call stack.

        \li Examine and modify contents of local and global variables.

        \li Examine and modify registers and memory contents of
            the debugged application.

        \li Examine the list of loaded shared libraries.

        \li Disassemble sections of code.
    \endlist

    The following table summarizes the \uicontrol Debug mode views with links to
    more information.

    \table
    \header
        \li View
        \li Purpose
        \li Learn More
    \row
        \li Stack
        \li Examine the nested function calls leading to the current position
            as a call stack trace.
        \li \l {Viewing Call Stack Trace}
    \row
        \li Breakpoint Preset

            Breakpoints
        \li Set \e {breakpoints} with conditions to make the application stop in
            a controlled way. A \e {watchpoint} stops the application when the
            value of an expression changes.
        \li \l {Setting Breakpoints}
    \row
        \li Threads
        \li Switch between threads.
        \li \l {Viewing Threads}
    \row
        \li Modules
        \li View information about modules included in the application.
        \li \l {Viewing Modules}
    \row
        \li Source Files
        \li View a list of source files included in the project.
        \li \l {Viewing Source Files}
    \row
        \li Locals
        \li View information about the parameters of the function in the topmost
            stack frame and local variables.
        \li \l {Local Variables and Function Parameters}
    \row
        \li Expressions
        \li Compute values of arithmetic expressions or function calls.
        \li \l {Evaluating Expressions}
    \row
        \li Registers
        \li View the current state of the CPU registers to examine the
            application at the machine level.
        \li \l {Viewing and Editing Register State}
    \row
        \li Peripheral Registers
        \li View the current state of peripheral registers.
        \li \l {Peripheral Registers}
    \row
        \li Global Debugger Log

            Debugger Log
        \li View debug output to find out why the debugger does not work.

            The log view acts as a console, so you can send the contents
            of the line under the text cursor in the log directly to the
            native debugger.
        \li \l{Troubleshooting Debugger}

            \l {Debugger Log}
     \row
        \li Disassembler
        \li View disassembled code for the current function.
        \li \l {Viewing Disassembled Code}
     \row
        \li Editor
        \li Open the current source file in the text editor for changing it.
        \li \l {Edit Mode}
    \endtable

    \note The \uicontrol Views menu shows some views only while you are
    debugging.

    \section1 Managing Debug Views

    When you are not debugging, the \uicontrol Debug mode shows the
    \uicontrol {Debugger Preset} perspective:

    \image qtcreator-debugger-views-initial.webp {Initial Debug mode views}

    During debugging, the mode shows the views that you usually need to
    debug C++ or QML applications. To show other views or to hide views,
    select \uicontrol Views.

    You can drag the views in \QC to new positions on the screen. \QC saves the
    size and position of views as a perspective for future sessions. Select
    \uicontrol View > \uicontrol Views > \uicontrol {Reset to Default Layout}
    to reset the views to their original sizes and positions.

    To show and hide columns in views, toggle \uicontrol {Show Column} in
    the context menu.

    \section1 Customizing Debug Views

    To change the appearance and behavior of the debug views, set preferences
    in \preferences > \uicontrol Debugger > \uicontrol General.

    \image qtcreator-debugger-general-options.png {General tab in Debugger preferences}

    For example, you can:

    \list
        \li Use alternating row colors in debug views.
        \li Adopt font size changes from the main editor.
        \li Show tooltips in the main editor while you are debugging.
        \li Close temporary source and memory views and switch to the previously
            used \QC mode when the debugger exits.
        \li Bring \QC to the foreground when the debugged application is
            interrupted.
    \endlist

    For more information, see \l{Debugger Preferences}.
*/

/*!
    \page creator-debugger-stopping.html
    \previouspage creator-disassembler-view.html
    \nextpage creator-debugger-examining-data.html

    \title Stopping Applications

    Once the application starts running under the control of the debugger, it
    behaves and performs as usual.

    To interrupt a running C++ application, select \uicontrol Debug >
    \uicontrol Interrupt. The debugger automatically interrupts
    the application when it hits a \l {Setting Breakpoints}{breakpoint}.

    Once the application stops, \QC:

    \list

        \li Retrieves data representing the \l{Viewing Call Stack Trace}
            {call stack} at the application's current position.

        \li Retrieves the contents of \l{Local Variables and Function Parameters}
            {local variables}.

        \li Examines \l{Evaluating Expressions}{expressions}.

        \li Updates the \l{Viewing and Editing Register State}{Registers},
            \l{Viewing Modules}{Modules}, and \l{Viewing Disassembled Code}
            {Disassembler} views if you are debugging C++ based applications.

    \endlist
    You can \l{Examining Data}{Examine} and change variables, set or remove
    breakpoints, and then continue running the application.
*/

/*!
    \page creator-debugger-examining-data.html
    \previouspage creator-debugger-stopping.html
    \nextpage creator-remote-debugging.html

    \title Examining Data

    When the application stops, you can examine certain data in the debugger. The
    availability of data depends on the compiler settings when compiling the
    application and the exact location where the application stops.

    Unexpected events are called \e exceptions and the debugger can stop
    the application when they occur. Going to the location in the code where
    the exception occurred helps you investigate the problem and find ways to
    fix it.

    If you have a variable that shows text, but the application does not display
    it correctly, for example, your data might be incorrect or the code that sets
    the display text might do something wrong. You can step through the code and
    examine changes to the variable to find out where the error occurs.

    The following video shows how to examine variable values:

    \youtube EhJ1eV_6RH8

    \section1 Showing Tooltips for Simple Values

    To display the value of a simple variable, hover the mouse pointer over its
    name in the code editor.

    \image qtcreator-debugger-value-tooltips.webp {Value tooltip in code editor}

    To keep the tooltip visible, click the pin button.
    You can expand pinned tooltips to view their full content.

    Pinned tooltips are stored in the session. To close all pinned tooltips,
    select \uicontrol {Close Editor Tooltips} in the context menu in the
    \uicontrol Locals or \uicontrol Expressions view.

    To disable tooltips for performance reasons, select \preferences >
    \uicontrol Debugger > \uicontrol General >
    \uicontrol {Use tooltips in main editor when debugging}.

    \section1 Examining Complex Values in Debug Views

    \QC displays the raw information from the native debuggers in a clear and
    concise manner to simplify the debugging process without losing the power
    of the native debuggers.

    \image qtcreator-locals.png {Locals view}

    The \l {Local Variables and Function Parameters}{Locals} and
    \l {Evaluating Expressions}{Expressions} views show structured
    data, such as objects of \c class, \c struct, or \c union types, as a tree.
    To access sub-structures of the objects, expand the tree nodes.
    The tree shows the sub-structures in their in-memory order. To show them
    in alphabetic order, select \uicontrol {Sort Members of Classes and Structs
    Alphabetically} in the context menu.

    Similarly, pointers are displayed as a tree item with a single
    child item representing the target of the pointer. Select
    \uicontrol {Dereference Pointers Automatically} in the context
    menu to combine the pointer and the target into a single entry that
    shows the name and the type of the pointer and the value of the target.

    The standard representation is good enough for the examination of simple
    structures, but it does usually not give enough insight into more complex
    structures, such as \c QObjects or associative containers. These items are
    internally represented by a complex arrangement of pointers, often highly
    optimized, with part of the data not directly accessible through neither
    sub-structures nor pointers.

    To show complex structures, such as \c QObjects or associative containers,
    in a clear and concise manner, \QC uses Python scripts that are called
    \l{Using Debugging Helpers}{debugging helpers}.

    In addition to the generic IDE functionality of the
    \l {Viewing Call Stack Trace}{Stack}, \uicontrol {Locals},
    \uicontrol {Expressions}, \l {Viewing and Editing Register State}{Registers},
    and other views, \QC makes debugging Qt-based applications easy. The debugger
    plugin understands the internal layout of several Qt classes, for example,
    QString, the Qt containers, and most importantly QObject (and classes derived
    from it), as well as most containers of the C++ Standard Library and some GCC
    extensions. It uses this deeper understanding to present objects of such
    classes in a useful way.

    To change the number of array elements that are
    requested when expanding entries, select \preferences > \uicontrol {Debugger}
    > \uicontrol {Locals & Expressions} > \uicontrol {Default array size}.

    \section1 Stepping Through Code

    The following table summarizes the functions that you can use to step through
    the code and examine the changes in variables.

    \table
        \header
            \li Button
            \li Function
            \li Keyboard Shortcut
            \li Description
        \row
            \li \inlineimage icons/qtcreator-debug-button-stop.png
            \li \uicontrol {Stop Debugger}
            \li \key {Shift+F5}
            \li Stops the debugger.
        \row
            \li \inlineimage icons/debugger_stepover_small.png
            \li \uicontrol {Step Over}
            \li \key F10 (\key {Command+Shift+O} on \macos)
            \li Steps over the next line inside the function being debugged. It
                executes the call and moves to the next line to be executed in
                the function.
        \row
            \li \inlineimage icons/debugger_stepinto_small.png
            \li \uicontrol {Step Into}
            \li \key F11 (\key {Command+Shift+I} on \macos)
            \li Steps into the line that it is currently on. For a function call,
                goes into the function and is ready to continue.
        \row
            \li \inlineimage icons/debugger_stepout_small.png
            \li \uicontrol {Step Out}
            \li \key {Shift+F11} (\key {Command+Shift+T} on \macos)
            \li Finishes executing the function and exits to the function that
                it was called from.
        \row
            \li
            \li \uicontrol {Run to Line}
            \li \key {Ctrl+F10} (\key {Shift+F8} on \macos)
            \li Runs to the line that has the cursor.

                You can also directly jump to a line instead of executing until
                the end of the line, to avoid a variable getting modified or a
                function getting called, for example.
        \row
            \li
            \li \uicontrol {Run to Selected Function}
            \li \key {Ctrl+F6}
            \li Runs to the selected function when you are stepping into a nested
                function.
        \row
            \li \inlineimage icons/qtcreator-debugging-continue.png
            \li \uicontrol {Continue}
            \li \key F5
            \li Resumes application execution at the address where it last
                stopped.
    \endtable

    \section2 Compressing Steps in GDB

    When using GDB as the debugging backend, you can compress several steps
    into one step for less noisy debugging. For more information, see
    \l{Specifying GDB Settings}.

    The extended GDB settings have the option to step backwards in code,
    but this option should be used with care, as it is slow and unstable on the
    GDB side. For more information, see \l{Specifying GDB Settings}.

    \section2 Stepping into Frameworks in \macos

    In \macos, external libraries are usually built into so-called Frameworks,
    which may have both release and debug versions of the library. When you
    run applications on the \macos desktop, the release version of Frameworks is
    used by default. To step into Frameworks, select the
    \uicontrol {Use debug versions of Frameworks} option in the project run
    settings.

    \section1 Inspecting Basic Qt Objects

    The most powerful feature of the debugger is that the \uicontrol {Locals}
    and \uicontrol {Expressions} views show the data that belongs to
    Qt's basic objects. For example, in case of QObject, instead of
    a pointer to some private data structure, you see a list of
    children, signals, and slots.

    Similarly, instead of displaying many pointers and integers, \QC's debugger
    displays the contents of a QHash or QMap in an orderly manner. Also, the
    debugger shows access data for QFileInfo and the \e real contents of QVariant.

    \section2 Changing Value Display format

    In the \uicontrol {Locals} or the \uicontrol {Expressions} view, select
    \uicontrol {Change Value Display Format} in the context menu to change the
    value display format. The available options depend on the type of the
    current items, and are provided by the debugging helpers.

    To force a plain C-like display of structures, select \preferences >
    \uicontrol Debugger > \uicontrol {Locals & Expressions}, and then deselect the
    \uicontrol {Use Debugging Helpers} check box. This still uses the
    Python scripts, but generates more basic output. To force the plain display
    for a single object or for all objects of a given type, select
    \uicontrol {Change Value Display Format} > \uicontrol Raw in the context
    menu of the \uicontrol Locals or \uicontrol Expressions view.

    Typically, you can change the encoding for string-like data, such as
    \c{QByteArray} and \c{std::string}, or show the data in a full editor
    window.

    You can select a \e compact option for map-like data, such as \c{QMap},
    \c{QHash}, and \c{std::map}, that uses the \uicontrol {Name} column for
    keys and results in a concise display of containers with short keys,
    such as numbers or short strings. For example, to expand all the values
    of QMap, select \uicontrol {Change Value Display Format} > \uicontrol Compact.

    For strings, you can select \uicontrol {Change Value Display Format} >
    \uicontrol {Separate Window} to see string content inside a text edit
    instead of a single line item in the view. For QPixmap, you can see
    the pixmap being created pixel-by-pixel when stepping through the code.

    \section2 Changing Variable Values

    You can use the \uicontrol {Locals} and \uicontrol {Expressions} view to change
    the contents of variables of simple data types, for example, \c int, \c float,
    \c QString and \c std::string when the application is interrupted. To do so,
    click the \uicontrol Value column, modify the value with the inplace editor,
    and press \key Enter.

    To change the complete contents of QVector or \c std::vector values, type
    all values separated by commas into the \uicontrol Value column of the main
    entry. However, \QC does not try to reallocate memory for variables, so it
    applies the changes only if the new content fits into the old memory and if
    the debugger supports changing values.

    \section2 Signal-Slot Connections

    If an instance of a class is derived from QObject, you can find all other
    objects connected to this object's slots with Qt's signals and slots
    mechanism. Select \preferences > \uicontrol {Debugger} >
    \uicontrol {Locals & Expressions} > \uicontrol {Use Debugging Helpers}.

    \image qtcreator-debugging-helper-options.webp {Locals & Expressions preferences}

    In the \uicontrol Locals view, expand the object's entry and open the slot
    in the \e slots subitem. The view shows the objects connected to this slot
    as children of the slot. Similarly, you can show the children of signals.

    \section2 Low-level Data

    If you cannot debug Qt objects because their data is corrupted, you can
    switch off the debugging helpers to make low-level structures visible.

    To switch off the debugging helpers, deselect
    \uicontrol {Use Debugging Helpers} in \preferences >
    \uicontrol Debugger > \uicontrol {Locals & Expressions}.

    \omit
    \section2 Creating Snapshots

    A snapshot has the complete state of the debugged application at a time,
    including the full memory contents.

    To create snapshots of a debugged application, select \uicontrol {Create Snapshot}
    in the context menu in the \uicontrol {Debugger Perspectives} view.

    Double-click on entries in the \uicontrol {Debugger Perspectives} view to
    switch between snapshots. The debug mode views are updated to reflect the state
    of the application at time of taking the snapshot.

    \note Creating snapshots involves creating core files of the debugged process,
    requiring significant amount of disk space. For details, see
    \l{https://sourceware.org/gdb/onlinedocs/gdb/Core-File-Generation.html}.

    \endomit
*/

/*!
    \page creator-threads-view.html
    \previouspage creator-breakpoints-view.html
    \nextpage creator-modules-view.html

    \title Viewing Threads

    An application can have more than one thread of execution that share one
    address space, which means that they can examine and change the same
    variables. However, each thread has its own registers, execution stack,
    and possibly private memory.

    When a multi-threaded application is interrupted, you can view the threads
    currently active in the application and switch between them in the
    \uicontrol Threads view (1):

    \image qtcreator-debugger-threads.webp {Threads view}

    You can also select a thread in the \uicontrol Threads field (2) on the
    debugger toolbar.

    This allows you to select the thread that is in the focus of the debugger.

    The \l {Viewing Call Stack Trace}{Stack} view adjusts its contents
    accordingly.
*/

/*!
    \page creator-modules-view.html
    \previouspage creator-threads-view.html
    \nextpage creator-source-files-view.html

    \title Viewing Modules

    The \uicontrol Modules view displays information that the debugger plugin
    has about modules included in the application that is being debugged.

    A module is:

    \list
        \li A dynamic link library (\c {.dll}) in Windows
        \li A shared object (\c {.so}) in Linux
        \li A dynamic shared library (\c {.dylib}) in \macos
    \endlist

    \image qtcreator-debugger-modules.webp {Modules view}

    In addition, the view displays symbols within the modules and indicates
    where each module was loaded. Right-click column headers to show and
    hide columns in the view.

    Right-click the view to select the following actions:

    \list

        \li Update the module list

        \li Show source files for a module

        \li Show dependencies between modules (Windows only)

        \li Load symbols for modules

        \li Examine modules

        \li Edit module files

        \li Show symbols in modules

        \li Show sections in modules

        \li Set \l{Debugger Preferences}{debugger preferences}

    \endlist

    By default, the \uicontrol Modules view is hidden. To show it, select it in
    \uicontrol Views on the debugger toolbar.

    \section1 Breaking on Loading Modules in CDB

    When using CDB as debug backend, you can specify that the debugger should
    break when application modules are loaded or unloaded. To enable breaking
    for the specified modules, select \preferences > \uicontrol Debugger >
    \uicontrol CDB.

    \image qtcreator-cdb-options.png {CDB tab in Debugger preferences}

    For more information, see \l{Specifying CDB Settings}.
*/

/*!
    \page creator-source-files-view.html
    \previouspage creator-modules-view.html
    \nextpage creator-locals-view.html

    \title Viewing Source Files

    The \uicontrol {Source Files} view lists all the source files included in
    the project. If you cannot step into an instruction, you can check whether
    the source file is actually part of the project, or whether it was compiled
    elsewhere. The view shows the path to each file in the file system.

    \image qtcreator-debugger-source-files.webp {Source Files view}

    Right-click the view to select the following actions:

    \list
        \li Reload data
        \li Open the selected file
        \li Set \l{Debugger Preferences}{debugger preferences}
    \endlist

    By default, the \uicontrol {Source Files} view is hidden. To show it, select
    it in \uicontrol Views on the debugger toolbar.

    \section1 External Sources

    To enable the debugger to step into the code and display the source code
    when using a copy of the source tree at a location different from the one
    at which the libraries were built, you can map source paths to target
    paths in \preferences > \uicontrol Debugger > \uicontrol General:

    \image qtcreator-debugger-general-options.png {General tab in Debugger preferences}

    For more information, see \l{Mapping Source Paths}.
*/

/*!
    \page creator-registers-view.html
    \previouspage creator-expressions-view.html
    \nextpage creator-peripheral-registers-view.html

    \title Viewing and Editing Register State

    \e {Machine code} consists of machine language instructions that make the CPU
    perform tasks, such as load or store, on units of data in the CPU's registers
    or memory.

    The \uicontrol Registers view displays the current state of general-purpose
    and special-purpose CPU registers. The available registers depend on the CPU
    type.

    \image qtcreator-debugger-registers-view.webp {Registers view}

    You can view register values when the application stops. Double-click
    register values to edit them.

    The values of registers that recently changed are highlighted in red. Empty
    register values and leading zeroes are grayed out.

    Right-click column headers to show and hide the \uicontrol Name and
    \uicontrol Value columns in the view.

    Right-click the view to select the following actions:

    \list
        \li Reload register list.
        \li Open \l {Examining Memory}{Memory Editor} at the selected value.
        \li Open the \l {Viewing Disassembled Code}{Disassembler} view.
        \li Display a value in hexadecimal, decimal, octal, or binary format.
        \li Set \l{Debugger Preferences}{debugger preferences}.
    \endlist

    By default, the \uicontrol Registers view is hidden. To show it, select it in
    \uicontrol Views on the debugger toolbar.

    \section1 Examining Memory

    You can examine memory in many formats, independently of the application's
    data types.

    To open the memory editor, select a value \uicontrol Registers view,
    and then select \uicontrol {Open Memory Editor at <value>} or
    \uicontrol {Open Memory View at <value>} in the context menu:

    \image qtcreator-debugger-memory-editor.webp {Memory Editor}

    Hover the mouse pointer on a value to see details as a tooltip.

    Right-click a value to:

    \list
        \li Copy the selection in ASCII or hexadecimal format.
        \li Set a data breakpoint on the selection.
        \li Jump to the selected address in the current data view or a new one.
    \endlist
*/

/*!
    \page creator-peripheral-registers-view.html
    \previouspage creator-registers-view.html
    \nextpage creator-debugger-log-view.html

    \title Peripheral Registers

    The \uicontrol {Peripheral Registers} view displays the current state of
    peripheral devices, such as a mouse, keyboard, display, printer, or USB
    drive. Applications write registers to send information to the device and
    read them to get information from the device. To read registers in a
    peripheral device, the application accesses its I/O addresses with a load
    or store instruction that the CPU issues.

    \image qtcreator-debugger-peripheral-registers-view.webp {Peripheral Registers view}

    The \uicontrol Access column shows whether the register is read-and-write
    (\uicontrol RW), read-only (\uicontrol RO), or write-only (\uicontrol WO).
    \uicontrol N/A means that the access type is not available.

    Right-click column headers to show and hide columns in the view.

    Right-click the view to select the following actions:

    \list
        \li View register groups.
        \li Set \l{Debugger Preferences}{debugger preferences}.
    \endlist

    By default, the \uicontrol {Peripheral Registers} view is hidden. To show it,
    select it in \uicontrol Views on the debugger toolbar.
*/

/*!
    \page creator-debugger-log-view.html
    \previouspage creator-peripheral-registers-view.html
    \nextpage creator-disassembler-view.html

    \title Debugger Log

    You can view debug output in the \uicontrol {Debugger Log} view to
    \l {Debugger Does Not Work}{troubleshoot the debugger}.

    \image qtcreator-debugger-log-view.webp {Debugger Log view}

    If debug output is sent to the system log, select \preferences >
    \uicontrol Debugger > \uicontrol General >
    \uicontrol {Force logging to console} check box.

    Right-click the view to select the following actions:

    \list
        \li Copy, paste, cut, and delete log contents.
        \li Undo and redo editing actions.
        \li Select all log contents.
        \li Clear log contents.
        \li Save log contents as a file.
        \li Log time stamps.
        \li Reload debugging helpers after \l{Adding Custom Debugging Helpers}
            {adding custom debugging helpers}.
        \li Set \l{Debugger Preferences}{debugger preferences}.
    \endlist

    \section1 Directly Interacting with Native Debuggers

    You can use the left pane of the \uicontrol {Debugger Log} view to directly
    interact with the command line of the native debugger.

    Press \key {Ctrl+Enter} to send the contents of the line under the
    text cursor to the native debugger. Or, enter the command in the
    \uicontrol Command field. The right side pane of the
    \uicontrol {Debugger Log} view shows the command output.

    \note Usually, you do not need this feature because \QC offers better ways to
    handle the task. For example, instead of using the GDB
    \c print command from the command line, you can evaluate an expression in
    the \l {Evaluating Expressions}{Expressions} view.
*/

/*!
    \page creator-disassembler-view.html
    \previouspage creator-debugger-log-view.html
    \nextpage creator-debugger-stopping.html

    \title Viewing Disassembled Code

    A \e disassembler translates machine language into assembly language for
    human-readability.

    The \uicontrol Disassembler view displays disassembled code for the current
    function. It is useful for low-level commands for checking single
    instructions, such as \uicontrol {Step Into} and \uicontrol {Step Over}.

    \image qtcreator-debugger-disassembler-view.webp {Disassembler view}

    By default, GDB shows AT&T style disassembly. To switch to the Intel style,
    select \preferences > \uicontrol Debugger >
    \uicontrol GDB > \uicontrol {Use Intel style disassembly}.

    To open the \uicontrol Disassembler view:

    \list
        \li Select \uicontrol Debug > \uicontrol {Operate by Instruction} while
            the debugger is running.
        \li Select the \inlineimage icons/debugger_singleinstructionmode.png
            (\uicontrol {Operate by Instruction}) tool button on the debugger
            toolbar.
        \li In the \l {Viewing and Editing Register State}{Registers} view,
            select a value, and then select \uicontrol {Open Disassembler at <value>}
            in the context menu.
    \endlist

    \section1 Starting Disassembler

    To start a disassembler from the \uicontrol Registers view, select
    \uicontrol {Open Disassembler} and  set the disassembler address:

    \image qcreator-debugger-select-start-address.webp {Select Start Address dialog}
*/

/*!
    \previouspage creator-debugger-preferences.html
    \page creator-debugging-helpers.html
    \nextpage creator-debugging-qml.html

    \title Using Debugging Helpers

    To show complex structures, such as \c QObjects or associative containers,
    in a clear and concise manner, \QC uses Python scripts that are called
    \e {debugging helpers}.

    \QC ships with debugging helpers for more than 200 of the most popular Qt
    classes, standard C++ containers, and smart pointers, covering the usual
    needs of a C++ application developer out-of-the-box.

    \section1 Extending Debugging Helpers

    \QC uses Python scripts to translate raw memory contents and type information
    data from native debugger backends (GDB, LLDB, and CDB are currently supported)
    into the form presented to the user in the
    \l {Local Variables and Function Parameters}{Locals}
    and \l {Evaluating Expressions}{Expressions} views.

    Unlike GDB's
    \l{https://sourceware.org/gdb/onlinedocs/gdb/Pretty-Printing.html#Pretty-Printing}
    {pretty printers} and LLDB's \l{http://lldb.llvm.org/varformats.html}
    {data formatters}, \QC's debugging helpers are independent of the
    native debugging backend. That is, the same code can be used with GDB on
    Linux, LLDB on macOS, and CDB on Windows, or any other platform on which at
    least one of the three supported backends is available.

    To use the default GDB pretty printers installed in your system or linked
    to the libraries your application uses, select \preferences >
    \uicontrol Debugger > \uicontrol GDB > \uicontrol {Load system GDB pretty
    printers}. For more information, see \l{Specifying GDB Settings}.

    \image qtcreator-preferences-debugger-gdb.webp {GDB preferences}

    \section2 Customizing Built-In Debugging Helpers

    You can have commands executed after built-in debugging helpers have
    been loaded and fully initialized. To load additional debugging helpers or
    modify existing ones, select \preferences > \uicontrol Debugger >
    \uicontrol {Locals & Expressions}, and enter the commands in the
    \uicontrol {Debugging Helper Customization} field.

    \image qtcreator-debugging-helper-options.webp {Locals & Expressions preferences}

    If you receive error messages about receiving signals when using GDB, you
    can specify \l{https://sourceware.org/gdb/onlinedocs/gdb/Signals.html}
    {GDB commands} for handling the signals. For example, you can tell GDB to
    ignore the \c SIGSTOP signal if you receive the following error message:
    \c {The inferior stopped because it received a signal from the operating
    system. Signal name: SIGSTOP}.

    To stop GDB from handling the \c SIGSTOP signal, add the following commands
    to the \uicontrol {Debugging Helper Customization} field:

    \badcode
    handle SIGSTOP nopass
    handle SIGSTOP nostop
    \endcode

    To display a message box as soon as your application receives a signal
    during debugging, select \preferences > \uicontrol Debugger > \uicontrol GDB >
    \uicontrol {Show a message box when receiving a signal}.

    \section2 Adding Custom Debugging Helpers

    To add debugging helpers for your own types, no compilation is required,
    just adding a few lines of Python. The scripts can address multiple versions
    of Qt, or of your own library, at the same time.

    To add debugging helpers for custom types, add debugging helper
    implementations to the startup file of the native debuggers (for example,
    \c{~/.gdbinit} or \c{~/.lldbinit}) or specify them directly in the
    \uicontrol {Additional Startup Commands} in \preferences >
    \uicontrol Debugger > \uicontrol GDB.

    To get started with implementing debugging helpers for your own data types,
    you can put their implementation into the file
    \c share/qtcreator/debugger/personaltypes.py in your Qt installation or
    stand-alone \QC installation. On \macos, the file is bundled into the
    \QC application package, where it is located in the
    \c Contents/resources/debugger folder.

    The \c personaltypes.py file has one example implementation:

    \quotefromfile ../../../share/qtcreator/debugger/personaltypes.py
    \skipto qdump__
    \printuntil d.putItem

    To add debugging helpers:

    \list 1

        \li Open the \c share/qtcreator/debugger/personaltypes.py file for
            editing. For example, if your Qt installation is located in the
            \c Qt5 directory on Windows, look in
            \c C:\Qt5\Tools\QtCreator\share\qtcreator\debugger. On \macos, look
            in \c {Qt5/Qt Creator.app/Contents/resources/debugger}.

        \li Add your dumper implementation to the end of the \c personaltypes.py
            file.  For more information about implementing debugging helpers,
            see the following sections.

        \li To prevent \c personaltypes.py from being overwritten when you
            update your \QC installation (when updating your Qt installation,
            for example), copy it to a safe location outside the \QC
            installation in your file system and specify the location in
            \preferences > \uicontrol Debugger > \uicontrol {Locals & Expressions}
            > \uicontrol {Extra Debugging Helper}.
    \endlist

    The custom debugging helpers will be automatically picked up from
    \c personaltypes.py when you start a debugging session in \QC or select
    \uicontrol {Reload Debugging Helpers} from the context menu of the
    \l {Debugger Log} view.

    \section2 Debugging Helper Overview

    The implementation of a debugging helper typically consists of a single
    Python function, which needs to be named \c{qdump__NS__Foo}, where
    \c{NS::Foo} is the class or class template to be examined. Note that the
    \c{::} scope resolution operator is replaced by double underscores: \c{__}.
    Nested namespaces are possible. Template arguments are not used for
    the construction of the function name.

    Examples:

    \list

        \li The name for the function implementing a debugging helper for the type
            \c{namespace Project { template<typename T> struct Foo {... } } } is
            \c{qdump__Project__Foo}.

        \li The name for the function implementing a debugging helper
            for the type \c{std::__1::vector<T>::iterator} is
            \c{qdump__std____1__vector__iterator}.

    \endlist


    \QC's debugger plugin calls this function whenever you want to display an
    object of this type. The function is passed the following parameters:

    \list

        \li \c d of type \c Dumper, an object that has the current settings and
            providing facilities to build up an object representing a part of
            the \uicontrol Locals and \uicontrol Expressions views.

        \li \c value of type \c Value, wrapping either a
            \l{https://sourceware.org/gdb/onlinedocs/gdb/Values-From-Inferior.html}
            {gdb.Value} or an
            \l{https://lldb.llvm.org/cpp_reference/classlldb_1_1SBValue.html}
            {lldb.SBValue}.

    \endlist

    The \c{qdump__*} function has to feed the Dumper object with certain
    information that is used to build up the object and its children's display
    in the \uicontrol Locals and \uicontrol Expressions views.

    Example:

    \code
    def qdump__QFiniteStack(d, value):
        alloc = value["_alloc"].integer()
        size = value["_size"].integer()
        d.putItemCount(size)
        if d.isExpanded():
            d.putArrayData(value["_array"], size, value.type[0])
    \endcode

    \note To create dumper functions usable with both LLDB and GDB backends,
    avoid direct access to the \c gdb.* and \c lldb.* namespaces and use the
    functions of the \c Dumper class instead.

    To get to the base instance of the object in the debugging helper, use the
    \c value.base() function or the following example code:

    \code
    def qdump__A(d, value):
       t = value.members(True)[0].type
       dptr, base_v = value.split('p{%s}' % t.name)
       d.putItem(base_v)
    \endcode

    Debugging helpers can be set up to be called whenever a type name matches
    a regular expression. To do so, the debugging helper's function name must
    begin with \c{qdump__} (with two underscore characters). In addition,
    the function needs to have a third parameter called \c regex with a default
    value that specifies the regular expression that the type name should match.

    For example, the Nim 0.12 compiler assigns artificial names, such as \c{TY1}
    and \c{TY2}, to all generic sequences it compiles. To visualize these in
    \QC, the following debugging helper may be used:

    \code
    def qdump__NimGenericSequence__(d, value, regex = "^TY.*$"):
        size = value["Sup"]["len"]
        base = value["data"].dereference()
        typeobj = base.dereference().type
        d.putArrayData(base, size, typeobj)
    \endcode

    \section2 Debugging Helper Implementation

    A debugging helper creates a description of the displayed data item
    in a format that is similar to GDB/MI and JSON.

    For each line in the \uicontrol Locals and \uicontrol Expressions views, a
    string like the following needs to be created and channeled to the debugger
    plugin.

    \code
    { iname='some internal name',           # optional
      address='object address in memory',   # optional
      name='contents of the name column',   # optional
      value='contents of the value column',
      type='contents of the type column',
      numchild='number of children',        # zero/nonzero is sufficient
      children=[              # only needed if item is expanded in view
         {iname='internal name of first child',
           },
         {iname='internal name of second child',
           },

      ]}
    \endcode

    The value of the \c iname field is the internal name of the object,
    which consists of a dot-separated list of identifiers, corresponding to the
    position of the object's representation in the view. If it is not present,
    it is generated by concatenating the parent object's \c iname, a dot, and a
    sequential number.

    The value of the \c name field is displayed in the \uicontrol Name column
    of the view. If it is not specified, a simple number in brackets is used
    instead.

    As the format is not guaranteed to be stable, it is strongly recommended
    not to generate the wire format directly, but to use the abstraction
    layer of the Python Dumper classes, specifically the \c{Dumper}
    class itself, and the \c{Dumper:Value} and \c{Dumper:Type} abstractions.
    These offer a complete framework to take care of the \c iname and \c addr
    fields, to handle children of simple types, references, pointers, enums, and
    known and unknown structs, as well as some convenience functions to handle
    common situations.

    When using CDB as debugger backend, you can enable the Python dumper by
    selecting \preferences > \uicontrol Debugger >
    \uicontrol CDB > \uicontrol {Use Python dumper}.

    \image qtcreator-cdb-options.png {CDB preferences}

    The following sections describe some of the widely-used Dumper classes and
    members specified in \c qtcreator\share\qtcreator\debugger\dumper.py.


    \section3 Dumper Class

    The \c Dumper class has generic bookkeeping, low-level, and convenience
    functions:

    \list
        \li \c{putItem(self, value)} - The \e {master function} that handles
            basic types, references, pointers, and enums directly, iterates over
            base classes and class members of compound types, and calls
            \c qdump__* functions when appropriate.

        \li \c{putIntItem(self, name, value)} - Equivalent to:
            \code
            with SubItem(self, name):
                self.putValue(value)
                self.putType("int")
            \endcode

        \li \c{putBoolItem(self, name, value)} - Equivalent to:
            \code
            with SubItem(self, name):
                self.putValue(value)
                self.putType("bool")
            \endcode

        \li \c{putCallItem(self, name, rettype, value, func, *args)} - Uses the
            native debugger backend to place the function call \c func returning
            \c rettype  on the value specified by \a {value} and to output the
            resulting item.

            Native calls are extremely powerful and can leverage existing
            debugging or logging facilities in the debugged process, for
            example. However, they should only be used in a controlled
            environment, and only if there is no other way to access the data,
            for the following reasons:

            \list

                \li Direct execution of code is dangerous. It runs native code
                    with the privileges of the debugged process, with the
                    potential to not only corrupt the debugged process, but also
                    to access the disk and network.

                \li Calls cannot be executed when inspecting a core file.

                \li Calls are expensive to set up and execute in the debugger.

            \endlist

        \li \c{putArrayData(self, address, itemCount, type)} - Creates the
            number of children specified by \c itemCount of the type \c type of
            an array-like object located at \c address.

        \li \c{putSubItem(self, component, value)} - Equivalent to:
            \code
            with SubItem(self, component):
                self.putItem(value)
            \endcode

            Exceptions raised by nested function calls are caught and all output
            produced by \c putItem is replaced by the output of:

            \code
            except RuntimeError:
                d.put('value="<invalid>",type="<unknown>",numchild="0",')
            \endcode

        \li \c{put(self, value)} - A low-level function to directly append to
            the output string. That is also the fastest way to append output.

        \li \c{putField(self, name, value)} - Appends a \c{name='value'} field.

        \li \c{childRange(self)} - Returns the range of children specified in
            the current \c Children scope.

        \li \c{putItemCount(self, count)} - Appends the field
            \c {value='<%d items>'} to the output.

        \li \c{putName(self, name)} - Appends the \c {name=''} field.

        \li \c{putType(self, type, priority=0)} - Appends the field \c {type=''},
            unless the \a type coincides with the parent's default child type or
            \c putType was already called for the current item with a higher
            value of \c priority.

        \li \c{putBetterType(self, type)} - Overrides the last recorded \c type.

        \li \c{putExpandable(self)} - Announces the existence of child items
            for the current value. The default are no children.

        \li \c{putNumChild(self, numchild)} - Announces the existence
            (\c numchild > 0) or non-existence of child items for the current
            value.

        \li \c{putValue(self, value, encoding = None)} - Appends the file
            \c {value=''}, optionally followed by the field \c {valueencoding=''}.
            The \c value needs to be convertible to a string entirely consisting
            of alphanumerical values. The \c encoding parameter can be used to
            specify the encoding in case the real value had to be encoded in
            some way to meet the alphanumerical-only requirement. The parameter
            \c{encoding} is either a string of the form \c codec:itemsize:quote
            where \c{codec} is any of \c{latin1}, \c{utf8}, \c{utf16}, \c{ucs4},
            \c{int}, or \c{float}. \c{itemsize} gives the size of the basic
            component of the object if it is not implied by \c codec and
            \c quote specifies whether or not the value should be surrounded by
            quotes in the display.

            Example:

            \code
                # Safe transport of quirky data. Put quotes around the result.
                d.putValue(d.hexencode("ABC\"DEF"), "utf8:1:1")
            \endcode

        \li \c{putStringValue(self, value)} - Encodes a QString and calls
            \c putValue with the correct \c encoding setting.

        \li \c{putByteArrayValue(self, value)} - Encodes a QByteArray and calls
            \c putValue with the correct \c encoding setting.

        \li \c{isExpanded(self)} - Checks whether the current item is expanded in
            the view.

        \li \c{createType(self, pattern, size = None)} - Creates a \c{Dumper.Type}
            object. The exact operation depends on \c pattern.

            \list

            \li If \c pattern matches the name of a well-known type, a
                \c{Dumper.Type} object describing this type is returned.

            \li If \c pattern is the name of a type known to the native backend,
                the returned type describes the native type.

            \li Otherwise, \c pattern is used to construct a type description by
                interpreting a sequence of items describing the field of a
                structure as follows. Field descriptions consist of one or
                more characters as follows:

                \list

                \li \c q - Signed 8-byte integral value
                \li \c Q - Unsigned 8-byte integral value
                \li \c i - Signed 4-byte integral value
                \li \c I - Unsigned 4-byte integral value
                \li \c h - Signed 2-byte integral value
                \li \c H - Unsigned 2-byte integral value
                \li \c b - Signed 1-byte integral value
                \li \c B - Unsigned 1-byte integral value
                \li \c d - 8-byte IEEE 754 floating point value
                \li \c f - 4-byte IEEE 754 floating point value
                \li \c p - A pointer, that is, an unsigned integral value of
                    suitable size according to the target architecture
                \li \c @ - Suitable padding. The size is determined by the
                    preceding and following field and the target architecture
                \li \c <n>s - A blob of <n> bytes, with implied alignment of 1
                \li \c {<typename>} - A blob of suitable size and suitable
                    alignment determined by a \c{Dumper.Type} with the name
                    \c typename

                \endlist

            \endlist

    \endlist

    \section3 Dumper.Type Class

    The \c{Dumper.Type} class describes the type of a piece of data, typically
    a C++ class or struct, a pointer to a struct, or a primitive type, such as
    an integral or floating point type.

    Type objects, that is, instances of the \c{Dumper.Type} class, can be
    created by native debugger backends, usually by evaluating Debug Information
    built into or shipped alongside the debugged binary, or created on-the-fly
    by the debugging helper.

    \QC offers type information on-the-fly for most Qt
    classes, obliterating the need to use \e Debug builds of Qt for the purpose
    of object introspection.

    The \c{Dumper.Type} class has the following widely-used member functions:

    \list

        \li \c{name} - The name of this type as a string, or \c None if the type
            is anonymous.

        \li \c{size(self)} - Returns the size of an object of this type in
            bytes.

        \li \c{bitsize(self)} - Returns the size of an object of this type in
            bits.

        \li \c{alignment(self)} - Returns the required alignment for objects of
            this type in bytes.

        \li \c{deference(self)} - Returns the dereferences type for pointer
            type, \c None otherwise.

        \li \c{pointer(self)} - Returns a pointer type that can be dereferenced
            to this type.

        \li \c{target(self)} - A convenience function that returns the item type
            for array types and the dereferenced type for pointers and
            references.

        \li \c{stripTypedefs(self)} - Returns the underlying type if this type
            is an alias.

        \li \c{templateArgument(self, position, numeric = False)} - Returns the
            template parameter located at \c{position} if this is a templated
            type. If \c numeric is \c True, returns the parameter as an integral
            value.

        \li \c{fields(self)} - Returns a list of \c{Dumper:Fields} describing
            the base classes and data members of this type.

    \endlist


    \section3 Dumper.Field Class

    The \c{Dumper.Field} class describes a base class or a data member of a type
    object:

    \list

        \li \c{isBaseClass} - Distinguishes between base classes and data
            members.

        \li \c{fieldType(self)} - Returns the type of this base class or data
            member.

        \li \c{parentType(self)} - Returns the owning type.

        \li \c{bitsize(self)} - Returns the size of this field in bits.

        \li \c{bitpos(self)} - Returns the offset of this field in the owning
            type in bits.

    \endlist


    \section3 Dumper.Value Class

    The \c{Dumper.Value} class describes a piece of data, such as instances of
    C++ classes or primitive data types. It can also be used to describe
    artificial items that have no direct representation in memory, such as
    file contents, non-contiguous objects, or collections.

    A \c{Dumper.Value} has always an associated \c{Dumper.Type}. The two
    main representations of the value's actual data are:

    \list

        \li Python object following the Python buffer protocol, such as a Python
            \c memoryview, or a \c bytes object. The \c size() should match the
            size of this value's type.

        \li An integral value representing a pointer to the begin of the object
            in the current address space. The size of the object is given by its
            type's \c{size()}.

    \endlist

    Knowledge of the internal representation of a \c{Dumper.Value} is typically
    not required when creating a debugger helper for it.

    The member function and properties of the \c{Dumper.Value} class are the
    following:

    \list

        \li \c{integer(self)} - Returns an interpretation of this value as a
            signed integral value of a suitable size.

        \li \c{pointer(self)} - Returns an interpretation of this value as a
            pointer in the current address space.

        \li \c{members(self, includeBases)} - Returns a list of \c{Dumper.Value}
            objects representing the base objects and data members of this value.

        \li \c{dereference(self)} - For values describing pointers, returns the
            dereferenced value, and \c None otherwise.

        \li \c{cast(self, type)} - Returns a value that has the same data as
            this value, but the type \c type.

        \li \c{address(self)} - Returns the address of this value if it consists
            of a contiguous region in the current address space, and \c None
            otherwise.

        \li \c{data(self)} - Returns the data of this value as a Python \c bytes
            object.

        \li \c{split(self, pattern)} - Returns a list of values created
            according to \c pattern from this value's data. Acceptable patterns
            are the same as for \c{Dumper.createType}.

        \li \c{dynamicTypeName(self)} - Tries to retrieve the name of the
            dynamic type of this value if this is a base class object. Returns
            \c None if that is not possible.

    \endlist

    \section3 Children and SubItem Class

    The attempt to create child items might lead to errors if data is
    uninitialized or corrupted. To gracefully recover in such situations, use
    \c Children and \c SubItem \e{Context Managers} to create the nested items.

    The \c Children constructor \c{__init__(self, dumper, numChild = 1,
    childType = None, childNumChild = None, maxNumChild = None, addrBase = None,
    addrStep = None)} uses one mandatory argument and several optional
    arguments.  The mandatory argument refers to the current \c Dumper object.
    The optional arguments can be used to specify the number \c numChild of
    children, with type \c childType_ and \c childNumChild_ grandchildren each.
    If \c maxNumChild is specified, only that many children are displayed. This
    should be used when dumping container contents that might take overly long
    otherwise. The parameters \c addrBase and \c addrStep can be used to reduce
    the amount of data produced by the child dumpers. Address printing for the
    \e{n}th child item will be suppressed if its address equals with
    \e{addrBase + n * addrStep}.

    Example:
    \code
    if d.isExpanded():
        with Children(d):
            with SubItem(d):
                d.putName("key")
                d.putItem(key)
            with SubItem(d):
                d.putName("value")
                d.putItem(value)
    \endcode

    Note that this can be written more conveniently as:
    \code
    d.putNumChild(2)
    if d.isExpanded():
        with Children(d):
            d.putSubItem("key", key)
            d.putSubItem("value", value)
    \endcode
*/


/*!
    \previouspage creator-qml-debugging-example.html
    \page creator-troubleshooting-debugging.html
    \nextpage creator-analyze-mode.html

    \title Troubleshooting Debugger

    This section lists some typical problems that you might encounter while
    debugging and solutions to them.

    \section1 Cannot Launch Debugger

    Some anti-virus applications do not allow debuggers to retrieve data. For
    example, on Windows, launching the debugger might fail with the following
    message if the Avira AntiVir is installed on the development PC: \e{The
    inferior stopped because it received a signal from the operating system.
    Signal name:? signal meaning: Unknown signal.}

    Some versions of Avira AntiVir Desktop-Products have known issues in
    various development environments, including \QC. To fix the problem,
    Avira instructs you to update to version \c {avipbb.sys 10.0.22.22}. For
    more information, see
    \l{http://www.avira.com/en/support-for-business-knowledgebase-detail/kbid/805}
    {Restricted Usability of IDE/Debuggers since 2010-12-08}.

    On some devices, such as Wacom Tablets, running processes might stop the
    debugger from launching. Stop all running processes and then relaunch the
    debugger.

    \section1 Debugger Does Not Hit Breakpoints

    You might have created a release build that does not have debug
    information. A GNU Compiler Collection (GCC) debug build has the \c {-g}
    option on the compiler command line. Check that this option is present in
    the \l {Compile Output}. If it is not, adjust your build
    settings in the \uicontrol Projects mode.

    \section1 Debugger Does Not Work

    If the debugger does not work properly, try the following:

    \list 1

        \li Make sure you use at least \QC 3.0.1

        \li Select the \inlineimage icons/run_small.png
            (\uicontrol Run) button to verify that the
            \l {Running on Multiple Platforms}{build and run kit selector}
            picked a runnable target and you can run the application.

        \li Make sure the debugger is \l{Setting Up Debugger}{set up properly}.

        \li In the \uicontrol Debug mode, select \uicontrol View >
            \uicontrol Views > \uicontrol {Debugger Log} to open the
            \l {Debugger Log} view. Browse the contents of the pane on
            the right hand side to find out what went wrong. Always attach the
            contents of the pane to debugger-related questions to the \QC
            mailing list (qt-creator@qt-project.org) or paste them to a
            \l{Pasting and Fetching Code Snippets}{code pasting service} before
            asking questions in the IRC (on the #qt-creator channel at Libera.Chat).

            \note Error 135 usually means that a dependent DLL cannot be found.

    \endlist

    \section1 Pointer Variable Members Are Not Displayed Directly

    When you use the \uicontrol Locals and \uicontrol Expressions views to inspect a
    pointer variable and expand the variable tree item, another tree item level
    is displayed. To directly display the members of the pointer variable,
    select \uicontrol {Dereference Pointers Automatically} in the context
    menu in the \uicontrol Locals and \uicontrol Expressions views.

    If you cannot view variables at all, check that you selected a \e debug build
    configuration.

    \section1 Structure Members Are Not Sorted According to Structure Layout

    By default, structure members are displayed in alphabetic order. To inspect
    the real layout in memory, deselect
    \uicontrol {Sort Members of Classes and Structs Alphabetically} in the
    context menu in the \uicontrol Locals and \uicontrol Expressions views.

    \section1 Built-in Debugger Is Slow During Startup and Runtime

    Slowness that is related to the loading of debug information is hard to
    avoid. The following sections describe some possible solutions.

    \section2 Caching GDB Symbol Index

    When using GDB as backend, you can automatically save a copy of
    its symbol index in a cache on disk and retrieve it from there
    when loading the same binary in the future. Select \preferences >
    \uicontrol Debugger > \uicontrol GDB > \uicontrol {Use automatic symbol cache}.

    \image qtcreator-preferences-debugger-gdb.webp {GDB preferences}

    \section2 Minimizing Number of Breakpoints

    Some debugging slowness stems from maintaining breakpoints inside
    the debugger (under some circumstances all breakpoints need to be inserted
    and removed again for each step) and the evaluation of expressions after
    each step. We recommend that you minimize the number of breakpoints and
    watched expressions.

    \section2 Cleaning Builds

    If out-of-date .pdb files make debugging slower, try a clean build.

    \section2 Disabling Incremental Linking

    Incremental linking can affect debugging. If the \l {Debugger Log} view shows
    the \e {Unable to verify checksum of module} message, disable incremental
    linking.

    When using CMake as the build system, add the following line to the project
    CMakeLists.txt file:

    \badcode
    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} /INCREMENTAL:NO" )
    \endcode

    When using qmake as the build system, add the following line to the project
    .pro file:

    \badcode
    QMAKE_LFLAGS_DEBUG += /INCREMENTAL:NO
    \endcode

     \section1 Debugger Cannot Attach to Running Process on Linux

    GDB uses \c ptrace to attach to running processes. Some Linux distributions
    do not allow this, which stops all attempts to either directly attach to an
    existing process or use the \uicontrol {Run in terminal} option in \QC.

    The reasons for this are described in
    \l{http://wiki.ubuntu.com/SecurityTeam/Roadmap/KernelHardening#ptrace%20Protection}
    {KernelHardening}.

    However, the usefulness of this security measure seems dubious because this
    feature can be easily disabled. With root permissions, you can disable the
    feature temporarily by writing \c{0} into
    \c{/proc/sys/kernel/yama/ptrace_scope} or permanently by changing the value
    in \c{/etc/sysctl.d/10-ptrace.conf}. Even if you do not have elevated
    permissions, you can disable the feature later by adding a library that
    calls \c{prctl(0x59616d61, getppid(), 0, 0, 0);}, such as the one in
    \c{$QTCREATORDIR/lib/libptracepreload.so} to the LD_PRELOAD environment.

*/