TDebuggerIntf

TDebuggerIntf is the base class of implementing a debugger as Lazarus-IDE plugin package. The package must have DebuggerIntf package as it's requirements. Any debugger plug-in must implement the class and register via RegisterDebugger (called at Register of registering unit).

Implementation notes:

• the class is designed to act as asynchronous object. The interaction is implemented in form of commands sent to the class.
• the command should be put (or not put) into an execution queue. The information about acceptance or denial of the command should be returned as soon as possible.

Command request is sent from the Main Thread. Thus any actual debugging job should be implemented in a separate thread NOT to impact the user experience.

• once a command has been handled from the queue, the corresponding event should be called and/or debugger state changed

Minimal Implementation

The following methods must be implemented for TDebbugerIntf

• GetSupportedCommands (or GetCommands) - returns the set of formats that a debugger can perform
• RequestCommand - the method actually performing commands. Only commands returned by GetSupportedCommands would be passed to this method
• Caption - the method return user-friendly name of the debugger

type
  TMiniDebugger = class(TDebuggerIntf)
  protected
    function RequestCommand(const ACommand: TDBGCommand; const AParams: array of const): Boolean; override;
    function GetSupportedCommands: TDBGCommands; override;
  public
    class function Caption: String; override;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterDebugger(TMiniDebugger);
end;

class function TMiniDebugger.Caption: String;
begin
  Result:='Initial Debugger Plug-in';
end;

function TMiniDebugger.GetSupportedCommands: TDBGCommands;
begin
  Result := [dcRun, dcStop];
end;
      
function TMiniDebugger.RequestCommand(const ACommand: TDBGCommand;
  const AParams: array of const): Boolean;
begin
  case ACommand of
    dcRun: begin       // the debugger was requested to run
      Result:=true;    // typically it should set the state into dsIdle (to get more data from IDE)
      SetState(dsRun); // the debugger replies as if it started immediately 
    end;
    dcStop: begin      // the debugger was requested to stop
      Result:=true;
      SetState(dsStop); // the debugger replied as if it stopped immediately
    end;
  else
    Result:=false;
  end;
end;

Methods

RequestCommand

The method should return false, if the command cannot be executed.

Debugger Commands

Command	Explanation	Parameters
dcRun	Starts (or Restarts) or Resumes the execution of a debugged process. The debugged process executable and arguments to be used are available through FileName and Arguments properties of TDebuggerIntf object.	no parameters
dcPause		no parameters
dcStop		no parameters
dcStepOver		no parameters
dcStepInto		no parameters
dcStepOut		no parameters
dcRunTo		0 - AnsiString - file name of the source code to run to 1 - Integer - Line number to run to
dcJumpto		0 - AnsiString - file name of the source code to jump to 1 - Integer - Line number to run to
dcAttach		0 - AnsiString - process ID to attach-to.
dcDetach		no parameters
dcBreak
dcWatch
dcLocal
dcEvaluate		0 - AnsiString - expression to be evaluated 1 - pointer to AnsiString - the string where the result should be saved into 2 - pointer to TDBGType - the reference where the information about the result type should be saved to 3 - Integer - TDBGEvaluateFlags casted into Integer
dcModify	Modifies the given expression / Assigns a value to a variable/field/property	0 - AnsiString - identified expression 1 - AnsiString - value to be assigned
dcEnvironment
dcSetStackFrame
dcDisassemble
dcStepOverInstr
dcStepIntoInstr
dcSendConsoleInput

Development Hints

• it might be helpful to recompile DebuggerIntf package, adding the following Custom Options to the compiler options of the package

-dDBG_STATE

-dDBG_EVENTS

-dDBG_VERBOSE

-dDBG_WARNINGS

-dDBG_DATA_MONITORS

-dDBG_DISASSEMBLER

these defines provide more logging output of TDebuggerIntf

• it might be helpful to rebuild IDE adding the following defines into build Options:

-dVerboseDebugger

VerboseDebugger logs messages debugging calls from IDE itself

See Also

• FpGdbmiDebugger - debugger plug-in, that works over the external GDB debugger, but has a better understanding of Pascal expressions and types