hhvm/hphp/runtime/debugger/cmd/cmd_flow_control.h

/*
   +----------------------------------------------------------------------+
   | HipHop for PHP                                                       |
   +----------------------------------------------------------------------+
   | Copyright (c) 2010-2013 Facebook, Inc. (http://www.facebook.com)     |
   +----------------------------------------------------------------------+
   | This source file is subject to version 3.01 of the PHP license,      |
   | that is bundled with this package in the file LICENSE, and is        |
   | available through the world-wide-web at the following url:           |
   | http://www.php.net/license/3_01.txt                                  |
   | If you did not receive a copy of the PHP license and are unable to   |
   | obtain it through the world-wide-web, please send a note to          |
   | license@php.net so we can mail you a copy immediately.               |
   +----------------------------------------------------------------------+
*/

#ifndef incl_HPHP_EVAL_DEBUGGER_CMD_FLOW_CONTROL_H_
#define incl_HPHP_EVAL_DEBUGGER_CMD_FLOW_CONTROL_H_

#include "hphp/runtime/debugger/debugger_command.h"
#include "hphp/runtime/debugger/cmd/cmd_interrupt.h"

namespace HPHP { namespace Eval {
///////////////////////////////////////////////////////////////////////////////
// CmdFlowControl is the base class of all "flow control" cmds: Continue, Step,
// Next, and Out. A DebuggerProxy can execute exactly one of these cmds at a
// time.
//
// 1. Proxy receives a flow command (say, Next).
// 2. Proxy calls the cmd's onSetup() with current source position.
// 3. Cmd sets up state (see below) in the VM to control stepping, etc.
// 4. If the cmd is complete the proxy deletes the cmd, otherwise it saves it
//    in m_flow.
// 5. Proxy lets the thread continue execution.
// 6. Proxy receives an interrupt from the VM, delivers it to the cmd in m_flow.
// 7. Cmd inspects the site and VM state, and either decides it is done, or
//    sets up state in the VM to continue the control flow operation.
// 8. If the cmd is complete the proxy stops and waits for more input from the
//    client. Otherwise, rinse and repeat at step 5.
//
// When a cmd is setup, or receives an interrupt and determines it is not
// complete, it will do one of three things to ensure it gets interrupted again
// in the future:
//
// 1. Set m_needsVMInterrupt to true, to ensure we interpret and interrupt on
//    each opcode executed.
// 2. Set m_needsVMInterrupt to true, and setup a location filter. This ensures
//    we interpret, but only interrupt when the PC misses the location filter.
// 3. Place an "internal breakpoint", which ensures an interrupt when the
//    breakpoint is hit without forcing us to interpret everything.
//
// The cmd may get interrupted for other reasons, such as an exception, reaching
// a breakpoint, a hard break, etc. All flow cmds are designed to tollerate this
// and remember enough state to determine if they should really transition their
// state or not.

DECLARE_BOOST_TYPES(CmdFlowControl);
class CmdFlowControl : public DebuggerCommand {
public:
  explicit CmdFlowControl(Type type)
    : DebuggerCommand(type), m_complete(false), m_needsVMInterrupt(false),
      m_stackDepth(0), m_vmDepth(0), m_count(1) { }
  virtual ~CmdFlowControl();

  virtual bool onServer(DebuggerProxy &proxy);
  virtual void onClient(DebuggerClient &client);

  // Work done to setup a new flow command, after receiving it from the client.
  virtual void onSetup(DebuggerProxy &proxy, CmdInterrupt &interrupt) = 0;

  // Work done when a VM thread interrupts the proxy.
  virtual void onBeginInterrupt(DebuggerProxy &proxy,
                                CmdInterrupt &interrupt) = 0;

  // A completed flow cmd has done all its work and can be deleted.
  bool complete() { return m_complete; }

  // Does this cmd need to force interrupts in the interpreter loop?
  bool needsVMInterrupt() { return m_needsVMInterrupt; }

protected:
  virtual void sendImpl(DebuggerThriftBuffer &thrift);
  virtual void recvImpl(DebuggerThriftBuffer &thrift);

  int decCount() { assert(m_count > 0); return --m_count;}
  int getCount() const { assert(m_count > 0); return m_count;}
  void installLocationFilterForLine(InterruptSite *site);
  void removeLocationFilter();
  void setupStepOuts();
  void cleanupStepOuts();
  bool hasStepOuts();
  bool atStepOutOffset(Unit* unit, Offset o);

  bool m_complete;
  bool m_needsVMInterrupt;

  // Support for stepping operations
  int m_stackDepth;
  int m_vmDepth;
  std::string m_loc; // last break's source location

  // Represents the destination of an internal stepping operation by
  // unit and offset. Implictly maintains the breakpoint filter.
  class StepDestination {
  public:
    StepDestination();
    StepDestination(const HPHP::Unit* unit, Offset offset);
    StepDestination(const StepDestination& other) = delete;
    StepDestination& operator=(const StepDestination& other) = delete;
    StepDestination(StepDestination&& other);
    StepDestination& operator=(StepDestination&& other);
    ~StepDestination();

    bool valid() const { return m_unit != nullptr; }
    bool at(const Unit* unit, Offset o) const {
      return (m_unit == unit) && (m_offset == o);
    }

  private:
    const HPHP::Unit* m_unit;
    Offset m_offset;
    bool m_ownsInternalBreakpoint;
  };

private:
  StepDestination m_stepOut1;
  StepDestination m_stepOut2;
  int16_t m_count;
  bool m_smallStep;
};

///////////////////////////////////////////////////////////////////////////////
}}

#endif // incl_HPHP_EVAL_DEBUGGER_CMD_FLOW_CONTROL_H_