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* Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package com.oracle.truffle.api.debug;
import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
import com.oracle.truffle.api.Truffle;
import com.oracle.truffle.api.debug.DebuggerSession.SteppingLocation;
import com.oracle.truffle.api.frame.FrameInstance;
import com.oracle.truffle.api.frame.FrameInstanceVisitor;
import com.oracle.truffle.api.instrumentation.EventContext;
/**
* Implementation of a strategy for a debugger <em>action</em> that allows execution to continue
* until it reaches another location e.g "step in" vs. "step over".
*/
abstract class SteppingStrategy {
/*
* Indicates that a stepping strategy was consumed by an suspended event.
*/
private boolean consumed;
private SteppingStrategy next;
void consume() {
consumed = true;
}
boolean isConsumed() {
return consumed;
}
abstract boolean step(DebuggerSession steppingSession, EventContext context, SteppingLocation location);
abstract void initialize();
boolean isDone() {
return false;
}
boolean isKill() {
return false;
}
boolean isComposable() {
return false;
}
@SuppressWarnings("unused")
void add(SteppingStrategy nextStrategy) {
throw new UnsupportedOperationException("Not composable.");
}
static SteppingStrategy createKill() {
return new Kill();
}
static SteppingStrategy createAlwaysHalt() {
return new AlwaysHalt();
}
static SteppingStrategy createContinue() {
return new Continue();
}
static SteppingStrategy createStepInto(int stepCount) {
return new StepInto(stepCount);
}
static SteppingStrategy createStepOut(int stepCount) {
return new StepOut(stepCount);
}
static SteppingStrategy createStepOver(int stepCount) {
return new StepOver(stepCount);
}
static SteppingStrategy createComposed(SteppingStrategy strategy1, SteppingStrategy strategy2) {
return new ComposedStrategy(strategy1, strategy2);
}
// TODO (mlvdv) wish there were fast-path access to stack depth
// TODO (chumer) wish so too
@TruffleBoundary
private static int computeStackDepth() {
FrameInstanceCounter counter = new FrameInstanceCounter();
Truffle.getRuntime().iterateFrames(counter);
return counter.getCount() + 1;
}
private static class FrameInstanceCounter implements FrameInstanceVisitor<Void> {
private int count;
public Void visitFrame(FrameInstance frameInstance) {
count++;
return null;
}
public int getCount() {
return count;
}
}
private static final class Kill extends SteppingStrategy {
@Override
boolean step(DebuggerSession steppingSession, EventContext context, SteppingLocation location) {
return true;
}
@Override
void initialize() {
}
@Override
public boolean isDone() {
return true;
}
@Override
public boolean isKill() {
return true;
}
@Override
public String toString() {
return "KILL";
}
}
private static final class AlwaysHalt extends SteppingStrategy {
@Override
boolean step(DebuggerSession steppingSession, EventContext context, SteppingLocation location) {
return true;
}
@Override
void initialize() {
}
@Override
public String toString() {
return "HALT";
}
}
/**
* Strategy: the null stepping strategy.
* <ul>
* <li>User breakpoints are enabled.</li>
* <li>Execution continues until either:
* <ol>
* <li>execution arrives at a node with attached user breakpoint, <strong>or:</strong></li>
* <li>execution completes.</li>
* </ol>
* </ul>
*/
private static final class Continue extends SteppingStrategy {
@Override
boolean step(DebuggerSession steppingSession, EventContext context, SteppingLocation location) {
return false;
}
@Override
void initialize() {
}
@Override
public boolean isDone() {
return true;
}
@Override
public String toString() {
return "CONTINUE";
}
}
/**
* Strategy: per-{@link #HALT_TAG} stepping.
* <ul>
* <li>User breakpoints are enabled.</li>
* <li>Execution continues until either:
* <ol>
* <li>execution <em>arrives</em> at a {@link #HALT_TAG} node, <strong>or:</strong></li>
* <li>execution <em>returns</em> to a {@link #CALL_TAG} node and the call stack is smaller then
* when execution started, <strong>or:</strong></li>
* <li>execution completes.</li>
* </ol>
* </ul>
*
* @see Debugger#prepareStepInto(int)
*/
private static final class StepInto extends SteppingStrategy {
private int startStackDepth;
private int unfinishedStepCount;
StepInto(int stepCount) {
this.unfinishedStepCount = stepCount;
}
@Override
void initialize() {
this.startStackDepth = computeStackDepth();
}
@Override
boolean step(DebuggerSession steppingSession, EventContext context, SteppingLocation location) {
if (location == SteppingLocation.BEFORE_STATEMENT) {
if (--unfinishedStepCount <= 0) {
return true;
}
} else if (location == SteppingLocation.AFTER_CALL) {
if (computeStackDepth() < startStackDepth) {
if (--unfinishedStepCount <= 0) {
return true;
}
}
}
return false;
}
@Override
public String toString() {
return String.format("STEP_INTO(startStackDepth=%s, stepCount=%s)", startStackDepth, unfinishedStepCount);
}
}
/**
* Strategy: execution to nearest enclosing call site.
* <ul>
* <li>User breakpoints are enabled.</li>
* <li>Execution continues until either:
* <ol>
* <li>execution arrives at a node with attached user breakpoint, <strong>or:</strong></li>
* <li>execution <em>returns</em> to a CALL node and the call stack is smaller than when
* execution started, <strong>or:</strong></li>
* <li>execution completes.</li>
* </ol>
* </ul>
*
* @see Debugger#prepareStepOut()
*/
private static final class StepOut extends SteppingStrategy {
private int unfinishedStepCount;
private int startStackDepth;
StepOut(int stepCount) {
this.unfinishedStepCount = stepCount;
}
@Override
void initialize() {
this.startStackDepth = computeStackDepth();
}
@Override
boolean step(DebuggerSession steppingSession, EventContext context, SteppingLocation location) {
if (location == SteppingLocation.AFTER_CALL) {
if (computeStackDepth() < startStackDepth) {
if (--unfinishedStepCount <= 0) {
return true;
}
}
}
return false;
}
@Override
public String toString() {
return String.format("STEP_OUT(startStackDepth=%s, stepCount=%s)", startStackDepth, unfinishedStepCount);
}
}
/**
* Strategy: per-{@link #HALT_TAG} stepping, so long as not nested in method calls (i.e. at
* original stack depth).
* <ul>
* <li>User breakpoints are enabled.</li>
* <li>Execution continues until either:
* <ol>
* <li>execution arrives at a node holding {@link #HALT_TAG}, with stack depth no more than when
* started <strong>or:</strong></li>
* <li>the program completes.</li>
* </ol>
* </ul>
*/
private static final class StepOver extends SteppingStrategy {
private int startStackDepth;
private int unfinishedStepCount;
StepOver(int stepCount) {
this.unfinishedStepCount = stepCount;
}
@Override
void initialize() {
this.startStackDepth = computeStackDepth();
}
@Override
boolean step(DebuggerSession steppingSession, EventContext context, SteppingLocation location) {
if (location == SteppingLocation.BEFORE_STATEMENT) {
if (computeStackDepth() <= startStackDepth) {
if (--unfinishedStepCount <= 0) {
return true;
}
}
} else if (location == SteppingLocation.AFTER_CALL) {
if (computeStackDepth() < startStackDepth) {
if (--unfinishedStepCount <= 0) {
return true;
}
}
}
return false;
}
@Override
public String toString() {
return String.format("STEP_OVER(startStackDepth=%s, stepCount=%s)", startStackDepth, unfinishedStepCount);
}
}
static final class ComposedStrategy extends SteppingStrategy {
private final SteppingStrategy first;
private SteppingStrategy last;
private SteppingStrategy current;
private ComposedStrategy(SteppingStrategy strategy1, SteppingStrategy strategy2) {
strategy1.next = strategy2;
first = strategy1;
current = first;
last = strategy2;
}
@Override
void initialize() {
assert current == first;
current.initialize();
}
@Override
boolean step(DebuggerSession steppingSession, EventContext context, SteppingLocation location) {
boolean hit = current.step(steppingSession, context, location);
if (hit) {
if (current == last) {
return true;
} else {
current = current.next;
current.initialize();
}
}
return false;
}
@Override
void consume() {
assert current == last;
last.consume();
}
@Override
boolean isConsumed() {
assert current == last;
return last.isConsumed();
}
@Override
boolean isDone() {
if (current == last) {
return last.isDone();
}
return false;
}
@Override
boolean isKill() {
if (current == last) {
return last.isKill();
}
return false;
}
@Override
boolean isComposable() {
return true;
}
@Override
synchronized void add(SteppingStrategy nextStrategy) {
last.next = nextStrategy;
last = nextStrategy;
}
@Override
public String toString() {
StringBuilder all = new StringBuilder();
for (SteppingStrategy s = first; s.next != null; s = s.next) {
if (all.length() > 0) {
all.append(", ");
}
all.append(s.toString());
}
return "COMPOSED(" + all + ")";
}
}
}