darling-JavaScriptCore/debugger/Debugger.cpp

/*
 *  Copyright (C) 2008, 2013, 2014, 2016 Apple Inc. All rights reserved.
 *  Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
 *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library 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
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#include "config.h"
#include "Debugger.h"

#include "CodeBlock.h"
#include "DebuggerCallFrame.h"
#include "Error.h"
#include "HeapIterationScope.h"
#include "Interpreter.h"
#include "JSCInlines.h"
#include "JSCJSValueInlines.h"
#include "JSFunction.h"
#include "JSGlobalObject.h"
#include "MarkedSpaceInlines.h"
#include "Parser.h"
#include "Protect.h"
#include "VMEntryScope.h"

namespace {

using namespace JSC;

struct GatherSourceProviders : public MarkedBlock::VoidFunctor {
    // FIXME: This is a mutable field because this isn't a C++ lambda.
    // https://bugs.webkit.org/show_bug.cgi?id=159644
    mutable HashSet<SourceProvider*> sourceProviders;
    JSGlobalObject* m_globalObject;

    GatherSourceProviders(JSGlobalObject* globalObject)
        : m_globalObject(globalObject) { }

    IterationStatus operator()(HeapCell* heapCell, HeapCell::Kind kind) const
    {
        if (kind != HeapCell::JSCell)
            return IterationStatus::Continue;
        
        JSCell* cell = static_cast<JSCell*>(heapCell);
        
        JSFunction* function = jsDynamicCast<JSFunction*>(*cell->vm(), cell);
        if (!function)
            return IterationStatus::Continue;

        if (function->scope()->globalObject() != m_globalObject)
            return IterationStatus::Continue;

        if (!function->executable()->isFunctionExecutable())
            return IterationStatus::Continue;

        if (function->isHostOrBuiltinFunction())
            return IterationStatus::Continue;

        sourceProviders.add(
            jsCast<FunctionExecutable*>(function->executable())->source().provider());
        return IterationStatus::Continue;
    }
};

} // namespace

namespace JSC {

class DebuggerPausedScope {
public:
    DebuggerPausedScope(Debugger& debugger)
        : m_debugger(debugger)
    {
        ASSERT(!m_debugger.m_currentDebuggerCallFrame);
    }

    ~DebuggerPausedScope()
    {
        if (m_debugger.m_currentDebuggerCallFrame) {
            m_debugger.m_currentDebuggerCallFrame->invalidate();
            m_debugger.m_currentDebuggerCallFrame = nullptr;
        }
    }

private:
    Debugger& m_debugger;
};

// This is very similar to SetForScope<bool>, but that cannot be used
// as the m_isPaused field uses only one bit.
class TemporaryPausedState {
public:
    TemporaryPausedState(Debugger& debugger)
        : m_debugger(debugger)
    {
        ASSERT(!m_debugger.m_isPaused);
        m_debugger.m_isPaused = true;
    }

    ~TemporaryPausedState()
    {
        m_debugger.m_isPaused = false;
    }

private:
    Debugger& m_debugger;
};


Debugger::ProfilingClient::~ProfilingClient()
{
}

Debugger::Debugger(VM& vm)
    : m_vm(vm)
    , m_pauseOnExceptionsState(DontPauseOnExceptions)
    , m_pauseAtNextOpportunity(false)
    , m_pastFirstExpressionInStatement(false)
    , m_isPaused(false)
    , m_breakpointsActivated(false)
    , m_hasHandlerForExceptionCallback(false)
    , m_suppressAllPauses(false)
    , m_steppingMode(SteppingModeDisabled)
    , m_reasonForPause(NotPaused)
    , m_lastExecutedLine(UINT_MAX)
    , m_lastExecutedSourceID(noSourceID)
    , m_topBreakpointID(noBreakpointID)
    , m_pausingBreakpointID(noBreakpointID)
{
}

Debugger::~Debugger()
{
    HashSet<JSGlobalObject*>::iterator end = m_globalObjects.end();
    for (HashSet<JSGlobalObject*>::iterator it = m_globalObjects.begin(); it != end; ++it)
        (*it)->setDebugger(nullptr);
}

void Debugger::attach(JSGlobalObject* globalObject)
{
    ASSERT(!globalObject->debugger());
    globalObject->setDebugger(this);
    m_globalObjects.add(globalObject);

    m_vm.setShouldBuildPCToCodeOriginMapping();

    // Call sourceParsed because it will execute JavaScript in the inspector.
    GatherSourceProviders gatherSourceProviders(globalObject);
    {
        HeapIterationScope iterationScope(m_vm.heap);
        m_vm.heap.objectSpace().forEachLiveCell(iterationScope, gatherSourceProviders);
    }
    for (auto* sourceProvider : gatherSourceProviders.sourceProviders)
        sourceParsed(globalObject->globalExec(), sourceProvider, -1, String());
}

void Debugger::detach(JSGlobalObject* globalObject, ReasonForDetach reason)
{
    // If we're detaching from the currently executing global object, manually tear down our
    // stack, since we won't get further debugger callbacks to do so. Also, resume execution,
    // since there's no point in staying paused once a window closes.
    // We know there is an entry scope, otherwise, m_currentCallFrame would be null.
    if (m_isPaused && m_currentCallFrame && globalObject->vm().entryScope->globalObject() == globalObject) {
        m_currentCallFrame = nullptr;
        m_pauseOnCallFrame = nullptr;
        continueProgram();
    }

    ASSERT(m_globalObjects.contains(globalObject));
    m_globalObjects.remove(globalObject);

    // If the globalObject is destructing, then its CodeBlocks will also be
    // destructed. There is no need to do the debugger requests clean up, and
    // it is not safe to access those CodeBlocks at this time anyway.
    if (reason != GlobalObjectIsDestructing)
        clearDebuggerRequests(globalObject);

    globalObject->setDebugger(nullptr);

    if (m_globalObjects.isEmpty())
        clearParsedData();
}

bool Debugger::isAttached(JSGlobalObject* globalObject)
{
    return globalObject->debugger() == this;
}

class Debugger::SetSteppingModeFunctor {
public:
    SetSteppingModeFunctor(Debugger* debugger, SteppingMode mode)
        : m_debugger(debugger)
        , m_mode(mode)
    {
    }

    bool operator()(CodeBlock* codeBlock) const
    {
        if (m_debugger == codeBlock->globalObject()->debugger()) {
            if (m_mode == SteppingModeEnabled)
                codeBlock->setSteppingMode(CodeBlock::SteppingModeEnabled);
            else
                codeBlock->setSteppingMode(CodeBlock::SteppingModeDisabled);
        }
        return false;
    }

private:
    Debugger* m_debugger;
    SteppingMode m_mode;
};

void Debugger::setSteppingMode(SteppingMode mode)
{
    if (mode == m_steppingMode)
        return;

    m_vm.heap.completeAllJITPlans();

    m_steppingMode = mode;
    SetSteppingModeFunctor functor(this, mode);
    m_vm.heap.forEachCodeBlock(functor);
}

void Debugger::registerCodeBlock(CodeBlock* codeBlock)
{
    applyBreakpoints(codeBlock);
    if (isStepping())
        codeBlock->setSteppingMode(CodeBlock::SteppingModeEnabled);
}

void Debugger::setProfilingClient(ProfilingClient* client)
{
    ASSERT(!!m_profilingClient != !!client);
    m_profilingClient = client;
}

double Debugger::willEvaluateScript()
{
    return m_profilingClient->willEvaluateScript();
}

void Debugger::didEvaluateScript(double startTime, ProfilingReason reason)
{
    m_profilingClient->didEvaluateScript(startTime, reason);
}

void Debugger::toggleBreakpoint(CodeBlock* codeBlock, Breakpoint& breakpoint, BreakpointState enabledOrNot)
{
    ASSERT(breakpoint.resolved);

    ScriptExecutable* executable = codeBlock->ownerScriptExecutable();

    SourceID sourceID = static_cast<SourceID>(executable->sourceID());
    if (breakpoint.sourceID != sourceID)
        return;

    unsigned line = breakpoint.line;
    unsigned column = breakpoint.column;

    unsigned startLine = executable->firstLine();
    unsigned startColumn = executable->startColumn();
    unsigned endLine = executable->lastLine();
    unsigned endColumn = executable->endColumn();

    // Inspector breakpoint line and column values are zero-based but the executable
    // and CodeBlock line and column values are one-based.
    line += 1;
    column = column ? column + 1 : Breakpoint::unspecifiedColumn;

    if (line < startLine || line > endLine)
        return;
    if (column != Breakpoint::unspecifiedColumn) {
        if (line == startLine && column < startColumn)
            return;
        if (line == endLine && column > endColumn)
            return;
    }

    if (!codeBlock->hasOpDebugForLineAndColumn(line, column))
        return;

    if (enabledOrNot == BreakpointEnabled)
        codeBlock->addBreakpoint(1);
    else
        codeBlock->removeBreakpoint(1);
}

void Debugger::applyBreakpoints(CodeBlock* codeBlock)
{
    BreakpointIDToBreakpointMap& breakpoints = m_breakpointIDToBreakpoint;
    for (auto* breakpoint : breakpoints.values())
        toggleBreakpoint(codeBlock, *breakpoint, BreakpointEnabled);
}

class Debugger::ToggleBreakpointFunctor {
public:
    ToggleBreakpointFunctor(Debugger* debugger, Breakpoint& breakpoint, BreakpointState enabledOrNot)
        : m_debugger(debugger)
        , m_breakpoint(breakpoint)
        , m_enabledOrNot(enabledOrNot)
    {
    }

    bool operator()(CodeBlock* codeBlock) const
    {
        if (m_debugger == codeBlock->globalObject()->debugger())
            m_debugger->toggleBreakpoint(codeBlock, m_breakpoint, m_enabledOrNot);
        return false;
    }

private:
    Debugger* m_debugger;
    Breakpoint& m_breakpoint;
    BreakpointState m_enabledOrNot;
};

void Debugger::toggleBreakpoint(Breakpoint& breakpoint, Debugger::BreakpointState enabledOrNot)
{
    m_vm.heap.completeAllJITPlans();

    ToggleBreakpointFunctor functor(this, breakpoint, enabledOrNot);
    m_vm.heap.forEachCodeBlock(functor);
}

void Debugger::recompileAllJSFunctions()
{
    m_vm.deleteAllCode(PreventCollectionAndDeleteAllCode);
}

DebuggerParseData& Debugger::debuggerParseData(SourceID sourceID, SourceProvider* provider)
{
    auto iter = m_parseDataMap.find(sourceID);
    if (iter != m_parseDataMap.end())
        return iter->value;

    DebuggerParseData parseData;
    gatherDebuggerParseDataForSource(m_vm, provider, parseData);
    auto result = m_parseDataMap.add(sourceID, parseData);
    return result.iterator->value;
}

void Debugger::resolveBreakpoint(Breakpoint& breakpoint, SourceProvider* sourceProvider)
{
    RELEASE_ASSERT(!breakpoint.resolved);
    ASSERT(breakpoint.sourceID != noSourceID);

    // FIXME: <https://webkit.org/b/162771> Web Inspector: Adopt TextPosition in Inspector to avoid oneBasedInt/zeroBasedInt ambiguity
    // Inspector breakpoint line and column values are zero-based but the executable
    // and CodeBlock line and column values are one-based.
    unsigned line = breakpoint.line + 1;
    unsigned column = breakpoint.column ? breakpoint.column : Breakpoint::unspecifiedColumn;

    DebuggerParseData& parseData = debuggerParseData(breakpoint.sourceID, sourceProvider);
    std::optional<JSTextPosition> resolvedPosition = parseData.pausePositions.breakpointLocationForLineColumn((int)line, (int)column);
    if (!resolvedPosition)
        return;

    unsigned resolvedLine = resolvedPosition->line;
    unsigned resolvedColumn = resolvedPosition->offset - resolvedPosition->lineStartOffset + 1;

    breakpoint.line = resolvedLine - 1;
    breakpoint.column = resolvedColumn - 1;
    breakpoint.resolved = true;
}

BreakpointID Debugger::setBreakpoint(Breakpoint& breakpoint, bool& existing)
{
    ASSERT(breakpoint.resolved);
    ASSERT(breakpoint.sourceID != noSourceID);

    SourceID sourceID = breakpoint.sourceID;
    unsigned line = breakpoint.line;
    unsigned column = breakpoint.column;

    SourceIDToBreakpointsMap::iterator it = m_sourceIDToBreakpoints.find(breakpoint.sourceID);
    if (it == m_sourceIDToBreakpoints.end())
        it = m_sourceIDToBreakpoints.set(sourceID, LineToBreakpointsMap()).iterator;

    LineToBreakpointsMap::iterator breaksIt = it->value.find(line);
    if (breaksIt == it->value.end())
        breaksIt = it->value.set(line, adoptRef(new BreakpointsList)).iterator;

    BreakpointsList& breakpoints = *breaksIt->value;
    for (Breakpoint* current = breakpoints.head(); current; current = current->next()) {
        if (current->column == column) {
            // Found existing breakpoint. Do not create a duplicate at this location.
            existing = true;
            return current->id;
        }
    }

    existing = false;
    BreakpointID id = ++m_topBreakpointID;
    RELEASE_ASSERT(id != noBreakpointID);

    breakpoint.id = id;

    Breakpoint* newBreakpoint = new Breakpoint(breakpoint);
    breakpoints.append(newBreakpoint);
    m_breakpointIDToBreakpoint.set(id, newBreakpoint);

    toggleBreakpoint(*newBreakpoint, BreakpointEnabled);

    return id;
}

void Debugger::removeBreakpoint(BreakpointID id)
{
    ASSERT(id != noBreakpointID);

    BreakpointIDToBreakpointMap::iterator idIt = m_breakpointIDToBreakpoint.find(id);
    ASSERT(idIt != m_breakpointIDToBreakpoint.end());
    Breakpoint* breakpoint = idIt->value;

    SourceID sourceID = breakpoint->sourceID;
    ASSERT(sourceID);
    SourceIDToBreakpointsMap::iterator it = m_sourceIDToBreakpoints.find(sourceID);
    ASSERT(it != m_sourceIDToBreakpoints.end());
    LineToBreakpointsMap::iterator breaksIt = it->value.find(breakpoint->line);
    ASSERT(breaksIt != it->value.end());

    toggleBreakpoint(*breakpoint, BreakpointDisabled);

    BreakpointsList& breakpoints = *breaksIt->value;
#if !ASSERT_DISABLED
    bool found = false;
    for (Breakpoint* current = breakpoints.head(); current && !found; current = current->next()) {
        if (current->id == breakpoint->id)
            found = true;
    }
    ASSERT(found);
#endif

    m_breakpointIDToBreakpoint.remove(idIt);
    breakpoints.remove(breakpoint);
    delete breakpoint;

    if (breakpoints.isEmpty()) {
        it->value.remove(breaksIt);
        if (it->value.isEmpty())
            m_sourceIDToBreakpoints.remove(it);
    }
}

bool Debugger::hasBreakpoint(SourceID sourceID, const TextPosition& position, Breakpoint *hitBreakpoint)
{
    if (!m_breakpointsActivated)
        return false;

    SourceIDToBreakpointsMap::const_iterator it = m_sourceIDToBreakpoints.find(sourceID);
    if (it == m_sourceIDToBreakpoints.end())
        return false;

    unsigned line = position.m_line.zeroBasedInt();
    unsigned column = position.m_column.zeroBasedInt();
    
    LineToBreakpointsMap::const_iterator breaksIt = it->value.find(line);
    if (breaksIt == it->value.end())
        return false;

    bool hit = false;
    const BreakpointsList& breakpoints = *breaksIt->value;
    Breakpoint* breakpoint;
    for (breakpoint = breakpoints.head(); breakpoint; breakpoint = breakpoint->next()) {
        unsigned breakLine = breakpoint->line;
        unsigned breakColumn = breakpoint->column;
        // Since frontend truncates the indent, the first statement in a line must match the breakpoint (line,0).
        ASSERT(this == m_currentCallFrame->codeBlock()->globalObject()->debugger());
        if ((line != m_lastExecutedLine && line == breakLine && !breakColumn)
            || (line == breakLine && column == breakColumn)) {
            hit = true;
            break;
        }
    }
    if (!hit)
        return false;

    if (hitBreakpoint)
        *hitBreakpoint = *breakpoint;

    breakpoint->hitCount++;
    if (breakpoint->ignoreCount >= breakpoint->hitCount)
        return false;

    if (breakpoint->condition.isEmpty())
        return true;

    // We cannot stop in the debugger while executing condition code,
    // so make it looks like the debugger is already paused.
    TemporaryPausedState pausedState(*this);

    NakedPtr<Exception> exception;
    DebuggerCallFrame& debuggerCallFrame = currentDebuggerCallFrame();
    JSObject* scopeExtensionObject = nullptr;
    JSValue result = debuggerCallFrame.evaluateWithScopeExtension(breakpoint->condition, scopeExtensionObject, exception);

    // We can lose the debugger while executing JavaScript.
    if (!m_currentCallFrame)
        return false;

    if (exception) {
        // An erroneous condition counts as "false".
        handleExceptionInBreakpointCondition(m_currentCallFrame, exception);
        return false;
    }

    return result.toBoolean(m_currentCallFrame);
}

class Debugger::ClearCodeBlockDebuggerRequestsFunctor {
public:
    ClearCodeBlockDebuggerRequestsFunctor(Debugger* debugger)
        : m_debugger(debugger)
    {
    }

    bool operator()(CodeBlock* codeBlock) const
    {
        if (codeBlock->hasDebuggerRequests() && m_debugger == codeBlock->globalObject()->debugger())
            codeBlock->clearDebuggerRequests();
        return false;
    }

private:
    Debugger* m_debugger;
};

void Debugger::clearBreakpoints()
{
    m_vm.heap.completeAllJITPlans();

    m_topBreakpointID = noBreakpointID;
    m_breakpointIDToBreakpoint.clear();
    m_sourceIDToBreakpoints.clear();

    ClearCodeBlockDebuggerRequestsFunctor functor(this);
    m_vm.heap.forEachCodeBlock(functor);
}

class Debugger::ClearDebuggerRequestsFunctor {
public:
    ClearDebuggerRequestsFunctor(JSGlobalObject* globalObject)
        : m_globalObject(globalObject)
    {
    }

    bool operator()(CodeBlock* codeBlock) const
    {
        if (codeBlock->hasDebuggerRequests() && m_globalObject == codeBlock->globalObject())
            codeBlock->clearDebuggerRequests();
        return false;
    }

private:
    JSGlobalObject* m_globalObject;
};

void Debugger::clearDebuggerRequests(JSGlobalObject* globalObject)
{
    m_vm.heap.completeAllJITPlans();

    ClearDebuggerRequestsFunctor functor(globalObject);
    m_vm.heap.forEachCodeBlock(functor);
}

void Debugger::clearParsedData()
{
    m_parseDataMap.clear();
}

void Debugger::setBreakpointsActivated(bool activated)
{
    if (activated == m_breakpointsActivated)
        return;

    m_breakpointsActivated = activated;
    recompileAllJSFunctions();
}

void Debugger::setPauseOnExceptionsState(PauseOnExceptionsState pause)
{
    m_pauseOnExceptionsState = pause;
}

void Debugger::setPauseOnNextStatement(bool pause)
{
    m_pauseAtNextOpportunity = pause;
    if (pause)
        setSteppingMode(SteppingModeEnabled);
}

void Debugger::breakProgram()
{
    if (m_isPaused)
        return;

    if (!m_vm.topCallFrame)
        return;

    m_pauseAtNextOpportunity = true;
    setSteppingMode(SteppingModeEnabled);
    m_currentCallFrame = m_vm.topCallFrame;
    pauseIfNeeded(m_currentCallFrame);
}

void Debugger::continueProgram()
{
    clearNextPauseState();

    if (!m_isPaused)
        return;

    notifyDoneProcessingDebuggerEvents();
}

void Debugger::stepIntoStatement()
{
    if (!m_isPaused)
        return;

    m_pauseAtNextOpportunity = true;
    setSteppingMode(SteppingModeEnabled);
    notifyDoneProcessingDebuggerEvents();
}

void Debugger::stepOverStatement()
{
    if (!m_isPaused)
        return;

    m_pauseOnCallFrame = m_currentCallFrame;
    setSteppingMode(SteppingModeEnabled);
    notifyDoneProcessingDebuggerEvents();
}

void Debugger::stepOutOfFunction()
{
    if (!m_isPaused)
        return;

    VMEntryFrame* topVMEntryFrame = m_vm.topVMEntryFrame;
    m_pauseOnCallFrame = m_currentCallFrame ? m_currentCallFrame->callerFrame(topVMEntryFrame) : nullptr;
    m_pauseOnStepOut = true;
    setSteppingMode(SteppingModeEnabled);
    notifyDoneProcessingDebuggerEvents();
}

void Debugger::updateCallFrame(CallFrame* callFrame, CallFrameUpdateAction action)
{
    if (!callFrame) {
        m_currentCallFrame = nullptr;
        return;
    }

    updateCallFrameInternal(callFrame);

    if (action == AttemptPause)
        pauseIfNeeded(callFrame);

    if (!isStepping())
        m_currentCallFrame = nullptr;
}

void Debugger::updateCallFrameInternal(CallFrame* callFrame)
{
    m_currentCallFrame = callFrame;
    SourceID sourceID = DebuggerCallFrame::sourceIDForCallFrame(callFrame);
    if (m_lastExecutedSourceID != sourceID) {
        m_lastExecutedLine = UINT_MAX;
        m_lastExecutedSourceID = sourceID;
    }
}

void Debugger::pauseIfNeeded(CallFrame* callFrame)
{
    VM& vm = m_vm;
    auto scope = DECLARE_THROW_SCOPE(vm);

    if (m_isPaused)
        return;

    if (m_suppressAllPauses)
        return;

    intptr_t sourceID = DebuggerCallFrame::sourceIDForCallFrame(m_currentCallFrame);
    if (isBlacklisted(sourceID))
        return;

    DebuggerPausedScope debuggerPausedScope(*this);

    bool pauseNow = m_pauseAtNextOpportunity;
    pauseNow |= (m_pauseOnCallFrame == m_currentCallFrame);

    bool didPauseForStep = pauseNow;

    Breakpoint breakpoint;
    TextPosition position = DebuggerCallFrame::positionForCallFrame(vm, m_currentCallFrame);
    bool didHitBreakpoint = hasBreakpoint(sourceID, position, &breakpoint);
    pauseNow |= didHitBreakpoint;
    m_lastExecutedLine = position.m_line.zeroBasedInt();
    if (!pauseNow)
        return;

    clearNextPauseState();

    // Make sure we are not going to pause again on breakpoint actions by
    // reseting the pause state before executing any breakpoint actions.
    TemporaryPausedState pausedState(*this);

    JSGlobalObject* vmEntryGlobalObject = callFrame->vmEntryGlobalObject(vm);

    if (didHitBreakpoint) {
        handleBreakpointHit(vmEntryGlobalObject, breakpoint);
        // Note that the actions can potentially stop the debugger, so we need to check that
        // we still have a current call frame when we get back.
        if (!m_currentCallFrame)
            return;

        if (breakpoint.autoContinue) {
            if (!didPauseForStep)
                return;
            didHitBreakpoint = false;
        } else
            m_pausingBreakpointID = breakpoint.id;
    }

    {
        PauseReasonDeclaration reason(*this, didHitBreakpoint ? PausedForBreakpoint : m_reasonForPause);
        handlePause(vmEntryGlobalObject, m_reasonForPause);
        scope.releaseAssertNoException();
    }

    m_pausingBreakpointID = noBreakpointID;

    if (!m_pauseAtNextOpportunity && !m_pauseOnCallFrame) {
        setSteppingMode(SteppingModeDisabled);
        m_currentCallFrame = nullptr;
    }
}

void Debugger::exception(CallFrame* callFrame, JSValue exception, bool hasCatchHandler)
{
    if (m_isPaused)
        return;

    if (JSObject* object = jsDynamicCast<JSObject*>(m_vm, exception)) {
        if (object->isErrorInstance()) {
            ErrorInstance* error = static_cast<ErrorInstance*>(object);
            // FIXME: <https://webkit.org/b/173625> Web Inspector: Should be able to pause and debug a StackOverflow Exception
            // FIXME: <https://webkit.org/b/173627> Web Inspector: Should be able to pause and debug an OutOfMemory Exception
            if (error->isStackOverflowError() || error->isOutOfMemoryError())
                return;
        }
    }

    PauseReasonDeclaration reason(*this, PausedForException);
    if (m_pauseOnExceptionsState == PauseOnAllExceptions || (m_pauseOnExceptionsState == PauseOnUncaughtExceptions && !hasCatchHandler)) {
        m_pauseAtNextOpportunity = true;
        setSteppingMode(SteppingModeEnabled);
    }

    m_hasHandlerForExceptionCallback = true;
    m_currentException = exception;
    updateCallFrame(callFrame, AttemptPause);
    m_currentException = JSValue();
    m_hasHandlerForExceptionCallback = false;
}

void Debugger::atStatement(CallFrame* callFrame)
{
    if (m_isPaused)
        return;

    m_pastFirstExpressionInStatement = false;

    PauseReasonDeclaration reason(*this, PausedAtStatement);
    updateCallFrame(callFrame, AttemptPause);
}

void Debugger::atExpression(CallFrame* callFrame)
{
    if (m_isPaused)
        return;

    // If this is the first call in a statement, then we would have paused at the statement.
    if (!m_pastFirstExpressionInStatement) {
        m_pastFirstExpressionInStatement = true;
        return;
    }

    // Only pause at the next expression with step-in and step-out, not step-over.
    bool shouldAttemptPause = m_pauseAtNextOpportunity || m_pauseOnStepOut;

    PauseReasonDeclaration reason(*this, PausedAtExpression);
    updateCallFrame(callFrame, shouldAttemptPause ? AttemptPause : NoPause);
}

void Debugger::callEvent(CallFrame* callFrame)
{
    if (m_isPaused)
        return;

    updateCallFrame(callFrame, NoPause);
}

void Debugger::returnEvent(CallFrame* callFrame)
{
    if (m_isPaused)
        return;

    {
        PauseReasonDeclaration reason(*this, PausedBeforeReturn);
        updateCallFrame(callFrame, AttemptPause);
    }

    // Detach may have been called during pauseIfNeeded.
    if (!m_currentCallFrame)
        return;

    VMEntryFrame* topVMEntryFrame = m_vm.topVMEntryFrame;
    CallFrame* callerFrame = m_currentCallFrame->callerFrame(topVMEntryFrame);

    // Returning from a call, there was at least one expression on the statement we are returning to.
    m_pastFirstExpressionInStatement = true;

    // Treat stepping over a return statement like a step-out.
    if (m_currentCallFrame == m_pauseOnCallFrame) {
        m_pauseOnCallFrame = callerFrame;
        m_pauseOnStepOut = true;
    }

    updateCallFrame(callerFrame, NoPause);
}

void Debugger::unwindEvent(CallFrame* callFrame)
{
    if (m_isPaused)
        return;

    updateCallFrame(callFrame, NoPause);

    if (!m_currentCallFrame)
        return;

    VMEntryFrame* topVMEntryFrame = m_vm.topVMEntryFrame;
    CallFrame* callerFrame = m_currentCallFrame->callerFrame(topVMEntryFrame);

    // Treat stepping over an exception location like a step-out.
    if (m_currentCallFrame == m_pauseOnCallFrame)
        m_pauseOnCallFrame = callerFrame;

    updateCallFrame(callerFrame, NoPause);
}

void Debugger::willExecuteProgram(CallFrame* callFrame)
{
    if (m_isPaused)
        return;

    updateCallFrame(callFrame, NoPause);
}

void Debugger::didExecuteProgram(CallFrame* callFrame)
{
    if (m_isPaused)
        return;

    PauseReasonDeclaration reason(*this, PausedAtEndOfProgram);
    updateCallFrame(callFrame, AttemptPause);

    // Detach may have been called during pauseIfNeeded.
    if (!m_currentCallFrame)
        return;

    VMEntryFrame* topVMEntryFrame = m_vm.topVMEntryFrame;
    CallFrame* callerFrame = m_currentCallFrame->callerFrame(topVMEntryFrame);

    // Returning from a program, could be eval(), there was at least one expression on the statement we are returning to.
    m_pastFirstExpressionInStatement = true;

    // Treat stepping over the end of a program like a step-out.
    if (m_currentCallFrame == m_pauseOnCallFrame) {
        m_pauseOnCallFrame = callerFrame;
        m_pauseAtNextOpportunity = true;
    }

    updateCallFrame(callerFrame, NoPause);

    // Do not continue stepping into an unknown future program.
    if (!m_currentCallFrame)
        clearNextPauseState();
}

void Debugger::clearNextPauseState()
{
    m_pauseOnCallFrame = nullptr;
    m_pauseAtNextOpportunity = false;
    m_pauseOnStepOut = false;
}

void Debugger::didReachBreakpoint(CallFrame* callFrame)
{
    if (m_isPaused)
        return;

    PauseReasonDeclaration reason(*this, PausedForDebuggerStatement);
    m_pauseAtNextOpportunity = true;
    setSteppingMode(SteppingModeEnabled);
    updateCallFrame(callFrame, AttemptPause);
}

DebuggerCallFrame& Debugger::currentDebuggerCallFrame()
{
    if (!m_currentDebuggerCallFrame)
        m_currentDebuggerCallFrame = DebuggerCallFrame::create(m_vm, m_currentCallFrame);
    return *m_currentDebuggerCallFrame;
}

bool Debugger::isBlacklisted(SourceID sourceID) const
{
    return m_blacklistedScripts.contains(sourceID);
}

void Debugger::addToBlacklist(SourceID sourceID)
{
    m_blacklistedScripts.add(sourceID);
}

void Debugger::clearBlacklist()
{
    m_blacklistedScripts.clear();
}

} // namespace JSC