Source/JavaScriptCore/runtime/VMTrapsInlines.h

/*
 * Copyright (C) 2021-2025 Apple Inc. All rights reserved.
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#pragma once

#include <JavaScriptCore/VM.h>

namespace JSC {

ALWAYS_INLINE VM& VMTraps::vm() const
{
    return *std::bit_cast<VM*>(std::bit_cast<uintptr_t>(this) - VM::offsetOfTraps());
}

inline void VMTraps::deferTermination(DeferAction deferAction)
{
    auto originalCount = m_deferTerminationCount++;
    ASSERT(m_deferTerminationCount < UINT_MAX);
    // Strictly speaking, we're only interested in vm.hasPendingTerminationException() here.
    // However, vm.exception() is a necessary condition for vm.hasPendingTerminationException().
    // Since this checks is intended to be cheap, we'll just do the cheaper check of vm.exception()
    // which itself rarely returns true. We'll let the slow path do the full
    // vm.hasPendingTerminationException() check instead.
    if (!originalCount && vm().exception()) [[unlikely]]
        deferTerminationSlow(deferAction);
}

inline void VMTraps::undoDeferTermination(DeferAction deferAction)
{
    ASSERT(m_deferTerminationCount > 0);
    ASSERT(!m_suspendedTerminationException || vm().hasTerminationRequest());
    if (!--m_deferTerminationCount && vm().hasTerminationRequest()) [[unlikely]]
        undoDeferTerminationSlow(deferAction);
}

ALWAYS_INLINE DeferTraps::DeferTraps(VM& vm)
    : m_traps(vm.traps())
    , m_previousTrapsDeferred(m_traps.m_trapsDeferred)
{
    m_traps.m_trapsDeferred = true;
}

ALWAYS_INLINE DeferTraps::~DeferTraps()
{
    m_traps.m_trapsDeferred = m_previousTrapsDeferred;
}

} // namespace JSC