collector.cpp

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    // FIXME: Consider doing this in NDEBUG builds too (see comment above).
    heap.operationInProgress = NoOperation;
#endif

    return newCell;
}

void* Heap::allocate(size_t s)
{
    return heapAllocate<PrimaryHeap>(s);
}

void* Heap::allocateNumber(size_t s)
{
    return heapAllocate<NumberHeap>(s);
}

static inline void* currentThreadStackBase()
{
#if PLATFORM(DARWIN)
    pthread_t thread = pthread_self();
    return pthread_get_stackaddr_np(thread);
#elif PLATFORM(WIN_OS) && PLATFORM(X86) && COMPILER(MSVC)
    // offset 0x18 from the FS segment register gives a pointer to
    // the thread information block for the current thread
    NT_TIB* pTib;
    __asm {
        MOV EAX, FS:[18h]
        MOV pTib, EAX
    }
    return static_cast<void*>(pTib->StackBase);
#elif PLATFORM(WIN_OS) && PLATFORM(X86_64) && COMPILER(MSVC)
    PNT_TIB64 pTib = reinterpret_cast<PNT_TIB64>(NtCurrentTeb());
    return reinterpret_cast<void*>(pTib->StackBase);
#elif PLATFORM(WIN_OS) && PLATFORM(X86) && COMPILER(GCC)
    // offset 0x18 from the FS segment register gives a pointer to
    // the thread information block for the current thread
    NT_TIB* pTib;
    asm ( "movl %%fs:0x18, %0\n"
          : "=r" (pTib)
        );
    return static_cast<void*>(pTib->StackBase);
#elif PLATFORM(SOLARIS)
    stack_t s;
    thr_stksegment(&s);
    return s.ss_sp;
#elif PLATFORM(OPENBSD)
    pthread_t thread = pthread_self();
    stack_t stack;
    pthread_stackseg_np(thread, &stack);
    return stack.ss_sp;
#elif PLATFORM(UNIX)
    static void* stackBase = 0;
    static size_t stackSize = 0;
    static pthread_t stackThread;
    pthread_t thread = pthread_self();
    if (stackBase == 0 || thread != stackThread) {
        pthread_attr_t sattr;
        pthread_attr_init(&sattr);
#if HAVE(PTHREAD_NP_H) || PLATFORM(NETBSD)
        // e.g. on FreeBSD 5.4, [e-mail]
        pthread_attr_get_np(thread, &sattr);
#else
        // FIXME: this function is non-portable; other POSIX systems may have different np alternatives
        pthread_getattr_np(thread, &sattr);
#endif
        int rc = pthread_attr_getstack(&sattr, &stackBase, &stackSize);
        (void)rc; // FIXME: Deal with error code somehow? Seems fatal.
        ASSERT(stackBase);
        pthread_attr_destroy(&sattr);
        stackThread = thread;
    }
    return static_cast<char*>(stackBase) + stackSize;
#elif PLATFORM(SYMBIAN)
    static void* stackBase = 0;
    if (stackBase == 0) {
        TThreadStackInfo info;
        RThread thread;
        thread.StackInfo(info);
        stackBase = (void*)info.iBase;
    }
    return (void*)stackBase;
#else
#error Need a way to get the stack base on this platform
#endif
}

#if ENABLE(JSC_MULTIPLE_THREADS)

static inline PlatformThread getCurrentPlatformThread()
{
#if PLATFORM(DARWIN)
    return pthread_mach_thread_np(pthread_self());
#elif PLATFORM(WIN_OS)
    HANDLE threadHandle = pthread_getw32threadhandle_np(pthread_self());
    return PlatformThread(GetCurrentThreadId(), threadHandle);
#endif
}

void Heap::makeUsableFromMultipleThreads()
{
    if (m_currentThreadRegistrar)
        return;

    int error = pthread_key_create(&m_currentThreadRegistrar, unregisterThread);
    if (error)
        CRASH();
}

void Heap::registerThread()
{
    if (!m_currentThreadRegistrar || pthread_getspecific(m_currentThreadRegistrar))
        return;

    pthread_setspecific(m_currentThreadRegistrar, this);
    Heap::Thread* thread = new Heap::Thread(pthread_self(), getCurrentPlatformThread(), currentThreadStackBase());

    MutexLocker lock(m_registeredThreadsMutex);

    thread->next = m_registeredThreads;
    m_registeredThreads = thread;
}

void Heap::unregisterThread(void* p)
{
    if (p)
        static_cast<Heap*>(p)->unregisterThread();
}

void Heap::unregisterThread()
{
    pthread_t currentPosixThread = pthread_self();

    MutexLocker lock(m_registeredThreadsMutex);

    if (pthread_equal(currentPosixThread, m_registeredThreads->posixThread)) {
        Thread* t = m_registeredThreads;
        m_registeredThreads = m_registeredThreads->next;
        delete t;
    } else {
        Heap::Thread* last = m_registeredThreads;
        Heap::Thread* t;
        for (t = m_registeredThreads->next; t; t = t->next) {
            if (pthread_equal(t->posixThread, currentPosixThread)) {
                last->next = t->next;
                break;
            }
            last = t;
        }
        ASSERT(t); // If t is NULL, we never found ourselves in the list.
        delete t;
    }
}

#else // ENABLE(JSC_MULTIPLE_THREADS)

void Heap::registerThread()
{
}

#endif

#define IS_POINTER_ALIGNED(p) (((intptr_t)(p) & (sizeof(char*) - 1)) == 0)

// cell size needs to be a power of two for this to be valid
#define IS_HALF_CELL_ALIGNED(p) (((intptr_t)(p) & (CELL_MASK >> 1)) == 0)

void Heap::markConservatively(void* start, void* end)
{
    if (start > end) {
        void* tmp = start;
        start = end;
        end = tmp;
    }

    ASSERT((static_cast<char*>(end) - static_cast<char*>(start)) < 0x1000000);
    ASSERT(IS_POINTER_ALIGNED(start));
    ASSERT(IS_POINTER_ALIGNED(end));

    char** p = static_cast<char**>(start);
    char** e = static_cast<char**>(end);

    size_t usedPrimaryBlocks = primaryHeap.usedBlocks;
    size_t usedNumberBlocks = numberHeap.usedBlocks;
    CollectorBlock** primaryBlocks = primaryHeap.blocks;
    CollectorBlock** numberBlocks = numberHeap.blocks;

    const size_t lastCellOffset = sizeof(CollectorCell) * (CELLS_PER_BLOCK - 1);

    while (p != e) {
        char* x = *p++;
        if (IS_HALF_CELL_ALIGNED(x) && x) {
            uintptr_t xAsBits = reinterpret_cast<uintptr_t>(x);
            xAsBits &= CELL_ALIGN_MASK;
            uintptr_t offset = xAsBits & BLOCK_OFFSET_MASK;
            CollectorBlock* blockAddr = reinterpret_cast<CollectorBlock*>(xAsBits - offset);
            // Mark the the number heap, we can mark these Cells directly to avoid the virtual call cost
            for (size_t block = 0; block < usedNumberBlocks; block++) {
                if ((numberBlocks[block] == blockAddr) & (offset <= lastCellOffset)) {
                    Heap::markCell(reinterpret_cast<JSCell*>(xAsBits));
                    goto endMarkLoop;
                }
            }
          
            // Mark the primary heap
            for (size_t block = 0; block < usedPrimaryBlocks; block++) {
                if ((primaryBlocks[block] == blockAddr) & (offset <= lastCellOffset)) {
                    if (reinterpret_cast<CollectorCell*>(xAsBits)->u.freeCell.zeroIfFree != 0) {
                        JSCell* imp = reinterpret_cast<JSCell*>(xAsBits);
                        if (!imp->marked())
                            imp->mark();
                    }
                    break;
                }
            }
        endMarkLoop:
            ;
        }
    }
}

void NEVER_INLINE Heap::markCurrentThreadConservativelyInternal()
{
    void* dummy;
    void* stackPointer = &dummy;
    void* stackBase = currentThreadStackBase();
    markConservatively(stackPointer, stackBase);
}

void Heap::markCurrentThreadConservatively()
{
    // setjmp forces volatile registers onto the stack
    jmp_buf registers;
#if COMPILER(MSVC)
#pragma warning(push)
#pragma warning(disable: 4611)
#endif
    setjmp(registers);
#if COMPILER(MSVC)
#pragma warning(pop)
#endif

    markCurrentThreadConservativelyInternal();
}

#if ENABLE(JSC_MULTIPLE_THREADS)

static inline void suspendThread(const PlatformThread& platformThread)
{
#if PLATFORM(DARWIN)
    thread_suspend(platformThread);
#elif PLATFORM(WIN_OS)
    SuspendThread(platformThread.handle);
#else
#error Need a way to suspend threads on this platform
#endif
}

static inline void resumeThread(const PlatformThread& platformThread)
{
#if PLATFORM(DARWIN)
    thread_resume(platformThread);
#elif PLATFORM(WIN_OS)
    ResumeThread(platformThread.handle);
#else
#error Need a way to resume threads on this platform
#endif
}

typedef unsigned long usword_t; // word size, assumed to be either 32 or 64 bit

#if PLATFORM(DARWIN)

#if PLATFORM(X86)
typedef i386_thread_state_t PlatformThreadRegisters;
#elif PLATFORM(X86_64)
typedef x86_thread_state64_t PlatformThreadRegisters;
#elif PLATFORM(PPC)
typedef ppc_thread_state_t PlatformThreadRegisters;
#elif PLATFORM(PPC64)
typedef ppc_thread_state64_t PlatformThreadRegisters;
#elif PLATFORM(ARM)
typedef arm_thread_state_t PlatformThreadRegisters;
#else
#error Unknown Architecture
#endif

#elif PLATFORM(WIN_OS)&& PLATFORM(X86)
typedef CONTEXT PlatformThreadRegisters;
#else
#error Need a thread register struct for this platform
#endif

static size_t getPlatformThreadRegisters(const PlatformThread& platformThread, PlatformThreadRegisters& regs)
{
#if PLATFORM(DARWIN)

#if PLATFORM(X86)
    unsigned user_count = sizeof(regs)/sizeof(int);
    thread_state_flavor_t flavor = i386_THREAD_STATE;
#elif PLATFORM(X86_64)
    unsigned user_count = x86_THREAD_STATE64_COUNT;
    thread_state_flavor_t flavor = x86_THREAD_STATE64;
#elif PLATFORM(PPC) 
    unsigned user_count = PPC_THREAD_STATE_COUNT;
    thread_state_flavor_t flavor = PPC_THREAD_STATE;
#elif PLATFORM(PPC64)
    unsigned user_count = PPC_THREAD_STATE64_COUNT;
    thread_state_flavor_t flavor = PPC_THREAD_STATE64;
#elif PLATFORM(ARM)
    unsigned user_count = ARM_THREAD_STATE_COUNT;
    thread_state_flavor_t flavor = ARM_THREAD_STATE;
#else
#error Unknown Architecture
#endif

    kern_return_t result = thread_get_state(platformThread, flavor, (thread_state_t)&regs, &user_count);
    if (result != KERN_SUCCESS) {
        WTFReportFatalError(__FILE__, __LINE__, WTF_PRETTY_FUNCTION, 
                            "JavaScript garbage collection failed because thread_get_state returned an error (%d). This is probably the result of running inside Rosetta, which is not supported.", result);
        CRASH();
    }
    return user_count * sizeof(usword_t);
// end PLATFORM(DARWIN)

#elif PLATFORM(WIN_OS) && PLATFORM(X86)
    regs.ContextFlags = CONTEXT_INTEGER | CONTEXT_CONTROL | CONTEXT_SEGMENTS;
    GetThreadContext(platformThread.handle, &regs);
    return sizeof(CONTEXT);
#else
#error Need a way to get thread registers on this platform
#endif
}

static inline void* otherThreadStackPointer(const PlatformThreadRegisters& regs)
{
#if PLATFORM(DARWIN)

#if __DARWIN_UNIX03

#if PLATFORM(X86)
    return reinterpret_cast<void*>(regs.__esp);
#elif PLATFORM(X86_64)
    return reinterpret_cast<void*>(regs.__rsp);
#elif PLATFORM(PPC) || PLATFORM(PPC64)
    return reinterpret_cast<void*>(regs.__r1);
#elif PLATFORM(ARM)
    return reinterpret_cast<void*>(regs.__sp);
#else
#error Unknown Architecture
#endif

#else // !__DARWIN_UNIX03

#if PLATFORM(X86)
    return reinterpret_cast<void*>(regs.esp);
#elif PLATFORM(X86_64)
    return reinterpret_cast<void*>(regs.rsp);
#elif (PLATFORM(PPC) || PLATFORM(PPC64))
    return reinterpret_cast<void*>(regs.r1);
#else
#error Unknown Architecture
#endif

#endif // __DARWIN_UNIX03

// end PLATFORM(DARWIN)
#elif PLATFORM(X86) && PLATFORM(WIN_OS)
    return reinterpret_cast<void*>((uintptr_t) regs.Esp);
#else
#error Need a way to get the stack pointer for another thread on this platform
#endif
}

void Heap::markOtherThreadConservatively(Thread* thread)