--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/druntime/src/gc/basic/gcx.d	Tue Nov 11 01:52:37 2008 +0100
@@ -0,0 +1,3000 @@
+/**
+ * This module contains the garbage collector implementation.
+ *
+ * Copyright: Copyright (C) 2001-2007 Digital Mars, www.digitalmars.com.
+ *            All rights reserved.
+ * License:
+ *  This software is provided 'as-is', without any express or implied
+ *  warranty. In no event will the authors be held liable for any damages
+ *  arising from the use of this software.
+ *
+ *  Permission is granted to anyone to use this software for any purpose,
+ *  including commercial applications, and to alter it and redistribute it
+ *  freely, in both source and binary form, subject to the following
+ *  restrictions:
+ *
+ *  o  The origin of this software must not be misrepresented; you must not
+ *     claim that you wrote the original software. If you use this software
+ *     in a product, an acknowledgment in the product documentation would be
+ *     appreciated but is not required.
+ *  o  Altered source versions must be plainly marked as such, and must not
+ *     be misrepresented as being the original software.
+ *  o  This notice may not be removed or altered from any source
+ *     distribution.
+ * Authors:   Walter Bright, David Friedman, Sean Kelly
+ */
+
+module gc.gcx;
+
+// D Programming Language Garbage Collector implementation
+
+/************** Debugging ***************************/
+
+//debug = PRINTF;               // turn on printf's
+//debug = COLLECT_PRINTF;       // turn on printf's
+//debug = THREADINVARIANT;      // check thread integrity
+//debug = LOGGING;              // log allocations / frees
+//debug = MEMSTOMP;             // stomp on memory
+//debug = SENTINEL;             // add underrun/overrrun protection
+//debug = PTRCHECK;             // more pointer checking
+//debug = PTRCHECK2;            // thorough but slow pointer checking
+
+/*************** Configuration *********************/
+
+version = STACKGROWSDOWN;       // growing the stack means subtracting from the stack pointer
+                                // (use for Intel X86 CPUs)
+                                // else growing the stack means adding to the stack pointer
+version = MULTI_THREADED;       // produce multithreaded version
+
+/***************************************************/
+
+private import gcbits;
+private import gcstats;
+private import gcalloc;
+
+private import cstdlib = stdc.stdlib : calloc, free, malloc, realloc;
+private import stdc.string;
+
+debug private import stdc.stdio;
+
+version (GNU)
+{
+    // BUG: The following import will likely not work, since the gcc
+    //      subdirectory is elsewhere.  Instead, perhaps the functions
+    //      could be declared directly or some other resolution could
+    //      be found.
+    private import gcc.builtins; // for __builtin_unwind_init
+}
+
+struct BlkInfo
+{
+    void*  base;
+    size_t size;
+    uint   attr;
+}
+
+private
+{
+    enum BlkAttr : uint
+    {
+        FINALIZE = 0b0000_0001,
+        NO_SCAN  = 0b0000_0010,
+        NO_MOVE  = 0b0000_0100,
+        ALL_BITS = 0b1111_1111
+    }
+
+    extern (C) void* rt_stackBottom();
+    extern (C) void* rt_stackTop();
+    extern (C) void* rt_staticDataBottom();
+    extern (C) void* rt_staticDataTop();
+
+    extern (C) void rt_finalize( void* p, bool det = true );
+
+    alias void delegate( void*, void* ) scanFn;
+
+    extern (C) void rt_scanStaticData( scanFn scan );
+
+    version (MULTI_THREADED)
+    {
+        extern (C) bool thread_needLock();
+        extern (C) void thread_suspendAll();
+        extern (C) void thread_resumeAll();
+
+        extern (C) void thread_scanAll( scanFn fn, void* curStackTop = null );
+    }
+
+    extern (C) void onOutOfMemoryError();
+
+    enum
+    {
+        OPFAIL = ~cast(size_t)0
+    }
+}
+
+
+alias GC gc_t;
+
+
+/* ======================= Leak Detector =========================== */
+
+
+debug (LOGGING)
+{
+    struct Log
+    {
+        void*  p;
+        size_t size;
+        size_t line;
+        char*  file;
+        void*  parent;
+
+        void print()
+        {
+            printf("    p = %x, size = %d, parent = %x ", p, size, parent);
+            if (file)
+            {
+                printf("%s(%u)", file, line);
+            }
+            printf("\n");
+        }
+    }
+
+
+    struct LogArray
+    {
+        size_t dim;
+        size_t allocdim;
+        Log *data;
+
+        void Dtor()
+        {
+            if (data)
+                cstdlib.free(data);
+            data = null;
+        }
+
+        void reserve(size_t nentries)
+        {
+            assert(dim <= allocdim);
+            if (allocdim - dim < nentries)
+            {
+                allocdim = (dim + nentries) * 2;
+                assert(dim + nentries <= allocdim);
+                if (!data)
+                {
+                    data = cast(Log*)cstdlib.malloc(allocdim * Log.sizeof);
+                    if (!data && allocdim)
+                        onOutOfMemoryError();
+                }
+                else
+                {   Log *newdata;
+
+                    newdata = cast(Log*)cstdlib.malloc(allocdim * Log.sizeof);
+                    if (!newdata && allocdim)
+                        onOutOfMemoryError();
+                    memcpy(newdata, data, dim * Log.sizeof);
+                    cstdlib.free(data);
+                    data = newdata;
+                }
+            }
+        }
+
+
+        void push(Log log)
+        {
+            reserve(1);
+            data[dim++] = log;
+        }
+
+        void remove(size_t i)
+        {
+            memmove(data + i, data + i + 1, (dim - i) * Log.sizeof);
+            dim--;
+        }
+
+
+        size_t find(void *p)
+        {
+            for (size_t i = 0; i < dim; i++)
+            {
+                if (data[i].p == p)
+                    return i;
+            }
+            return OPFAIL; // not found
+        }
+
+
+        void copy(LogArray *from)
+        {
+            reserve(from.dim - dim);
+            assert(from.dim <= allocdim);
+            memcpy(data, from.data, from.dim * Log.sizeof);
+            dim = from.dim;
+        }
+    }
+}
+
+
+/* ============================ GC =============================== */
+
+
+class GCLock { }                // just a dummy so we can get a global lock
+
+
+const uint GCVERSION = 1;       // increment every time we change interface
+                                // to GC.
+
+class GC
+{
+    // For passing to debug code
+    static size_t line;
+    static char*  file;
+
+    uint gcversion = GCVERSION;
+
+    Gcx *gcx;                   // implementation
+    static ClassInfo gcLock;    // global lock
+
+
+    void initialize()
+    {
+        gcLock = GCLock.classinfo;
+        gcx = cast(Gcx*)cstdlib.calloc(1, Gcx.sizeof);
+        if (!gcx)
+            onOutOfMemoryError();
+        gcx.initialize();
+        setStackBottom(rt_stackBottom());
+    }
+
+
+    void Dtor()
+    {
+        version (linux)
+        {
+            //debug(PRINTF) printf("Thread %x ", pthread_self());
+            //debug(PRINTF) printf("GC.Dtor()\n");
+        }
+
+        if (gcx)
+        {
+            gcx.Dtor();
+            cstdlib.free(gcx);
+            gcx = null;
+        }
+    }
+
+
+    invariant()
+    {
+        if (gcx)
+        {
+            gcx.thread_Invariant();
+        }
+    }
+
+
+    /**
+     *
+     */
+    void enable()
+    {
+        if (!thread_needLock())
+        {
+            assert(gcx.disabled > 0);
+            gcx.disabled--;
+        }
+        else synchronized (gcLock)
+        {
+            assert(gcx.disabled > 0);
+            gcx.disabled--;
+        }
+    }
+
+
+    /**
+     *
+     */
+    void disable()
+    {
+        if (!thread_needLock())
+        {
+            gcx.disabled++;
+        }
+        else synchronized (gcLock)
+        {
+            gcx.disabled++;
+        }
+    }
+
+
+    /**
+     *
+     */
+    uint getAttr(void* p)
+    {
+        if (!p)
+        {
+            return 0;
+        }
+
+        uint go()
+        {
+            Pool* pool = gcx.findPool(p);
+            uint  oldb = 0;
+
+            if (pool)
+            {
+                auto biti = cast(size_t)(p - pool.baseAddr) / 16;
+
+                oldb = gcx.getBits(pool, biti);
+            }
+            return oldb;
+        }
+
+        if (!thread_needLock())
+        {
+            return go();
+        }
+        else synchronized (gcLock)
+        {
+            return go();
+        }
+    }
+
+
+    /**
+     *
+     */
+    uint setAttr(void* p, uint mask)
+    {
+        if (!p)
+        {
+            return 0;
+        }
+
+        uint go()
+        {
+            Pool* pool = gcx.findPool(p);
+            uint  oldb = 0;
+
+            if (pool)
+            {
+                auto biti = cast(size_t)(p - pool.baseAddr) / 16;
+
+                oldb = gcx.getBits(pool, biti);
+                gcx.setBits(pool, biti, mask);
+            }
+            return oldb;
+        }
+
+        if (!thread_needLock())
+        {
+            return go();
+        }
+        else synchronized (gcLock)
+        {
+            return go();
+        }
+    }
+
+
+    /**
+     *
+     */
+    uint clrAttr(void* p, uint mask)
+    {
+        if (!p)
+        {
+            return 0;
+        }
+
+        uint go()
+        {
+            Pool* pool = gcx.findPool(p);
+            uint  oldb = 0;
+
+            if (pool)
+            {
+                auto biti = cast(size_t)(p - pool.baseAddr) / 16;
+
+                oldb = gcx.getBits(pool, biti);
+                gcx.clrBits(pool, biti, mask);
+            }
+            return oldb;
+        }
+
+        if (!thread_needLock())
+        {
+            return go();
+        }
+        else synchronized (gcLock)
+        {
+            return go();
+        }
+    }
+
+
+    /**
+     *
+     */
+    void *malloc(size_t size, uint bits = 0)
+    {
+        if (!size)
+        {
+            return null;
+        }
+
+        if (!thread_needLock())
+        {
+            return mallocNoSync(size, bits);
+        }
+        else synchronized (gcLock)
+        {
+            return mallocNoSync(size, bits);
+        }
+    }
+
+
+    //
+    //
+    //
+    private void *mallocNoSync(size_t size, uint bits = 0)
+    {
+        assert(size != 0);
+
+        void *p = null;
+        Bins bin;
+
+        //debug(PRINTF) printf("GC::malloc(size = %d, gcx = %p)\n", size, gcx);
+        assert(gcx);
+        //debug(PRINTF) printf("gcx.self = %x, pthread_self() = %x\n", gcx.self, pthread_self());
+
+        size += SENTINEL_EXTRA;
+
+        // Compute size bin
+        // Cache previous binsize lookup - Dave Fladebo.
+        static size_t lastsize = -1;
+        static Bins lastbin;
+        if (size == lastsize)
+            bin = lastbin;
+        else
+        {
+            bin = gcx.findBin(size);
+            lastsize = size;
+            lastbin = bin;
+        }
+
+        if (bin < B_PAGE)
+        {
+            p = gcx.bucket[bin];
+            if (p is null)
+            {
+                if (!gcx.allocPage(bin) && !gcx.disabled)   // try to find a new page
+                {
+                    if (!thread_needLock())
+                    {
+                        /* Then we haven't locked it yet. Be sure
+                         * and lock for a collection, since a finalizer
+                         * may start a new thread.
+                         */
+                        synchronized (gcLock)
+                        {
+                            gcx.fullcollectshell();
+                        }
+                    }
+                    else if (!gcx.fullcollectshell())       // collect to find a new page
+                    {
+                        //gcx.newPool(1);
+                    }
+                }
+                if (!gcx.bucket[bin] && !gcx.allocPage(bin))
+                {   int result;
+
+                    gcx.newPool(1);         // allocate new pool to find a new page
+                    result = gcx.allocPage(bin);
+                    if (!result)
+                        onOutOfMemoryError();
+                }
+                p = gcx.bucket[bin];
+            }
+
+            // Return next item from free list
+            gcx.bucket[bin] = (cast(List*)p).next;
+            if( !(bits & BlkAttr.NO_SCAN) )
+                memset(p + size, 0, binsize[bin] - size);
+            //debug(PRINTF) printf("\tmalloc => %x\n", p);
+            debug (MEMSTOMP) memset(p, 0xF0, size);
+        }
+        else
+        {
+            p = gcx.bigAlloc(size);
+            if (!p)
+                onOutOfMemoryError();
+        }
+        size -= SENTINEL_EXTRA;
+        p = sentinel_add(p);
+        sentinel_init(p, size);
+        gcx.log_malloc(p, size);
+
+        if (bits)
+        {
+            Pool *pool = gcx.findPool(p);
+            assert(pool);
+
+            gcx.setBits(pool, cast(size_t)(p - pool.baseAddr) / 16, bits);
+        }
+        return p;
+    }
+
+
+    /**
+     *
+     */
+    void *calloc(size_t size, uint bits = 0)
+    {
+        if (!size)
+        {
+            return null;
+        }
+
+        if (!thread_needLock())
+        {
+            return callocNoSync(size, bits);
+        }
+        else synchronized (gcLock)
+        {
+            return callocNoSync(size, bits);
+        }
+    }
+
+
+    //
+    //
+    //
+    private void *callocNoSync(size_t size, uint bits = 0)
+    {
+        assert(size != 0);
+
+        //debug(PRINTF) printf("calloc: %x len %d\n", p, len);
+        void *p = mallocNoSync(size, bits);
+        memset(p, 0, size);
+        return p;
+    }
+
+
+    /**
+     *
+     */
+    void *realloc(void *p, size_t size, uint bits = 0)
+    {
+        if (!thread_needLock())
+        {
+            return reallocNoSync(p, size, bits);
+        }
+        else synchronized (gcLock)
+        {
+            return reallocNoSync(p, size, bits);
+        }
+    }
+
+
+    //
+    //
+    //
+    private void *reallocNoSync(void *p, size_t size, uint bits = 0)
+    {
+        if (!size)
+        {   if (p)
+            {   freeNoSync(p);
+                p = null;
+            }
+        }
+        else if (!p)
+        {
+            p = mallocNoSync(size, bits);
+        }
+        else
+        {   void *p2;
+            size_t psize;
+
+            //debug(PRINTF) printf("GC::realloc(p = %x, size = %u)\n", p, size);
+            version (SENTINEL)
+            {
+                sentinel_Invariant(p);
+                psize = *sentinel_size(p);
+                if (psize != size)
+                {
+                    if (psize)
+                    {
+                        Pool *pool = gcx.findPool(p);
+
+                        if (pool)
+                        {
+                            auto biti = cast(size_t)(p - pool.baseAddr) / 16;
+
+                            if (bits)
+                            {
+                                gcx.clrBits(pool, biti, BlkAttr.ALL_BITS);
+                                gcx.setBits(pool, biti, bits);
+                            }
+                            else
+                            {
+                                bits = gcx.getBits(pool, biti);
+                            }
+                        }
+                    }
+                    p2 = mallocNoSync(size, bits);
+                    if (psize < size)
+                        size = psize;
+                    //debug(PRINTF) printf("\tcopying %d bytes\n",size);
+                    memcpy(p2, p, size);
+                    p = p2;
+                }
+            }
+            else
+            {
+                psize = gcx.findSize(p);        // find allocated size
+                if (psize >= PAGESIZE && size >= PAGESIZE)
+                {
+                    auto psz = psize / PAGESIZE;
+                    auto newsz = (size + PAGESIZE - 1) / PAGESIZE;
+                    if (newsz == psz)
+                        return p;
+
+                    auto pool = gcx.findPool(p);
+                    auto pagenum = (p - pool.baseAddr) / PAGESIZE;
+
+                    if (newsz < psz)
+                    {   // Shrink in place
+                        synchronized (gcLock)
+                        {
+                            debug (MEMSTOMP) memset(p + size, 0xF2, psize - size);
+                            pool.freePages(pagenum + newsz, psz - newsz);
+                        }
+                        return p;
+                    }
+                    else if (pagenum + newsz <= pool.npages)
+                    {
+                        // Attempt to expand in place
+                        synchronized (gcLock)
+                        {
+                            for (size_t i = pagenum + psz; 1;)
+                            {
+                                if (i == pagenum + newsz)
+                                {
+                                    debug (MEMSTOMP) memset(p + psize, 0xF0, size - psize);
+                                    memset(&pool.pagetable[pagenum + psz], B_PAGEPLUS, newsz - psz);
+                                    return p;
+                                }
+                                if (i == pool.ncommitted)
+                                {
+                                    auto u = pool.extendPages(pagenum + newsz - pool.ncommitted);
+                                    if (u == OPFAIL)
+                                        break;
+                                    i = pagenum + newsz;
+                                    continue;
+                                }
+                                if (pool.pagetable[i] != B_FREE)
+                                    break;
+                                i++;
+                            }
+                        }
+                    }
+                }
+                if (psize < size ||             // if new size is bigger
+                    psize > size * 2)           // or less than half
+                {
+                    if (psize)
+                    {
+                        Pool *pool = gcx.findPool(p);
+
+                        if (pool)
+                        {
+                            auto biti = cast(size_t)(p - pool.baseAddr) / 16;
+
+                            if (bits)
+                            {
+                                gcx.clrBits(pool, biti, BlkAttr.ALL_BITS);
+                                gcx.setBits(pool, biti, bits);
+                            }
+                            else
+                            {
+                                bits = gcx.getBits(pool, biti);
+                            }
+                        }
+                    }
+                    p2 = mallocNoSync(size, bits);
+                    if (psize < size)
+                        size = psize;
+                    //debug(PRINTF) printf("\tcopying %d bytes\n",size);
+                    memcpy(p2, p, size);
+                    p = p2;
+                }
+            }
+        }
+        return p;
+    }
+
+
+    /**
+     * Attempt to in-place enlarge the memory block pointed to by p by at least
+     * minbytes beyond its current capacity, up to a maximum of maxsize.  This
+     * does not attempt to move the memory block (like realloc() does).
+     *
+     * Returns:
+     *  0 if could not extend p,
+     *  total size of entire memory block if successful.
+     */
+    size_t extend(void* p, size_t minsize, size_t maxsize)
+    {
+        if (!thread_needLock())
+        {
+            return extendNoSync(p, minsize, maxsize);
+        }
+        else synchronized (gcLock)
+        {
+            return extendNoSync(p, minsize, maxsize);
+        }
+    }
+
+
+    //
+    //
+    //
+    private size_t extendNoSync(void* p, size_t minsize, size_t maxsize)
+    in
+    {
+        assert( minsize <= maxsize );
+    }
+    body
+    {
+        //debug(PRINTF) printf("GC::extend(p = %x, minsize = %u, maxsize = %u)\n", p, minsize, maxsize);
+        version (SENTINEL)
+        {
+            return 0;
+        }
+        auto psize = gcx.findSize(p);   // find allocated size
+        if (psize < PAGESIZE)
+            return 0;                   // cannot extend buckets
+
+        auto psz = psize / PAGESIZE;
+        auto minsz = (minsize + PAGESIZE - 1) / PAGESIZE;
+        auto maxsz = (maxsize + PAGESIZE - 1) / PAGESIZE;
+
+        auto pool = gcx.findPool(p);
+        auto pagenum = (p - pool.baseAddr) / PAGESIZE;
+
+        size_t sz;
+        for (sz = 0; sz < maxsz; sz++)
+        {
+            auto i = pagenum + psz + sz;
+            if (i == pool.ncommitted)
+                break;
+            if (pool.pagetable[i] != B_FREE)
+            {   if (sz < minsz)
+                    return 0;
+                break;
+            }
+        }
+        if (sz >= minsz)
+        {
+        }
+        else if (pagenum + psz + sz == pool.ncommitted)
+        {
+            auto u = pool.extendPages(minsz - sz);
+            if (u == OPFAIL)
+                return 0;
+            sz = minsz;
+        }
+        else
+            return 0;
+        debug (MEMSTOMP) memset(p + psize, 0xF0, (psz + sz) * PAGESIZE - psize);
+        memset(pool.pagetable + pagenum + psz, B_PAGEPLUS, sz);
+        gcx.p_cache = null;
+        gcx.size_cache = 0;
+        return (psz + sz) * PAGESIZE;
+    }
+
+
+    /**
+     *
+     */
+    size_t reserve(size_t size)
+    {
+        if (!size)
+        {
+            return 0;
+        }
+
+        if (!thread_needLock())
+        {
+            return reserveNoSync(size);
+        }
+        else synchronized (gcLock)
+        {
+            return reserveNoSync(size);
+        }
+    }
+
+
+    //
+    //
+    //
+    private size_t reserveNoSync(size_t size)
+    {
+        assert(size != 0);
+        assert(gcx);
+
+        return gcx.reserve(size);
+    }
+
+
+    /**
+     *
+     */
+    void free(void *p)
+    {
+        if (!p)
+        {
+            return;
+        }
+
+        if (!thread_needLock())
+        {
+            return freeNoSync(p);
+        }
+        else synchronized (gcLock)
+        {
+            return freeNoSync(p);
+        }
+    }
+
+
+    //
+    //
+    //
+    private void freeNoSync(void *p)
+    {
+        assert (p);
+
+        Pool*  pool;
+        size_t pagenum;
+        Bins   bin;
+        size_t biti;
+
+        // Find which page it is in
+        pool = gcx.findPool(p);
+        if (!pool)                              // if not one of ours
+            return;                             // ignore
+        sentinel_Invariant(p);
+        p = sentinel_sub(p);
+        pagenum = cast(size_t)(p - pool.baseAddr) / PAGESIZE;
+        biti = cast(size_t)(p - pool.baseAddr) / 16;
+        gcx.clrBits(pool, biti, BlkAttr.ALL_BITS);
+
+        bin = cast(Bins)pool.pagetable[pagenum];
+        if (bin == B_PAGE)              // if large alloc
+        {   size_t npages;
+            size_t n;
+
+            // Free pages
+            npages = 1;
+            n = pagenum;
+            while (++n < pool.ncommitted && pool.pagetable[n] == B_PAGEPLUS)
+                npages++;
+            debug (MEMSTOMP) memset(p, 0xF2, npages * PAGESIZE);
+            pool.freePages(pagenum, npages);
+        }
+        else
+        {   // Add to free list
+            List *list = cast(List*)p;
+
+            debug (MEMSTOMP) memset(p, 0xF2, binsize[bin]);
+
+            list.next = gcx.bucket[bin];
+            gcx.bucket[bin] = list;
+        }
+        gcx.log_free(sentinel_add(p));
+    }
+
+
+    /**
+     * Determine the base address of the block containing p.  If p is not a gc
+     * allocated pointer, return null.
+     */
+    void* addrOf(void *p)
+    {
+        if (!p)
+        {
+            return null;
+        }
+
+        if (!thread_needLock())
+        {
+            return addrOfNoSync(p);
+        }
+        else synchronized (gcLock)
+        {
+            return addrOfNoSync(p);
+        }
+    }
+
+
+    //
+    //
+    //
+    void* addrOfNoSync(void *p)
+    {
+        if (!p)
+        {
+            return null;
+        }
+
+        return gcx.findBase(p);
+    }
+
+
+    /**
+     * Determine the allocated size of pointer p.  If p is an interior pointer
+     * or not a gc allocated pointer, return 0.
+     */
+    size_t sizeOf(void *p)
+    {
+        if (!p)
+        {
+            return 0;
+        }
+
+        if (!thread_needLock())
+        {
+            return sizeOfNoSync(p);
+        }
+        else synchronized (gcLock)
+        {
+            return sizeOfNoSync(p);
+        }
+    }
+
+
+    //
+    //
+    //
+    private size_t sizeOfNoSync(void *p)
+    {
+        assert (p);
+
+        version (SENTINEL)
+        {
+            p = sentinel_sub(p);
+            size_t size = gcx.findSize(p);
+
+            // Check for interior pointer
+            // This depends on:
+            // 1) size is a power of 2 for less than PAGESIZE values
+            // 2) base of memory pool is aligned on PAGESIZE boundary
+            if (cast(size_t)p & (size - 1) & (PAGESIZE - 1))
+                size = 0;
+            return size ? size - SENTINEL_EXTRA : 0;
+        }
+        else
+        {
+            if (p == gcx.p_cache)
+                return gcx.size_cache;
+
+            size_t size = gcx.findSize(p);
+
+            // Check for interior pointer
+            // This depends on:
+            // 1) size is a power of 2 for less than PAGESIZE values
+            // 2) base of memory pool is aligned on PAGESIZE boundary
+            if (cast(size_t)p & (size - 1) & (PAGESIZE - 1))
+                size = 0;
+            else
+            {
+                gcx.p_cache = p;
+                gcx.size_cache = size;
+            }
+
+            return size;
+        }
+    }
+
+
+    /**
+     * Determine the base address of the block containing p.  If p is not a gc
+     * allocated pointer, return null.
+     */
+    BlkInfo query(void *p)
+    {
+        if (!p)
+        {
+            BlkInfo i;
+            return  i;
+        }
+
+        if (!thread_needLock())
+        {
+            return queryNoSync(p);
+        }
+        else synchronized (gcLock)
+        {
+            return queryNoSync(p);
+        }
+    }
+
+
+    //
+    //
+    //
+    BlkInfo queryNoSync(void *p)
+    {
+        assert(p);
+
+        return gcx.getInfo(p);
+    }
+
+
+    /**
+     * Verify that pointer p:
+     *  1) belongs to this memory pool
+     *  2) points to the start of an allocated piece of memory
+     *  3) is not on a free list
+     */
+    void check(void *p)
+    {
+        if (!p)
+        {
+            return;
+        }
+
+        if (!thread_needLock())
+        {
+            checkNoSync(p);
+        }
+        else synchronized (gcLock)
+        {
+            checkNoSync(p);
+        }
+    }
+
+
+    //
+    //
+    //
+    private void checkNoSync(void *p)
+    {
+        assert(p);
+
+        sentinel_Invariant(p);
+        debug (PTRCHECK)
+        {
+            Pool*  pool;
+            size_t pagenum;
+            Bins   bin;
+            size_t size;
+
+            p = sentinel_sub(p);
+            pool = gcx.findPool(p);
+            assert(pool);
+            pagenum = cast(size_t)(p - pool.baseAddr) / PAGESIZE;
+            bin = cast(Bins)pool.pagetable[pagenum];
+            assert(bin <= B_PAGE);
+            size = binsize[bin];
+            assert((cast(size_t)p & (size - 1)) == 0);
+
+            debug (PTRCHECK2)
+            {
+                if (bin < B_PAGE)
+                {
+                    // Check that p is not on a free list
+                    List *list;
+
+                    for (list = gcx.bucket[bin]; list; list = list.next)
+                    {
+                        assert(cast(void*)list != p);
+                    }
+                }
+            }
+        }
+    }
+
+
+    //
+    //
+    //
+    private void setStackBottom(void *p)
+    {
+        version (STACKGROWSDOWN)
+        {
+            //p = (void *)((uint *)p + 4);
+            if (p > gcx.stackBottom)
+            {
+                //debug(PRINTF) printf("setStackBottom(%x)\n", p);
+                gcx.stackBottom = p;
+            }
+        }
+        else
+        {
+            //p = (void *)((uint *)p - 4);
+            if (p < gcx.stackBottom)
+            {
+                //debug(PRINTF) printf("setStackBottom(%x)\n", p);
+                gcx.stackBottom = cast(char*)p;
+            }
+        }
+    }
+
+
+    static void scanStaticData(gc_t g)
+    {
+        //debug(PRINTF) printf("+GC.scanStaticData()\n");
+        auto pbot = rt_staticDataBottom();
+        auto ptop = rt_staticDataTop();
+        g.addRange(pbot, ptop - pbot);
+        //debug(PRINTF) printf("-GC.scanStaticData()\n");
+    }
+
+    static void unscanStaticData(gc_t g)
+    {
+        auto pbot = rt_staticDataBottom();
+        g.removeRange(pbot);
+    }
+
+    /**
+     * add p to list of roots
+     */
+    void addRoot(void *p)
+    {
+        if (!p)
+        {
+            return;
+        }
+
+        if (!thread_needLock())
+        {
+            gcx.addRoot(p);
+        }
+        else synchronized (gcLock)
+        {
+            gcx.addRoot(p);
+        }
+    }
+
+
+    /**
+     * remove p from list of roots
+     */
+    void removeRoot(void *p)
+    {
+        if (!p)
+        {
+            return;
+        }
+
+        if (!thread_needLock())
+        {
+            gcx.removeRoot(p);
+        }
+        else synchronized (gcLock)
+        {
+            gcx.removeRoot(p);
+        }
+    }
+
+
+    /**
+     * add range to scan for roots
+     */
+    void addRange(void *p, size_t sz)
+    {
+        if (!p || !sz)
+        {
+            return;
+        }
+
+        //debug(PRINTF) printf("+GC.addRange(pbot = x%x, ptop = x%x)\n", pbot, ptop);
+        if (!thread_needLock())
+        {
+            gcx.addRange(p, p + sz);
+        }
+        else synchronized (gcLock)
+        {
+            gcx.addRange(p, p + sz);
+        }
+        //debug(PRINTF) printf("-GC.addRange()\n");
+    }
+
+
+    /**
+     * remove range
+     */
+    void removeRange(void *p)
+    {
+        if (!p)
+        {
+            return;
+        }
+
+        if (!thread_needLock())
+        {
+            gcx.removeRange(p);
+        }
+        else synchronized (gcLock)
+        {
+            gcx.removeRange(p);
+        }
+    }
+
+
+    /**
+     * do full garbage collection
+     */
+    void fullCollect()
+    {
+        debug(PRINTF) printf("GC.fullCollect()\n");
+
+        if (!thread_needLock())
+        {
+            gcx.fullcollectshell();
+        }
+        else synchronized (gcLock)
+        {
+            gcx.fullcollectshell();
+        }
+
+        version (none)
+        {
+            GCStats stats;
+
+            getStats(stats);
+            debug(PRINTF) printf("poolsize = %x, usedsize = %x, freelistsize = %x\n",
+                    stats.poolsize, stats.usedsize, stats.freelistsize);
+        }
+
+        gcx.log_collect();
+    }
+
+
+    /**
+     * do full garbage collection ignoring roots
+     */
+    void fullCollectNoStack()
+    {
+        if (!thread_needLock())
+        {
+            gcx.noStack++;
+            gcx.fullcollectshell();
+            gcx.noStack--;
+        }
+        else synchronized (gcLock)
+        {
+            gcx.noStack++;
+            gcx.fullcollectshell();
+            gcx.noStack--;
+        }
+    }
+
+
+    /**
+     * minimize free space usage
+     */
+    void minimize()
+    {
+        if (!thread_needLock())
+        {
+            gcx.minimize();
+        }
+        else synchronized (gcLock)
+        {
+            gcx.minimize();
+        }
+    }
+
+
+    /**
+     * Retrieve statistics about garbage collection.
+     * Useful for debugging and tuning.
+     */
+    void getStats(out GCStats stats)
+    {
+        if (!thread_needLock())
+        {
+            getStatsNoSync(stats);
+        }
+        else synchronized (gcLock)
+        {
+            getStatsNoSync(stats);
+        }
+    }
+
+
+    //
+    //
+    //
+    private void getStatsNoSync(out GCStats stats)
+    {
+        size_t psize = 0;
+        size_t usize = 0;
+        size_t flsize = 0;
+
+        size_t n;
+        size_t bsize = 0;
+
+        //debug(PRINTF) printf("getStats()\n");
+        memset(&stats, 0, GCStats.sizeof);
+
+        for (n = 0; n < gcx.npools; n++)
+        {   Pool *pool = gcx.pooltable[n];
+
+            psize += pool.ncommitted * PAGESIZE;
+            for (size_t j = 0; j < pool.ncommitted; j++)
+            {
+                Bins bin = cast(Bins)pool.pagetable[j];
+                if (bin == B_FREE)
+                    stats.freeblocks++;
+                else if (bin == B_PAGE)
+                    stats.pageblocks++;
+                else if (bin < B_PAGE)
+                    bsize += PAGESIZE;
+            }
+        }
+
+        for (n = 0; n < B_PAGE; n++)
+        {
+            //debug(PRINTF) printf("bin %d\n", n);
+            for (List *list = gcx.bucket[n]; list; list = list.next)
+            {
+                //debug(PRINTF) printf("\tlist %x\n", list);
+                flsize += binsize[n];
+            }
+        }
+
+        usize = bsize - flsize;
+
+        stats.poolsize = psize;
+        stats.usedsize = bsize - flsize;
+        stats.freelistsize = flsize;
+    }
+}
+
+
+/* ============================ Gcx =============================== */
+
+enum
+{   PAGESIZE =    4096,
+    COMMITSIZE = (4096*16),
+    POOLSIZE =   (4096*256),
+}
+
+
+enum
+{
+    B_16,
+    B_32,
+    B_64,
+    B_128,
+    B_256,
+    B_512,
+    B_1024,
+    B_2048,
+    B_PAGE,             // start of large alloc
+    B_PAGEPLUS,         // continuation of large alloc
+    B_FREE,             // free page
+    B_UNCOMMITTED,      // memory not committed for this page
+    B_MAX
+}
+
+
+alias ubyte Bins;
+
+
+struct List
+{
+    List *next;
+}
+
+
+struct Range
+{
+    void *pbot;
+    void *ptop;
+}
+
+
+const uint binsize[B_MAX] = [ 16,32,64,128,256,512,1024,2048,4096 ];
+const uint notbinsize[B_MAX] = [ ~(16u-1),~(32u-1),~(64u-1),~(128u-1),~(256u-1),
+                                ~(512u-1),~(1024u-1),~(2048u-1),~(4096u-1) ];
+
+/* ============================ Gcx =============================== */
+
+
+struct Gcx
+{
+    debug (THREADINVARIANT)
+    {
+        pthread_t self;
+        void thread_Invariant()
+        {
+            if (self != pthread_self())
+                printf("thread_Invariant(): gcx = %x, self = %x, pthread_self() = %x\n", this, self, pthread_self());
+            assert(self == pthread_self());
+        }
+    }
+    else
+    {
+        void thread_Invariant() { }
+    }
+
+    void *p_cache;
+    size_t size_cache;
+
+    size_t nroots;
+    size_t rootdim;
+    void **roots;
+
+    size_t nranges;
+    size_t rangedim;
+    Range *ranges;
+
+    uint noStack;       // !=0 means don't scan stack
+    uint log;           // turn on logging
+    uint anychanges;
+    void *stackBottom;
+    uint inited;
+    int disabled;       // turn off collections if >0
+
+    byte *minAddr;      // min(baseAddr)
+    byte *maxAddr;      // max(topAddr)
+
+    size_t npools;
+    Pool **pooltable;
+
+    List *bucket[B_MAX];        // free list for each size
+
+
+    void initialize()
+    {   int dummy;
+
+        (cast(byte*)this)[0 .. Gcx.sizeof] = 0;
+        stackBottom = cast(char*)&dummy;
+        log_init();
+        debug (THREADINVARIANT)
+            self = pthread_self();
+        //printf("gcx = %p, self = %x\n", this, self);
+        inited = 1;
+    }
+
+
+    void Dtor()
+    {
+        inited = 0;
+
+        for (size_t i = 0; i < npools; i++)
+        {   Pool *pool = pooltable[i];
+
+            pool.Dtor();
+            cstdlib.free(pool);
+        }
+        if (pooltable)
+            cstdlib.free(pooltable);
+
+        if (roots)
+            cstdlib.free(roots);
+
+        if (ranges)
+            cstdlib.free(ranges);
+    }
+
+
+    void Invariant() { }
+
+
+    invariant()
+    {
+        if (inited)
+        {
+        //printf("Gcx.invariant(): this = %p\n", this);
+            size_t i;
+
+            // Assure we're called on the right thread
+            debug (THREADINVARIANT) assert(self == pthread_self());
+
+            for (i = 0; i < npools; i++)
+            {   Pool *pool = pooltable[i];
+
+                pool.Invariant();
+                if (i == 0)
+                {
+                    assert(minAddr == pool.baseAddr);
+                }
+                if (i + 1 < npools)
+                {
+                    assert(pool.opCmp(pooltable[i + 1]) < 0);
+                }
+                else if (i + 1 == npools)
+                {
+                    assert(maxAddr == pool.topAddr);
+                }
+            }
+
+            if (roots)
+            {
+                assert(rootdim != 0);
+                assert(nroots <= rootdim);
+            }
+
+            if (ranges)
+            {
+                assert(rangedim != 0);
+                assert(nranges <= rangedim);
+
+                for (i = 0; i < nranges; i++)
+                {
+                    assert(ranges[i].pbot);
+                    assert(ranges[i].ptop);
+                    assert(ranges[i].pbot <= ranges[i].ptop);
+                }
+            }
+
+            for (i = 0; i < B_PAGE; i++)
+            {
+                for (List *list = bucket[i]; list; list = list.next)
+                {
+                }
+            }
+        }
+    }
+
+
+    /**
+     *
+     */
+    void addRoot(void *p)
+    {
+        if (nroots == rootdim)
+        {
+            size_t newdim = rootdim * 2 + 16;
+            void** newroots;
+
+            newroots = cast(void**)cstdlib.malloc(newdim * newroots[0].sizeof);
+            if (!newroots)
+                onOutOfMemoryError();
+            if (roots)
+            {   memcpy(newroots, roots, nroots * newroots[0].sizeof);
+                cstdlib.free(roots);
+            }
+            roots = newroots;
+            rootdim = newdim;
+        }
+        roots[nroots] = p;
+        nroots++;
+    }
+
+
+    /**
+     *
+     */
+    void removeRoot(void *p)
+    {
+        for (size_t i = nroots; i--;)
+        {
+            if (roots[i] == p)
+            {
+                nroots--;
+                memmove(roots + i, roots + i + 1, (nroots - i) * roots[0].sizeof);
+                return;
+            }
+        }
+        assert(0);
+    }
+
+
+    /**
+     *
+     */
+    void addRange(void *pbot, void *ptop)
+    {
+        debug(PRINTF) printf("Thread %x ", pthread_self());
+        debug(PRINTF) printf("%x.Gcx::addRange(%x, %x), nranges = %d\n", this, pbot, ptop, nranges);
+        if (nranges == rangedim)
+        {
+            size_t newdim = rangedim * 2 + 16;
+            Range *newranges;
+
+            newranges = cast(Range*)cstdlib.malloc(newdim * newranges[0].sizeof);
+            if (!newranges)
+                onOutOfMemoryError();
+            if (ranges)
+            {   memcpy(newranges, ranges, nranges * newranges[0].sizeof);
+                cstdlib.free(ranges);
+            }
+            ranges = newranges;
+            rangedim = newdim;
+        }
+        ranges[nranges].pbot = pbot;
+        ranges[nranges].ptop = ptop;
+        nranges++;
+    }
+
+
+    /**
+     *
+     */
+    void removeRange(void *pbot)
+    {
+        debug(PRINTF) printf("Thread %x ", pthread_self());
+        debug(PRINTF) printf("%x.Gcx.removeRange(%x), nranges = %d\n", this, pbot, nranges);
+        for (size_t i = nranges; i--;)
+        {
+            if (ranges[i].pbot == pbot)
+            {
+                nranges--;
+                memmove(ranges + i, ranges + i + 1, (nranges - i) * ranges[0].sizeof);
+                return;
+            }
+        }
+        debug(PRINTF) printf("Wrong thread\n");
+
+        // This is a fatal error, but ignore it.
+        // The problem is that we can get a Close() call on a thread
+        // other than the one the range was allocated on.
+        //assert(zero);
+    }
+
+
+    /**
+     * Find Pool that pointer is in.
+     * Return null if not in a Pool.
+     * Assume pooltable[] is sorted.
+     */
+    Pool *findPool(void *p)
+    {
+        if (p >= minAddr && p < maxAddr)
+        {
+            if (npools == 1)
+            {
+                return pooltable[0];
+            }
+
+            for (size_t i = 0; i < npools; i++)
+            {   Pool *pool;
+
+                pool = pooltable[i];
+                if (p < pool.topAddr)
+                {   if (pool.baseAddr <= p)
+                        return pool;
+                    break;
+                }
+            }
+        }
+        return null;
+    }
+
+
+    /**
+     * Find base address of block containing pointer p.
+     * Returns null if not a gc'd pointer
+     */
+    void* findBase(void *p)
+    {
+        Pool *pool;
+
+        pool = findPool(p);
+        if (pool)
+        {
+            size_t offset = cast(size_t)(p - pool.baseAddr);
+            size_t pn = offset / PAGESIZE;
+            Bins   bin = cast(Bins)pool.pagetable[pn];
+
+            // Adjust bit to be at start of allocated memory block
+            if (bin <= B_PAGE)
+            {
+                return pool.baseAddr + (offset & notbinsize[bin]);
+            }
+            else if (bin == B_PAGEPLUS)
+            {
+                do
+                {   --pn, offset -= PAGESIZE;
+                } while (cast(Bins)pool.pagetable[pn] == B_PAGEPLUS);
+
+                return pool.baseAddr + (offset & (offset.max ^ (PAGESIZE-1)));
+            }
+            else
+            {
+                // we are in a B_FREE or B_UNCOMMITTED page
+                return null;
+            }
+        }
+        return null;
+    }
+
+
+    /**
+     * Find size of pointer p.
+     * Returns 0 if not a gc'd pointer
+     */
+    size_t findSize(void *p)
+    {
+        Pool*  pool;
+        size_t size = 0;
+
+        pool = findPool(p);
+        if (pool)
+        {
+            size_t pagenum;
+            Bins   bin;
+
+            pagenum = cast(size_t)(p - pool.baseAddr) / PAGESIZE;
+            bin = cast(Bins)pool.pagetable[pagenum];
+            size = binsize[bin];
+            if (bin == B_PAGE)
+            {   size_t npages = pool.ncommitted;
+                ubyte* pt;
+                size_t i;
+
+                pt = &pool.pagetable[0];
+                for (i = pagenum + 1; i < npages; i++)
+                {
+                    if (pt[i] != B_PAGEPLUS)
+                        break;
+                }
+                size = (i - pagenum) * PAGESIZE;
+            }
+        }
+        return size;
+    }
+
+
+    /**
+     *
+     */
+    BlkInfo getInfo(void* p)
+    {
+        Pool*   pool;
+        BlkInfo info;
+
+        pool = findPool(p);
+        if (pool)
+        {
+            size_t offset = cast(size_t)(p - pool.baseAddr);
+            size_t pn = offset / PAGESIZE;
+            Bins   bin = cast(Bins)pool.pagetable[pn];
+
+            ////////////////////////////////////////////////////////////////////
+            // findAddr
+            ////////////////////////////////////////////////////////////////////
+
+            if (bin <= B_PAGE)
+            {
+                info.base = pool.baseAddr + (offset & notbinsize[bin]);
+            }
+            else if (bin == B_PAGEPLUS)
+            {
+                do
+                {   --pn, offset -= PAGESIZE;
+                } while (cast(Bins)pool.pagetable[pn] == B_PAGEPLUS);
+
+                info.base = pool.baseAddr + (offset & (offset.max ^ (PAGESIZE-1)));
+
+                // fix bin for use by size calc below
+                bin = cast(Bins)pool.pagetable[pn];
+            }
+
+            ////////////////////////////////////////////////////////////////////
+            // findSize
+            ////////////////////////////////////////////////////////////////////
+
+            info.size = binsize[bin];
+            if (bin == B_PAGE)
+            {   size_t npages = pool.ncommitted;
+                ubyte* pt;
+                size_t i;
+
+                pt = &pool.pagetable[0];
+                for (i = pn + 1; i < npages; i++)
+                {
+                    if (pt[i] != B_PAGEPLUS)
+                        break;
+                }
+                info.size = (i - pn) * PAGESIZE;
+            }
+
+            ////////////////////////////////////////////////////////////////////
+            // getBits
+            ////////////////////////////////////////////////////////////////////
+
+            info.attr = getBits(pool, cast(size_t)(offset / 16));
+        }
+        return info;
+    }
+
+
+    /**
+     * Compute bin for size.
+     */
+    static Bins findBin(size_t size)
+    {   Bins bin;
+
+        if (size <= 256)
+        {
+            if (size <= 64)
+            {
+                if (size <= 16)
+                    bin = B_16;
+                else if (size <= 32)
+                    bin = B_32;
+                else
+                    bin = B_64;
+            }
+            else
+            {
+                if (size <= 128)
+                    bin = B_128;
+                else
+                    bin = B_256;
+            }
+        }
+        else
+        {
+            if (size <= 1024)
+            {
+                if (size <= 512)
+                    bin = B_512;
+                else
+                    bin = B_1024;
+            }
+            else
+            {
+                if (size <= 2048)
+                    bin = B_2048;
+                else
+                    bin = B_PAGE;
+            }
+        }
+        return bin;
+    }
+
+
+    /**
+     * Allocate a new pool of at least size bytes.
+     * Sort it into pooltable[].
+     * Mark all memory in the pool as B_FREE.
+     * Return the actual number of bytes reserved or 0 on error.
+     */
+    size_t reserve(size_t size)
+    {
+        size_t npages = (size + PAGESIZE - 1) / PAGESIZE;
+        Pool*  pool = newPool(npages);
+
+        if (!pool || pool.extendPages(npages) == OPFAIL)
+            return 0;
+        return pool.ncommitted * PAGESIZE;
+    }
+
+
+    /**
+     * Minimizes physical memory usage by returning free pools to the OS.
+     */
+    void minimize()
+    {
+        size_t n;
+        size_t pn;
+        Pool*  pool;
+        size_t ncommitted;
+
+        for (n = 0; n < npools; n++)
+        {
+            pool = pooltable[n];
+            ncommitted = pool.ncommitted;
+            for (pn = 0; pn < ncommitted; pn++)
+            {
+                if (cast(Bins)pool.pagetable[pn] != B_FREE)
+                    break;
+            }
+            if (pn < ncommitted)
+            {
+                n++;
+                continue;
+            }
+            pool.Dtor();
+            cstdlib.free(pool);
+            memmove(pooltable + n,
+                    pooltable + n + 1,
+                    (--npools - n) * (Pool*).sizeof);
+            minAddr = pooltable[0].baseAddr;
+            maxAddr = pooltable[npools - 1].topAddr;
+        }
+    }
+
+
+    /**
+     * Allocate a chunk of memory that is larger than a page.
+     * Return null if out of memory.
+     */
+    void *bigAlloc(size_t size)
+    {
+        Pool*  pool;
+        size_t npages;
+        size_t n;
+        size_t pn;
+        size_t freedpages;
+        void*  p;
+        int    state;
+
+        npages = (size + PAGESIZE - 1) / PAGESIZE;
+
+        for (state = 0; ; )
+        {
+            // This code could use some refinement when repeatedly
+            // allocating very large arrays.
+
+            for (n = 0; n < npools; n++)
+            {
+                pool = pooltable[n];
+                pn = pool.allocPages(npages);
+                if (pn != OPFAIL)
+                    goto L1;
+            }
+
+            // Failed
+            switch (state)
+            {
+            case 0:
+                if (disabled)
+                {   state = 1;
+                    continue;
+                }
+                // Try collecting
+                freedpages = fullcollectshell();
+                if (freedpages >= npools * ((POOLSIZE / PAGESIZE) / 4))
+                {   state = 1;
+                    continue;
+                }
+                // Release empty pools to prevent bloat
+                minimize();
+                // Allocate new pool
+                pool = newPool(npages);
+                if (!pool)
+                {   state = 2;
+                    continue;
+                }
+                pn = pool.allocPages(npages);
+                assert(pn != OPFAIL);
+                goto L1;
+            case 1:
+                // Release empty pools to prevent bloat
+                minimize();
+                // Allocate new pool
+                pool = newPool(npages);
+                if (!pool)
+                    goto Lnomemory;
+                pn = pool.allocPages(npages);
+                assert(pn != OPFAIL);
+                goto L1;
+            case 2:
+                goto Lnomemory;
+            default:
+                assert(false);
+            }
+        }
+
+      L1:
+        pool.pagetable[pn] = B_PAGE;
+        if (npages > 1)
+            memset(&pool.pagetable[pn + 1], B_PAGEPLUS, npages - 1);
+        p = pool.baseAddr + pn * PAGESIZE;
+        memset(cast(char *)p + size, 0, npages * PAGESIZE - size);
+        debug (MEMSTOMP) memset(p, 0xF1, size);
+        //debug(PRINTF) printf("\tp = %x\n", p);
+        return p;
+
+      Lnomemory:
+        return null; // let mallocNoSync handle the error
+    }
+
+
+    /**
+     * Allocate a new pool with at least npages in it.
+     * Sort it into pooltable[].
+     * Return null if failed.
+     */
+    Pool *newPool(size_t npages)
+    {
+        Pool*  pool;
+        Pool** newpooltable;
+        size_t newnpools;
+        size_t i;
+
+        //debug(PRINTF) printf("************Gcx::newPool(npages = %d)****************\n", npages);
+
+        // Round up to COMMITSIZE pages
+        npages = (npages + (COMMITSIZE/PAGESIZE) - 1) & ~(COMMITSIZE/PAGESIZE - 1);
+
+        // Minimum of POOLSIZE
+        if (npages < POOLSIZE/PAGESIZE)
+            npages = POOLSIZE/PAGESIZE;
+        else if (npages > POOLSIZE/PAGESIZE)
+        {   // Give us 150% of requested size, so there's room to extend
+            auto n = npages + (npages >> 1);
+            if (n < size_t.max/PAGESIZE)
+                npages = n;
+        }
+
+        // Allocate successively larger pools up to 8 megs
+        if (npools)
+        {   size_t n;
+
+            n = npools;
+            if (n > 8)
+                n = 8;                  // cap pool size at 8 megs
+            n *= (POOLSIZE / PAGESIZE);
+            if (npages < n)
+                npages = n;
+        }
+
+        pool = cast(Pool *)cstdlib.calloc(1, Pool.sizeof);
+        if (pool)
+        {
+            pool.initialize(npages);
+            if (!pool.baseAddr)
+                goto Lerr;
+
+            newnpools = npools + 1;
+            newpooltable = cast(Pool **)cstdlib.realloc(pooltable, newnpools * (Pool *).sizeof);
+            if (!newpooltable)
+                goto Lerr;
+
+            // Sort pool into newpooltable[]
+            for (i = 0; i < npools; i++)
+            {
+                if (pool.opCmp(newpooltable[i]) < 0)
+                     break;
+            }
+            memmove(newpooltable + i + 1, newpooltable + i, (npools - i) * (Pool *).sizeof);
+            newpooltable[i] = pool;
+
+            pooltable = newpooltable;
+            npools = newnpools;
+
+            minAddr = pooltable[0].baseAddr;
+            maxAddr = pooltable[npools - 1].topAddr;
+        }
+        return pool;
+
+      Lerr:
+        pool.Dtor();
+        cstdlib.free(pool);
+        return null;
+    }
+
+
+    /**
+     * Allocate a page of bin's.
+     * Returns:
+     *  0       failed
+     */
+    int allocPage(Bins bin)
+    {
+        Pool*  pool;
+        size_t n;
+        size_t pn;
+        byte*  p;
+        byte*  ptop;
+
+        //debug(PRINTF) printf("Gcx::allocPage(bin = %d)\n", bin);
+        for (n = 0; n < npools; n++)
+        {
+            pool = pooltable[n];
+            pn = pool.allocPages(1);
+            if (pn != OPFAIL)
+                goto L1;
+        }
+        return 0;               // failed
+
+      L1:
+        pool.pagetable[pn] = cast(ubyte)bin;
+
+        // Convert page to free list
+        size_t size = binsize[bin];
+        List **b = &bucket[bin];
+
+        p = pool.baseAddr + pn * PAGESIZE;
+        ptop = p + PAGESIZE;
+        for (; p < ptop; p += size)
+        {
+            (cast(List *)p).next = *b;
+            *b = cast(List *)p;
+        }
+        return 1;
+    }
+
+
+    /**
+     * Search a range of memory values and mark any pointers into the GC pool.
+     */
+    void mark(void *pbot, void *ptop)
+    {
+        void **p1 = cast(void **)pbot;
+        void **p2 = cast(void **)ptop;
+        size_t pcache = 0;
+        uint changes = 0;
+
+        //printf("marking range: %p -> %p\n", pbot, ptop);
+        for (; p1 < p2; p1++)
+        {
+            Pool *pool;
+            byte *p = cast(byte *)(*p1);
+
+            //if (log) debug(PRINTF) printf("\tmark %x\n", p);
+            if (p >= minAddr && p < maxAddr)
+            {
+                if ((cast(size_t)p & ~(PAGESIZE-1)) == pcache)
+                    continue;
+
+                pool = findPool(p);
+                if (pool)
+                {
+                    size_t offset = cast(size_t)(p - pool.baseAddr);
+                    size_t biti;
+                    size_t pn = offset / PAGESIZE;
+                    Bins   bin = cast(Bins)pool.pagetable[pn];
+
+                    //debug(PRINTF) printf("\t\tfound pool %x, base=%x, pn = %d, bin = %d, biti = x%x\n", pool, pool.baseAddr, pn, bin, biti);
+
+                    // Adjust bit to be at start of allocated memory block
+                    if (bin <= B_PAGE)
+                    {
+                        biti = (offset & notbinsize[bin]) >> 4;
+                        //debug(PRINTF) printf("\t\tbiti = x%x\n", biti);
+                    }
+                    else if (bin == B_PAGEPLUS)
+                    {
+                        do
+                        {   --pn;
+                        } while (cast(Bins)pool.pagetable[pn] == B_PAGEPLUS);
+                        biti = pn * (PAGESIZE / 16);
+                    }
+                    else
+                    {
+                        // Don't mark bits in B_FREE or B_UNCOMMITTED pages
+                        continue;
+                    }
+
+                    if (bin >= B_PAGE) // Cache B_PAGE and B_PAGEPLUS lookups
+                        pcache = cast(size_t)p & ~(PAGESIZE-1);
+
+                    //debug(PRINTF) printf("\t\tmark(x%x) = %d\n", biti, pool.mark.test(biti));
+                    if (!pool.mark.test(biti))
+                    {
+                        //if (log) debug(PRINTF) printf("\t\tmarking %x\n", p);
+                        pool.mark.set(biti);
+                        if (!pool.noscan.test(biti))
+                        {
+                            pool.scan.set(biti);
+                            changes = 1;
+                        }
+                        log_parent(sentinel_add(pool.baseAddr + biti * 16), sentinel_add(pbot));
+                    }
+                }
+            }
+        }
+        anychanges |= changes;
+    }
+
+
+    /**
+     * Return number of full pages free'd.
+     */
+    size_t fullcollectshell()
+    {
+        // The purpose of the 'shell' is to ensure all the registers
+        // get put on the stack so they'll be scanned
+        void *sp;
+        size_t result;
+        version (GNU)
+        {
+            __builtin_unwind_init();
+            sp = & sp;
+        }
+        else
+        {
+        asm
+        {
+            pushad              ;
+            mov sp[EBP],ESP     ;
+        }
+        }
+        result = fullcollect(sp);
+        version (GNU)
+        {
+            // nothing to do
+        }
+        else
+        {
+        asm
+        {
+            popad               ;
+        }
+        }
+        return result;
+    }
+
+
+    /**
+     *
+     */
+    size_t fullcollect(void *stackTop)
+    {
+        size_t n;
+        Pool*  pool;
+
+        debug(COLLECT_PRINTF) printf("Gcx.fullcollect()\n");
+
+        thread_suspendAll();
+
+        p_cache = null;
+        size_cache = 0;
+
+        anychanges = 0;
+        for (n = 0; n < npools; n++)
+        {
+            pool = pooltable[n];
+            pool.mark.zero();
+            pool.scan.zero();
+            pool.freebits.zero();
+        }
+
+        // Mark each free entry, so it doesn't get scanned
+        for (n = 0; n < B_PAGE; n++)
+        {
+            for (List *list = bucket[n]; list; list = list.next)
+            {
+                pool = findPool(list);
+                assert(pool);
+                pool.freebits.set(cast(size_t)(cast(byte*)list - pool.baseAddr) / 16);
+            }
+        }
+
+        for (n = 0; n < npools; n++)
+        {
+            pool = pooltable[n];
+            pool.mark.copy(&pool.freebits);
+        }
+
+        rt_scanStaticData( &mark );
+
+        version (MULTI_THREADED)
+        {
+            if (!noStack)
+            {
+                // Scan stacks and registers for each paused thread
+                thread_scanAll( &mark, stackTop );
+            }
+        }
+        else
+        {
+            if (!noStack)
+            {
+                // Scan stack for main thread
+                debug(PRINTF) printf(" scan stack bot = %x, top = %x\n", stackTop, stackBottom);
+                version (STACKGROWSDOWN)
+                    mark(stackTop, stackBottom);
+                else
+                    mark(stackBottom, stackTop);
+            }
+        }
+
+        // Scan roots[]
+        debug(COLLECT_PRINTF) printf("scan roots[]\n");
+        mark(roots, roots + nroots);
+
+        // Scan ranges[]
+        debug(COLLECT_PRINTF) printf("scan ranges[]\n");
+        //log++;
+        for (n = 0; n < nranges; n++)
+        {
+            debug(COLLECT_PRINTF) printf("\t%x .. %x\n", ranges[n].pbot, ranges[n].ptop);
+            mark(ranges[n].pbot, ranges[n].ptop);
+        }
+        //log--;
+
+        debug(COLLECT_PRINTF) printf("\tscan heap\n");
+        while (anychanges)
+        {
+            anychanges = 0;
+            for (n = 0; n < npools; n++)
+            {
+                uint *bbase;
+                uint *b;
+                uint *btop;
+
+                pool = pooltable[n];
+
+                bbase = pool.scan.base();
+                btop = bbase + pool.scan.nwords;
+                for (b = bbase; b < btop;)
+                {   Bins   bin;
+                    size_t pn;
+                    size_t u;
+                    size_t bitm;
+                    byte*  o;
+
+                    bitm = *b;
+                    if (!bitm)
+                    {   b++;
+                        continue;
+                    }
+                    *b = 0;
+
+                    o = pool.baseAddr + (b - bbase) * 32 * 16;
+                    if (!(bitm & 0xFFFF))
+                    {
+                        bitm >>= 16;
+                        o += 16 * 16;
+                    }
+                    for (; bitm; o += 16, bitm >>= 1)
+                    {
+                        if (!(bitm & 1))
+                            continue;
+
+                        pn = cast(size_t)(o - pool.baseAddr) / PAGESIZE;
+                        bin = cast(Bins)pool.pagetable[pn];
+                        if (bin < B_PAGE)
+                        {
+                            mark(o, o + binsize[bin]);
+                        }
+                        else if (bin == B_PAGE || bin == B_PAGEPLUS)
+                        {
+                            if (bin == B_PAGEPLUS)
+                            {
+                                while (pool.pagetable[pn - 1] != B_PAGE)
+                                    pn--;
+                            }
+                            u = 1;
+                            while (pn + u < pool.ncommitted && pool.pagetable[pn + u] == B_PAGEPLUS)
+                                u++;
+                            mark(o, o + u * PAGESIZE);
+                        }
+                    }
+                }
+            }
+        }
+
+        thread_resumeAll();
+
+        // Free up everything not marked
+        debug(COLLECT_PRINTF) printf("\tfree'ing\n");
+        size_t freedpages = 0;
+        size_t freed = 0;
+        for (n = 0; n < npools; n++)
+        {   size_t pn;
+            size_t ncommitted;
+            uint*  bbase;
+
+            pool = pooltable[n];
+            bbase = pool.mark.base();
+            ncommitted = pool.ncommitted;
+            for (pn = 0; pn < ncommitted; pn++, bbase += PAGESIZE / (32 * 16))
+            {
+                Bins bin = cast(Bins)pool.pagetable[pn];
+
+                if (bin < B_PAGE)
+                {   byte* p;
+                    byte* ptop;
+                    size_t biti;
+                    size_t bitstride;
+                    auto   size = binsize[bin];
+
+                    p = pool.baseAddr + pn * PAGESIZE;
+                    ptop = p + PAGESIZE;
+                    biti = pn * (PAGESIZE/16);
+                    bitstride = size / 16;
+
+    version(none) // BUG: doesn't work because freebits() must also be cleared
+    {
+                    // If free'd entire page
+                    if (bbase[0] == 0 && bbase[1] == 0 && bbase[2] == 0 && bbase[3] == 0 &&
+                        bbase[4] == 0 && bbase[5] == 0 && bbase[6] == 0 && bbase[7] == 0)
+                    {
+                        for (; p < ptop; p += size, biti += bitstride)
+                        {
+                            if (pool.finals.nbits && pool.finals.testClear(biti))
+                                rt_finalize(cast(List *)sentinel_add(p), false/*noStack > 0*/);
+                            gcx.clrBits(pool, biti, BlkAttr.ALL_BITS);
+
+                            List *list = cast(List *)p;
+                            //debug(PRINTF) printf("\tcollecting %x\n", list);
+                            log_free(sentinel_add(list));
+
+                            debug (MEMSTOMP) memset(p, 0xF3, size);
+                        }
+                        pool.pagetable[pn] = B_FREE;
+                        freed += PAGESIZE;
+                        //debug(PRINTF) printf("freeing entire page %d\n", pn);
+                        continue;
+                    }
+    }
+                    for (; p < ptop; p += size, biti += bitstride)
+                    {
+                        if (!pool.mark.test(biti))
+                        {
+                            sentinel_Invariant(sentinel_add(p));
+
+                            pool.freebits.set(biti);
+                            if (pool.finals.nbits && pool.finals.testClear(biti))
+                                rt_finalize(cast(List *)sentinel_add(p), false/*noStack > 0*/);
+                            clrBits(pool, biti, BlkAttr.ALL_BITS);
+
+                            List *list = cast(List *)p;
+                            debug(PRINTF) printf("\tcollecting %x\n", list);
+                            log_free(sentinel_add(list));
+
+                            debug (MEMSTOMP) memset(p, 0xF3, size);
+
+                            freed += size;
+                        }
+                    }
+                }
+                else if (bin == B_PAGE)
+                {   size_t biti = pn * (PAGESIZE / 16);
+
+                    if (!pool.mark.test(biti))
+                    {   byte *p = pool.baseAddr + pn * PAGESIZE;
+
+                        sentinel_Invariant(sentinel_add(p));
+                        if (pool.finals.nbits && pool.finals.testClear(biti))
+                            rt_finalize(sentinel_add(p), false/*noStack > 0*/);
+                        clrBits(pool, biti, BlkAttr.ALL_BITS);
+
+                        debug(COLLECT_PRINTF) printf("\tcollecting big %x\n", p);
+                        log_free(sentinel_add(p));
+                        pool.pagetable[pn] = B_FREE;
+                        freedpages++;
+                        debug (MEMSTOMP) memset(p, 0xF3, PAGESIZE);
+                        while (pn + 1 < ncommitted && pool.pagetable[pn + 1] == B_PAGEPLUS)
+                        {
+                            pn++;
+                            pool.pagetable[pn] = B_FREE;
+                            freedpages++;
+
+                            debug (MEMSTOMP)
+                            {   p += PAGESIZE;
+                                memset(p, 0xF3, PAGESIZE);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        // Zero buckets
+        bucket[] = null;
+
+        // Free complete pages, rebuild free list
+        debug(COLLECT_PRINTF) printf("\tfree complete pages\n");
+        size_t recoveredpages = 0;
+        for (n = 0; n < npools; n++)
+        {   size_t pn;
+            size_t ncommitted;
+
+            pool = pooltable[n];
+            ncommitted = pool.ncommitted;
+            for (pn = 0; pn < ncommitted; pn++)
+            {
+                Bins   bin = cast(Bins)pool.pagetable[pn];
+                size_t biti;
+                size_t u;
+
+                if (bin < B_PAGE)
+                {
+                    size_t size = binsize[bin];
+                    size_t bitstride = size / 16;
+                    size_t bitbase = pn * (PAGESIZE / 16);
+                    size_t bittop = bitbase + (PAGESIZE / 16);
+                    byte*  p;
+
+                    biti = bitbase;
+                    for (biti = bitbase; biti < bittop; biti += bitstride)
+                    {   if (!pool.freebits.test(biti))
+                            goto Lnotfree;
+                    }
+                    pool.pagetable[pn] = B_FREE;
+                    recoveredpages++;
+                    continue;
+
+                 Lnotfree:
+                    p = pool.baseAddr + pn * PAGESIZE;
+                    for (u = 0; u < PAGESIZE; u += size)
+                    {   biti = bitbase + u / 16;
+                        if (pool.freebits.test(biti))
+                        {   List *list;
+
+                            list = cast(List *)(p + u);
+                            if (list.next != bucket[bin])       // avoid unnecessary writes
+                                list.next = bucket[bin];
+                            bucket[bin] = list;
+                        }
+                    }
+                }
+            }
+        }
+
+        debug(COLLECT_PRINTF) printf("recovered pages = %d\n", recoveredpages);
+        debug(COLLECT_PRINTF) printf("\tfree'd %u bytes, %u pages from %u pools\n", freed, freedpages, npools);
+
+        return freedpages + recoveredpages;
+    }
+
+
+    /**
+     *
+     */
+    uint getBits(Pool* pool, size_t biti)
+    in
+    {
+        assert( pool );
+    }
+    body
+    {
+        uint bits;
+
+        if (pool.finals.nbits &&
+            pool.finals.test(biti))
+            bits |= BlkAttr.FINALIZE;
+        if (pool.noscan.test(biti))
+            bits |= BlkAttr.NO_SCAN;
+//        if (pool.nomove.nbits &&
+//            pool.nomove.test(biti))
+//            bits |= BlkAttr.NO_MOVE;
+        return bits;
+    }
+
+
+    /**
+     *
+     */
+    void setBits(Pool* pool, size_t biti, uint mask)
+    in
+    {
+        assert( pool );
+    }
+    body
+    {
+        if (mask & BlkAttr.FINALIZE)
+        {
+            if (!pool.finals.nbits)
+                pool.finals.alloc(pool.mark.nbits);
+            pool.finals.set(biti);
+        }
+        if (mask & BlkAttr.NO_SCAN)
+        {
+            pool.noscan.set(biti);
+        }
+//        if (mask & BlkAttr.NO_MOVE)
+//        {
+//            if (!pool.nomove.nbits)
+//                pool.nomove.alloc(pool.mark.nbits);
+//            pool.nomove.set(biti);
+//        }
+    }
+
+
+    /**
+     *
+     */
+    void clrBits(Pool* pool, size_t biti, uint mask)
+    in
+    {
+        assert( pool );
+    }
+    body
+    {
+        if (mask & BlkAttr.FINALIZE && pool.finals.nbits)
+            pool.finals.clear(biti);
+        if (mask & BlkAttr.NO_SCAN)
+            pool.noscan.clear(biti);
+//        if (mask & BlkAttr.NO_MOVE && pool.nomove.nbits)
+//            pool.nomove.clear(biti);
+    }
+
+
+    /***** Leak Detector ******/
+
+
+    debug (LOGGING)
+    {
+        LogArray current;
+        LogArray prev;
+
+
+        void log_init()
+        {
+            //debug(PRINTF) printf("+log_init()\n");
+            current.reserve(1000);
+            prev.reserve(1000);
+            //debug(PRINTF) printf("-log_init()\n");
+        }
+
+
+        void log_malloc(void *p, size_t size)
+        {
+            //debug(PRINTF) printf("+log_malloc(p = %x, size = %d)\n", p, size);
+            Log log;
+
+            log.p = p;
+            log.size = size;
+            log.line = GC.line;
+            log.file = GC.file;
+            log.parent = null;
+
+            GC.line = 0;
+            GC.file = null;
+
+            current.push(log);
+            //debug(PRINTF) printf("-log_malloc()\n");
+        }
+
+
+        void log_free(void *p)
+        {
+            //debug(PRINTF) printf("+log_free(%x)\n", p);
+            size_t i;
+
+            i = current.find(p);
+            if (i == OPFAIL)
+            {
+                debug(PRINTF) printf("free'ing unallocated memory %x\n", p);
+            }
+            else
+                current.remove(i);
+            //debug(PRINTF) printf("-log_free()\n");
+        }
+
+
+        void log_collect()
+        {
+            //debug(PRINTF) printf("+log_collect()\n");
+            // Print everything in current that is not in prev
+
+            debug(PRINTF) printf("New pointers this cycle: --------------------------------\n");
+            size_t used = 0;
+            for (size_t i = 0; i < current.dim; i++)
+            {
+                size_t j;
+
+                j = prev.find(current.data[i].p);
+                if (j == OPFAIL)
+                    current.data[i].print();
+                else
+                    used++;
+            }
+
+            debug(PRINTF) printf("All roots this cycle: --------------------------------\n");
+            for (size_t i = 0; i < current.dim; i++)
+            {
+                void *p;
+                size_t j;
+
+                p = current.data[i].p;
+                if (!findPool(current.data[i].parent))
+                {
+                    j = prev.find(current.data[i].p);
+                    if (j == OPFAIL)
+                        debug(PRINTF) printf("N");
+                    else
+                        debug(PRINTF) printf(" ");;
+                    current.data[i].print();
+                }
+            }
+
+            debug(PRINTF) printf("Used = %d-------------------------------------------------\n", used);
+            prev.copy(&current);
+
+            debug(PRINTF) printf("-log_collect()\n");
+        }
+
+
+        void log_parent(void *p, void *parent)
+        {
+            //debug(PRINTF) printf("+log_parent()\n");
+            size_t i;
+
+            i = current.find(p);
+            if (i == OPFAIL)
+            {
+                debug(PRINTF) printf("parent'ing unallocated memory %x, parent = %x\n", p, parent);
+                Pool *pool;
+                pool = findPool(p);
+                assert(pool);
+                size_t offset = cast(size_t)(p - pool.baseAddr);
+                size_t biti;
+                size_t pn = offset / PAGESIZE;
+                Bins bin = cast(Bins)pool.pagetable[pn];
+                biti = (offset & notbinsize[bin]);
+                debug(PRINTF) printf("\tbin = %d, offset = x%x, biti = x%x\n", bin, offset, biti);
+            }
+            else
+            {
+                current.data[i].parent = parent;
+            }
+            //debug(PRINTF) printf("-log_parent()\n");
+        }
+
+    }
+    else
+    {
+        void log_init() { }
+        void log_malloc(void *p, size_t size) { }
+        void log_free(void *p) { }
+        void log_collect() { }
+        void log_parent(void *p, void *parent) { }
+    }
+}
+
+
+/* ============================ Pool  =============================== */
+
+
+struct Pool
+{
+    byte* baseAddr;
+    byte* topAddr;
+    GCBits mark;        // entries already scanned, or should not be scanned
+    GCBits scan;        // entries that need to be scanned
+    GCBits freebits;    // entries that are on the free list
+    GCBits finals;      // entries that need finalizer run on them
+    GCBits noscan;      // entries that should not be scanned
+
+    size_t npages;
+    size_t ncommitted;    // ncommitted <= npages
+    ubyte* pagetable;
+
+
+    void initialize(size_t npages)
+    {
+        size_t poolsize;
+
+        //debug(PRINTF) printf("Pool::Pool(%u)\n", npages);
+        poolsize = npages * PAGESIZE;
+        assert(poolsize >= POOLSIZE);
+        baseAddr = cast(byte *)os_mem_map(poolsize);
+
+        // Some of the code depends on page alignment of memory pools
+        assert((cast(size_t)baseAddr & (PAGESIZE - 1)) == 0);
+
+        if (!baseAddr)
+        {
+            //debug(PRINTF) printf("GC fail: poolsize = x%x, errno = %d\n", poolsize, errno);
+            //debug(PRINTF) printf("message = '%s'\n", sys_errlist[errno]);
+
+            npages = 0;
+            poolsize = 0;
+        }
+        //assert(baseAddr);
+        topAddr = baseAddr + poolsize;
+
+        mark.alloc(cast(size_t)poolsize / 16);
+        scan.alloc(cast(size_t)poolsize / 16);
+        freebits.alloc(cast(size_t)poolsize / 16);
+        noscan.alloc(cast(size_t)poolsize / 16);
+
+        pagetable = cast(ubyte*)cstdlib.malloc(npages);
+        if (!pagetable)
+            onOutOfMemoryError();
+        memset(pagetable, B_UNCOMMITTED, npages);
+
+        this.npages = npages;
+        ncommitted = 0;
+    }
+
+
+    void Dtor()
+    {
+        if (baseAddr)
+        {
+            int result;
+
+            if (ncommitted)
+            {
+                result = os_mem_decommit(baseAddr, 0, ncommitted * PAGESIZE);
+                assert(result == 0);
+                ncommitted = 0;
+            }
+
+            if (npages)
+            {
+                result = os_mem_unmap(baseAddr, npages * PAGESIZE);
+                assert(result == 0);
+                npages = 0;
+            }
+
+            baseAddr = null;
+            topAddr = null;
+        }
+        if (pagetable)
+            cstdlib.free(pagetable);
+
+        mark.Dtor();
+        scan.Dtor();
+        freebits.Dtor();
+        finals.Dtor();
+        noscan.Dtor();
+    }
+
+
+    void Invariant() { }
+
+
+    invariant()
+    {
+        //mark.Invariant();
+        //scan.Invariant();
+        //freebits.Invariant();
+        //finals.Invariant();
+        //noscan.Invariant();
+
+        if (baseAddr)
+        {
+            //if (baseAddr + npages * PAGESIZE != topAddr)
+                //printf("baseAddr = %p, npages = %d, topAddr = %p\n", baseAddr, npages, topAddr);
+            assert(baseAddr + npages * PAGESIZE == topAddr);
+            assert(ncommitted <= npages);
+        }
+
+        for (size_t i = 0; i < npages; i++)
+        {   Bins bin = cast(Bins)pagetable[i];
+
+            assert(bin < B_MAX);
+        }
+    }
+
+
+    /**
+     * Allocate n pages from Pool.
+     * Returns OPFAIL on failure.
+     */
+    size_t allocPages(size_t n)
+    {
+        size_t i;
+        size_t n2;
+
+        //debug(PRINTF) printf("Pool::allocPages(n = %d)\n", n);
+        n2 = n;
+        for (i = 0; i < ncommitted; i++)
+        {
+            if (pagetable[i] == B_FREE)
+            {
+                if (--n2 == 0)
+                {   //debug(PRINTF) printf("\texisting pn = %d\n", i - n + 1);
+                    return i - n + 1;
+                }
+            }
+            else
+                n2 = n;
+        }
+        return extendPages(n);
+    }
+
+    /**
+     * Extend Pool by n pages.
+     * Returns OPFAIL on failure.
+     */
+    size_t extendPages(size_t n)
+    {
+        //debug(PRINTF) printf("Pool::extendPages(n = %d)\n", n);
+        if (ncommitted + n <= npages)
+        {
+            size_t tocommit;
+
+            tocommit = (n + (COMMITSIZE/PAGESIZE) - 1) & ~(COMMITSIZE/PAGESIZE - 1);
+            if (ncommitted + tocommit > npages)
+                tocommit = npages - ncommitted;
+            //debug(PRINTF) printf("\tlooking to commit %d more pages\n", tocommit);
+            //fflush(stdout);
+            if (os_mem_commit(baseAddr, ncommitted * PAGESIZE, tocommit * PAGESIZE) == 0)
+            {
+                memset(pagetable + ncommitted, B_FREE, tocommit);
+                auto i = ncommitted;
+                ncommitted += tocommit;
+
+                while (i && pagetable[i - 1] == B_FREE)
+                    i--;
+
+                return i;
+            }
+            //debug(PRINTF) printf("\tfailed to commit %d pages\n", tocommit);
+        }
+
+        return OPFAIL;
+    }
+
+
+    /**
+     * Free npages pages starting with pagenum.
+     */
+    void freePages(size_t pagenum, size_t npages)
+    {
+        memset(&pagetable[pagenum], B_FREE, npages);
+    }
+
+
+    /**
+     * Used for sorting pooltable[]
+     */
+    int opCmp(Pool *p2)
+    {
+        if (baseAddr < p2.baseAddr)
+            return -1;
+        else
+        return cast(int)(baseAddr > p2.baseAddr);
+    }
+}
+
+
+/* ============================ SENTINEL =============================== */
+
+
+version (SENTINEL)
+{
+    const size_t SENTINEL_PRE = cast(size_t) 0xF4F4F4F4F4F4F4F4UL; // 32 or 64 bits
+    const ubyte SENTINEL_POST = 0xF5;           // 8 bits
+    const uint SENTINEL_EXTRA = 2 * size_t.sizeof + 1;
+
+
+    size_t* sentinel_size(void *p)  { return &(cast(size_t *)p)[-2]; }
+    size_t* sentinel_pre(void *p)   { return &(cast(size_t *)p)[-1]; }
+    ubyte* sentinel_post(void *p) { return &(cast(ubyte *)p)[*sentinel_size(p)]; }
+
+
+    void sentinel_init(void *p, size_t size)
+    {
+        *sentinel_size(p) = size;
+        *sentinel_pre(p) = SENTINEL_PRE;
+        *sentinel_post(p) = SENTINEL_POST;
+    }
+
+
+    void sentinel_Invariant(void *p)
+    {
+        assert(*sentinel_pre(p) == SENTINEL_PRE);
+        assert(*sentinel_post(p) == SENTINEL_POST);
+    }
+
+
+    void *sentinel_add(void *p)
+    {
+        return p + 2 * size_t.sizeof;
+    }
+
+
+    void *sentinel_sub(void *p)
+    {
+        return p - 2 * size_t.sizeof;
+    }
+}
+else
+{
+    const uint SENTINEL_EXTRA = 0;
+
+
+    void sentinel_init(void *p, size_t size)
+    {
+    }
+
+
+    void sentinel_Invariant(void *p)
+    {
+    }
+
+
+    void *sentinel_add(void *p)
+    {
+        return p;
+    }
+
+
+    void *sentinel_sub(void *p)
+    {
+        return p;
+    }
+}