object.cpp

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
// OBJECT.CPP
//
// Definitions of a Com+ Object
//



#include "common.h"

#include "vars.hpp"
#include "class.h"
#include "object.h"
#include "threads.h"
#include "excep.h"
#include "eeconfig.h"
#include "gc.h"
#ifdef FEATURE_REMOTING
#include "remoting.h"
#endif
#include "field.h"
#include "gcscan.h"
#include "argdestination.h"

#ifdef FEATURE_COMPRESSEDSTACK
void* CompressedStackObject::GetUnmanagedCompressedStack()
{
    LIMITED_METHOD_CONTRACT;  
    return ((m_compressedStackHandle != NULL)?m_compressedStackHandle->GetHandle():NULL);
}
#endif // FEATURE_COMPRESSEDSTACK

#ifndef FEATURE_PAL 
LPVOID FrameSecurityDescriptorBaseObject::GetCallerToken()
{
    LIMITED_METHOD_CONTRACT;  
    return ((m_callerToken!= NULL)?m_callerToken->GetHandle():NULL);

}

LPVOID FrameSecurityDescriptorBaseObject::GetImpersonationToken()
{
    LIMITED_METHOD_CONTRACT;  
    return ((m_impToken != NULL)?m_impToken->GetHandle():NULL);
}
#endif

SVAL_IMPL(INT32, ArrayBase, s_arrayBoundsZero);

// follow the necessary rules to get a new valid hashcode for an object
DWORD Object::ComputeHashCode()
{
    DWORD hashCode;
   
    // note that this algorithm now uses at most HASHCODE_BITS so that it will
    // fit into the objheader if the hashcode has to be moved back into the objheader
    // such as for an object that is being frozen
    do
    {
        // we use the high order bits in this case because they're more random
        hashCode = GetThread()->GetNewHashCode() >> (32-HASHCODE_BITS);
    }
    while (hashCode == 0);   // need to enforce hashCode != 0

    // verify that it really fits into HASHCODE_BITS
     _ASSERTE((hashCode & ((1<<HASHCODE_BITS)-1)) == hashCode);

    return hashCode;
}

#ifndef DACCESS_COMPILE    
INT32 Object::GetHashCodeEx()
{
    CONTRACTL
    {
        MODE_COOPERATIVE;
        THROWS;
        GC_NOTRIGGER;
        SO_TOLERANT;
    }
    CONTRACTL_END

    // This loop exists because we're inspecting the header dword of the object
    // and it may change under us because of races with other threads.
    // On top of that, it may have the spin lock bit set, in which case we're
    // not supposed to change it.
    // In all of these case, we need to retry the operation.
    DWORD iter = 0;
    DWORD dwSwitchCount = 0;
    while (true)
    {
        DWORD bits = GetHeader()->GetBits();

        if (bits & BIT_SBLK_IS_HASH_OR_SYNCBLKINDEX)
        {
            if (bits & BIT_SBLK_IS_HASHCODE)
            {
                // Common case: the object already has a hash code
                return  bits & MASK_HASHCODE;
            }
            else
            {
                // We have a sync block index. This means if we already have a hash code,
                // it is in the sync block, otherwise we generate a new one and store it there
                SyncBlock *psb = GetSyncBlock();
                DWORD hashCode = psb->GetHashCode();
                if (hashCode != 0)
                    return  hashCode;

                hashCode = ComputeHashCode();

                return psb->SetHashCode(hashCode);
            }
        }
        else
        {
            // If a thread is holding the thin lock or an appdomain index is set, we need a syncblock
            if ((bits & (SBLK_MASK_LOCK_THREADID | (SBLK_MASK_APPDOMAININDEX << SBLK_APPDOMAIN_SHIFT))) != 0)
            {
                GetSyncBlock();
                // No need to replicate the above code dealing with sync blocks
                // here - in the next iteration of the loop, we'll realize
                // we have a syncblock, and we'll do the right thing.
            }
            else
            {
                // We want to change the header in this case, so we have to check the BIT_SBLK_SPIN_LOCK bit first
                if (bits & BIT_SBLK_SPIN_LOCK)
                {
                    iter++;
                    if ((iter % 1024) != 0 && g_SystemInfo.dwNumberOfProcessors > 1)
                    {
                        YieldProcessor();           // indicate to the processor that we are spining
                    }
                    else
                    {
                        __SwitchToThread(0, ++dwSwitchCount);
                    }
                    continue;
                }

                DWORD hashCode = ComputeHashCode();

                DWORD newBits = bits | BIT_SBLK_IS_HASH_OR_SYNCBLKINDEX | BIT_SBLK_IS_HASHCODE | hashCode;

                if (GetHeader()->SetBits(newBits, bits) == bits)
                    return hashCode;
                // Header changed under us - let's restart this whole thing.
            }
        }
    }    
}
#endif // #ifndef DACCESS_COMPILE

BOOL Object::ValidateObjectWithPossibleAV()
{
    CANNOT_HAVE_CONTRACT;
    SUPPORTS_DAC;

    return GetGCSafeMethodTable()->ValidateWithPossibleAV();
}


#ifndef DACCESS_COMPILE

MethodTable *Object::GetTrueMethodTable()
{
    CONTRACT(MethodTable*)
    {
        MODE_COOPERATIVE;
        GC_NOTRIGGER;
        NOTHROW;
        SO_TOLERANT;
        POSTCONDITION(CheckPointer(RETVAL));
    }
    CONTRACT_END;

    MethodTable *mt = GetMethodTable();

#ifdef FEATURE_REMOTING    
    if(mt->IsTransparentProxy())
    {
        mt = ((TransparentProxyObject *)this)->GetMethodTableBeingProxied();
    }
    _ASSERTE(!mt->IsTransparentProxy());
#endif

    RETURN mt;
}

TypeHandle Object::GetTrueTypeHandle()
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        SO_TOLERANT;
        MODE_COOPERATIVE;
    }
    CONTRACTL_END;

    if (m_pMethTab->IsArray())
        return ((ArrayBase*) this)->GetTypeHandle();
    else
        return TypeHandle(GetTrueMethodTable());
}

// There are cases where it is not possible to get a type handle during a GC.
// If we can get the type handle, this method will return it.
// Otherwise, the method will return NULL.
TypeHandle Object::GetGCSafeTypeHandleIfPossible() const
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        if(!IsGCThread()) { MODE_COOPERATIVE; }
    } 
    CONTRACTL_END;

    // Although getting the type handle is unsafe and could cause recursive type lookups
    // in some cases, it's always safe and straightforward to get to the MethodTable.
    MethodTable * pMT = GetGCSafeMethodTable();
    _ASSERTE(pMT != NULL);

    // Don't look at types that belong to an unloading AppDomain, or else
    // pObj->GetGCSafeTypeHandle() can AV. For example, we encountered this AV when pObj
    // was an array like this:
    //     
    //     MyValueType1<MyValueType2>[] myArray
    //
    // where MyValueType1<T> & MyValueType2 are defined in different assemblies. In such
    // a case, looking up the type handle for myArray requires looking in
    // MyValueType1<T>'s module's m_AssemblyRefByNameTable, which is garbage if its
    // AppDomain is unloading.
    // 
    // Another AV was encountered in a similar case,
    // 
    //     MyRefType1<MyRefType2>[] myArray
    // 
    // where MyRefType2's module was unloaded by the time the GC occurred. In at least
    // one case, the GC was caused by the AD unload itself (AppDomain::Unload ->
    // AppDomain::Exit -> GCInterface::AddMemoryPressure -> WKS::GCHeap::GarbageCollect).
    // 
    // To protect against all scenarios, verify that
    // 
    //     * The MT of the object is not getting unloaded, OR
    //     * In the case of arrays (potentially of arrays of arrays of arrays ...), the
    //         MT of the innermost element is not getting unloaded. This then ensures the
    //         MT of the original object (i.e., array) itself must not be getting
    //         unloaded either, since the MTs of arrays and of their elements are
    //         allocated on the same loader heap, except the case where the array is
    //         Object[], in which case its MT is in mscorlib and thus doesn't unload.

    MethodTable * pMTToCheck = pMT;
    if (pMTToCheck->IsArray())
    {
        TypeHandle thElem = static_cast<const ArrayBase * const>(this)->GetArrayElementTypeHandle();

        // Ideally, we would just call thElem.GetLoaderModule() here. Unfortunately, the
        // current TypeDesc::GetLoaderModule() implementation depends on data structures
        // that might have been unloaded already. So we just simulate
        // TypeDesc::GetLoaderModule() for the limited array case that we care about. In
        // case we're dealing with an array of arrays of arrays etc. traverse until we
        // find the deepest element, and that's the type we'll check
        while (thElem.HasTypeParam()) 
        {
            thElem = thElem.GetTypeParam();
        }

        pMTToCheck = thElem.GetMethodTable();
    }

    Module * pLoaderModule = pMTToCheck->GetLoaderModule();

    BaseDomain * pBaseDomain = pLoaderModule->GetDomain();
    if ((pBaseDomain != NULL) && 
        (pBaseDomain->IsAppDomain()) && 
        (pBaseDomain->AsAppDomain()->IsUnloading()))
    {
        return NULL;
    }

    // Don't look up types that are unloading due to Collectible Assemblies. Haven't been
    // able to find a case where we actually encounter objects like this that can cause
    // problems; however, it seems prudent to add this protection just in case.
    LoaderAllocator * pLoaderAllocator = pLoaderModule->GetLoaderAllocator();
    _ASSERTE(pLoaderAllocator != NULL);
    if ((pLoaderAllocator->IsCollectible()) &&
        (ObjectHandleIsNull(pLoaderAllocator->GetLoaderAllocatorObjectHandle())))
    {
        return NULL;
    }

    // Ok, it should now be safe to get the type handle
    return GetGCSafeTypeHandle();
}

/* static */ BOOL Object::SupportsInterface(OBJECTREF pObj, MethodTable* pInterfaceMT)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        INJECT_FAULT(COMPlusThrowOM());
        PRECONDITION(CheckPointer(pInterfaceMT));
        PRECONDITION(pObj->GetTrueMethodTable()->IsRestored_NoLogging());
        PRECONDITION(pInterfaceMT->IsInterface());
    }
    CONTRACTL_END

    BOOL bSupportsItf = FALSE;

    GCPROTECT_BEGIN(pObj)
    {
        // Make sure the interface method table has been restored.
        pInterfaceMT->CheckRestore();

        // Check to see if the static class definition indicates we implement the interface.
        MethodTable * pMT = pObj->GetTrueMethodTable();
        if (pMT->CanCastToInterface(pInterfaceMT))
        {
            bSupportsItf = TRUE;
        }
#ifdef FEATURE_COMINTEROP
        else
        if (pMT->IsComObjectType())
        {
            // If this is a COM object, the static class definition might not be complete so we need
            // to check if the COM object implements the interface.
            bSupportsItf = ComObject::SupportsInterface(pObj, pInterfaceMT);
        }
#endif // FEATURE_COMINTEROP
    }
    GCPROTECT_END();

    return bSupportsItf;
}

Assembly *AssemblyBaseObject::GetAssembly()
{
    WRAPPER_NO_CONTRACT;
    return m_pAssembly->GetAssembly();
}

#ifdef _DEBUG
// Object::DEBUG_SetAppDomain specified DEBUG_ONLY in the contract to disable SO-tolerance
// checking for paths that are DEBUG-only.
//
// NOTE: currently this is only used by WIN64 allocation helpers, but they really should
//       be calling the JIT helper SetObjectAppDomain (which currently only exists for
//       x86).
void Object::DEBUG_SetAppDomain(AppDomain *pDomain)
{
    CONTRACTL
    {
        THROWS;
        GC_NOTRIGGER;
        DEBUG_ONLY;
        INJECT_FAULT(COMPlusThrowOM(););
        PRECONDITION(CheckPointer(pDomain));
    }
    CONTRACTL_END;

    /*_ASSERTE(GetThread()->IsSOTolerant());*/
    SetAppDomain(pDomain);
}
#endif

void Object::SetAppDomain(AppDomain *pDomain)
{
    CONTRACTL
    {
        THROWS;
        GC_NOTRIGGER;
        SO_INTOLERANT;
        INJECT_FAULT(COMPlusThrowOM(););
        PRECONDITION(CheckPointer(pDomain));
    }
    CONTRACTL_END;

#ifndef _DEBUG
    if (!GetMethodTable()->IsDomainNeutral())
    {
        //
        // If we have a per-app-domain method table, we can 
        // infer the app domain from the method table, so 
        // there is no reason to mark the object.
        //
        // But we don't do this in a debug build, because
        // we want to be able to detect the case when the
        // domain was unloaded from underneath an object (and
        // the MethodTable will be toast in that case.)
        //

        _ASSERTE(pDomain == GetMethodTable()->GetDomain());
    }
    else
#endif
    {
        ADIndex index = pDomain->GetIndex();
        GetHeader()->SetAppDomainIndex(index);
    }

    _ASSERTE(GetHeader()->GetAppDomainIndex().m_dwIndex != 0);
}


AppDomain *Object::GetAppDomain()
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        SO_TOLERANT;
        MODE_COOPERATIVE;
    }
    CONTRACTL_END;
#ifndef _DEBUG
    if (!GetMethodTable()->IsDomainNeutral())
        return (AppDomain*) GetMethodTable()->GetDomain();
#endif

    ADIndex index = GetHeader()->GetAppDomainIndex();

    if (index.m_dwIndex == 0)
        return NULL;

    AppDomain *pDomain = SystemDomain::TestGetAppDomainAtIndex(index);

#if CHECK_APP_DOMAIN_LEAKS
    if (! g_pConfig->AppDomainLeaks())
        return pDomain;

    if (IsAppDomainAgile())
        return NULL;

    //
    // If an object has an index of an unloaded domain (its ok to be of a 
    // domain where an unload is in progress through), go ahead
    // and make it agile. If this fails, we have an invalid reference
    // to an unloaded domain.  If it succeeds, the object is no longer
    // contained in that app domain so we can continue.
    //

    if (pDomain == NULL)
    {
        if (SystemDomain::IndexOfAppDomainBeingUnloaded() == index) {
            // if appdomain is unloading but still alive and is valid to have instances
            // in that domain, then use it.
            AppDomain *tmpDomain = SystemDomain::AppDomainBeingUnloaded();
            if (tmpDomain && tmpDomain->ShouldHaveInstances())
                pDomain = tmpDomain;
        }
        if (!pDomain && ! TrySetAppDomainAgile(FALSE))
        {
            _ASSERTE(!"Attempt to reference an object belonging to an unloaded domain");
        }
    }
#endif

    return pDomain;
}

STRINGREF AllocateString(SString sstr)
{
    CONTRACTL {
        THROWS;
        GC_TRIGGERS;
    } CONTRACTL_END;
    
    COUNT_T length = sstr.GetCount(); // count of WCHARs excluding terminating NULL
    STRINGREF strObj = AllocateString(length);
    memcpyNoGCRefs(strObj->GetBuffer(), sstr.GetUnicode(), length*sizeof(WCHAR));

    return strObj;
}

CHARARRAYREF AllocateCharArray(DWORD dwArrayLength)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
    }
    CONTRACTL_END;
    return (CHARARRAYREF)AllocatePrimitiveArray(ELEMENT_TYPE_CHAR, dwArrayLength);
}

#if CHECK_APP_DOMAIN_LEAKS

BOOL Object::IsAppDomainAgile()
{
    WRAPPER_NO_CONTRACT;
    DEBUG_ONLY_FUNCTION;

    SyncBlock *psb = PassiveGetSyncBlock();

    if (psb)
    {
        if (psb->IsAppDomainAgile())
            return TRUE;
        if (psb->IsCheckedForAppDomainAgile())
            return FALSE;
    }
    return CheckAppDomain(NULL);
}

BOOL Object::TrySetAppDomainAgile(BOOL raiseAssert)
{
    LIMITED_METHOD_CONTRACT;
    FAULT_NOT_FATAL();
    DEBUG_ONLY_FUNCTION;

    BOOL ret = TRUE;

    EX_TRY
    {
        ret = SetAppDomainAgile(raiseAssert);
    }
    EX_CATCH{}
    EX_END_CATCH(SwallowAllExceptions);

    return ret;
}


BOOL Object::ShouldCheckAppDomainAgile (BOOL raiseAssert, BOOL *pfResult)
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;
    DEBUG_ONLY_FUNCTION;

    if (!g_pConfig->AppDomainLeaks())
    {
        *pfResult = TRUE;
        return FALSE;
    }

    if (this == NULL)
    {
        *pfResult = TRUE;
        return FALSE;
    }

    if (IsAppDomainAgile())
    {
        *pfResult = TRUE;
        return FALSE;
    }

    // if it's not agile and we've already checked it, just bail early
    if (IsCheckedForAppDomainAgile())
    {
        *pfResult = FALSE;
        return FALSE;
    }

    if (IsTypeNeverAppDomainAgile())
    {
        if (raiseAssert)
            _ASSERTE(!"Attempt to reference a domain bound object from an agile location");
        *pfResult = FALSE;
        return FALSE;
    }

    //
    // Do not allow any object to be set to be agile unless we 
    // are compiling field access checking into the class.  This
    // will help guard against unintentional "agile" propagation
    // as well.
    //

    if (!IsTypeAppDomainAgile() && !IsTypeCheckAppDomainAgile()) 
    {
        if (raiseAssert)
            _ASSERTE(!"Attempt to reference a domain bound object from an agile location");
        *pfResult = FALSE;
        return FALSE;
    }

    return TRUE;
}


BOOL Object::SetAppDomainAgile(BOOL raiseAssert, SetAppDomainAgilePendingTable *pTable)
{
    CONTRACTL
    {
        THROWS;
        GC_NOTRIGGER;
        INJECT_FAULT(COMPlusThrowOM(););
        DEBUG_ONLY;
    }
    CONTRACTL_END;
    BEGIN_DEBUG_ONLY_CODE;
    BOOL fResult;
    if (!this->ShouldCheckAppDomainAgile(raiseAssert, &fResult))
        return fResult;

    //
    // If a SetAppDomainAgilePendingTable is provided, then SetAppDomainAgile
    // was called via SetAppDomainAgile.  Simply store this object in the
    // table, and let the calling SetAppDomainAgile process it later in a
    // non-recursive manner.
    //

    if (pTable == NULL)
    {
        pTable = (SetAppDomainAgilePendingTable *)ClrFlsGetValue(TlsIdx_AppDomainAgilePendingTable);
    }
    if (pTable)
    {
        //
        // If the object is already being checked (on this thread or another),
        // don't duplicate the effort.  Return TRUE to tell the caller to
        // continue processing other references.  Since we're just testing
        // the bit we don't need to take the spin lock.
        //
        
        ObjHeader* pOh = this->GetHeader();
        _ASSERTE(pOh);

        if (pOh->GetBits() & BIT_SBLK_AGILE_IN_PROGRESS)
        {
            return TRUE;
    }

        pTable->PushReference(this);
    }
    else
    {
        //
        // Initialize the table of pending objects
        //
        
        SetAppDomainAgilePendingTable table;
        class ResetPendingTable
        {
        public:
            ResetPendingTable(SetAppDomainAgilePendingTable *pTable)
            {
                ClrFlsSetValue(TlsIdx_AppDomainAgilePendingTable, pTable);
            }
            ~ResetPendingTable()
            {
                ClrFlsSetValue(TlsIdx_AppDomainAgilePendingTable, NULL);
            }
        };

        ResetPendingTable resetPendingTable(&table);

        //
        // Iterate over the table, processing all referenced objects until the
        // entire graph has its sync block marked, or a non-agile object is
        // found.  The loop will start with the current object, as though we
        // just removed it from the table as a pending reference.
        //

        Object *pObject = this;

        do
        {
            //
            // Mark the object to identify recursion.
            // ~SetAppDomainAgilePendingTable will clean up
            // BIT_SBLK_AGILE_IN_PROGRESS, so attempt to push the object first
            // in case it needs to throw an exception.
            //

            table.PushParent(pObject);

            ObjHeader* pOh = pObject->GetHeader();
            _ASSERTE(pOh);

            bool fInProgress = false;

            {
                ENTER_SPIN_LOCK(pOh);
                {
                    if (pOh->GetBits() & BIT_SBLK_AGILE_IN_PROGRESS)
                    {
                        fInProgress = true;
                    }
                    else
                    {
                        pOh->SetBit(BIT_SBLK_AGILE_IN_PROGRESS);
                    }
                }
               LEAVE_SPIN_LOCK(pOh);
            }

            if (fInProgress)
            {
                //
                // Object is already being processed, so just remove it from
                // the table and look for another object.
                //

                bool fReturnedToParent = false;
                Object *pLastObject = table.GetPendingObject(&fReturnedToParent);
                CONSISTENCY_CHECK(pLastObject == pObject && fReturnedToParent);
            }
            else
            {
                
                //
                // Finish processing this object.  Any references will be added to
                // the table.
        //

                if (!pObject->SetAppDomainAgileWorker(raiseAssert, &table))
            return FALSE;
            }

        //
            // Find the next object to explore.
        //

            for (;;)
        {
                bool fReturnedToParent;
                pObject = table.GetPendingObject(&fReturnedToParent);

                //
                // No more objects in the table?
                //

                if (!pObject)
                    break;

                //
                // If we've processed all objects reachable through an object,
                // then clear BIT_SBLK_AGILE_IN_PROGRESS, and look for another
                // object in the table.
                //

                if (fReturnedToParent)
            {
                    pOh = pObject->GetHeader();
                    _ASSERTE(pOh);

                    ENTER_SPIN_LOCK(pOh);
                    pOh->ClrBit(BIT_SBLK_AGILE_IN_PROGRESS);
                    LEAVE_SPIN_LOCK(pOh);
            }
            else
            {
                    //
                    // Re-check whether we should explore through this reference.
                    //

                    if (pObject->ShouldCheckAppDomainAgile(raiseAssert, &fResult))
                        break;
                    
                    if (!fResult)
                    return FALSE;
            }
        }
    }
        while (pObject);
    }
    END_DEBUG_ONLY_CODE;
    return TRUE;
}


BOOL Object::SetAppDomainAgileWorker(BOOL raiseAssert, SetAppDomainAgilePendingTable *pTable)
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;
    DEBUG_ONLY_FUNCTION;

    BOOL ret = TRUE;

        if (! IsTypeAppDomainAgile() && ! SetFieldsAgile(raiseAssert, pTable))
        {
            SetIsCheckedForAppDomainAgile();

            ret = FALSE;
        }
    
    if (ret)
    {
        SetSyncBlockAppDomainAgile();
    }

    return ret;
}


SetAppDomainAgilePendingTable::SetAppDomainAgilePendingTable ()
    : m_Stack(sizeof(PendingEntry))
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;
    DEBUG_ONLY_FUNCTION;
}


SetAppDomainAgilePendingTable::~SetAppDomainAgilePendingTable ()
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;
    DEBUG_ONLY_FUNCTION;

    while (TRUE)
    {
        Object *pObj;
        bool fObjMarked;
        pObj = GetPendingObject(&fObjMarked);
        if (pObj == NULL)
        {
            break;
        }
    
        if (fObjMarked)
        {
            ObjHeader* pOh = pObj->GetHeader();
            _ASSERTE(pOh);

            ENTER_SPIN_LOCK(pOh);
            pOh->ClrBit(BIT_SBLK_AGILE_IN_PROGRESS);
            LEAVE_SPIN_LOCK(pOh);
        }
}
}


void Object::SetSyncBlockAppDomainAgile()
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;
    DEBUG_ONLY_FUNCTION;

    SyncBlock *psb = PassiveGetSyncBlock();
    if (! psb)
    {
        psb = GetSyncBlock();
    }
    psb->SetIsAppDomainAgile();
}

#if CHECK_APP_DOMAIN_LEAKS
BOOL Object::CheckAppDomain(AppDomain *pAppDomain)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    DEBUG_ONLY_FUNCTION;

    if (!g_pConfig->AppDomainLeaks())
        return TRUE;

    if (this == NULL)
        return TRUE;

    if (IsAppDomainAgileRaw())
        return TRUE;

#ifndef _DEBUG
    MethodTable *pMT = GetGCSafeMethodTable();

    if (!pMT->IsDomainNeutral())
        return pAppDomain == pMT->GetDomain();
#endif

    ADIndex index = GetHeader()->GetAppDomainIndex();

    _ASSERTE(index.m_dwIndex != 0);

    return (pAppDomain != NULL && index == pAppDomain->GetIndex());
}
#endif

BOOL Object::IsTypeAppDomainAgile()
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    DEBUG_ONLY_FUNCTION;

    MethodTable *pMT = GetGCSafeMethodTable();

    if (pMT->IsArray())
    {
        TypeHandle th = pMT->GetApproxArrayElementTypeHandle();
        return th.IsArrayOfElementsAppDomainAgile();
    }
    else
        return pMT->GetClass()->IsAppDomainAgile();
}

BOOL Object::IsTypeCheckAppDomainAgile()
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    DEBUG_ONLY_FUNCTION;

    MethodTable *pMT = GetGCSafeMethodTable();

    if (pMT->IsArray())
    {
        TypeHandle th = pMT->GetApproxArrayElementTypeHandle();
        return th.IsArrayOfElementsCheckAppDomainAgile();
    }
    else
        return pMT->GetClass()->IsCheckAppDomainAgile();
}

BOOL Object::IsTypeNeverAppDomainAgile()
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    DEBUG_ONLY_FUNCTION;

    return !IsTypeAppDomainAgile() && !IsTypeCheckAppDomainAgile();
}

BOOL Object::IsTypeTypesafeAppDomainAgile()
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    DEBUG_ONLY_FUNCTION;

    return IsTypeAppDomainAgile() && !IsTypeCheckAppDomainAgile();
}

BOOL Object::TryAssignAppDomain(AppDomain *pAppDomain, BOOL raiseAssert)
{
    LIMITED_METHOD_CONTRACT;
    FAULT_NOT_FATAL();
    DEBUG_ONLY_FUNCTION;

    BOOL ret = TRUE;

    EX_TRY
    {
        ret = AssignAppDomain(pAppDomain,raiseAssert);
    }
    EX_CATCH{}
    EX_END_CATCH(SwallowAllExceptions);

    return ret;
}

BOOL Object::AssignAppDomain(AppDomain *pAppDomain, BOOL raiseAssert)
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;
    DEBUG_ONLY_FUNCTION;

    if (!g_pConfig->AppDomainLeaks())
        return TRUE;

    if (CheckAppDomain(pAppDomain))
        return TRUE;

    //
    // App domain does not match; try to make this object agile
    //

    if (IsTypeNeverAppDomainAgile())
    {
        if (raiseAssert)
        {
            if (pAppDomain == NULL)
                _ASSERTE(!"Attempt to reference a domain bound object from an agile location");
            else
                _ASSERTE(!"Attempt to reference a domain bound object from a different domain");
        }
        return FALSE;
    }
    else
    {
        //
        // Make object agile
        //

        if (! IsTypeAppDomainAgile() && ! SetFieldsAgile(raiseAssert))
        {
            SetIsCheckedForAppDomainAgile();
            return FALSE;
        }

        SetSyncBlockAppDomainAgile();

        return TRUE;        
    }
}

BOOL Object::AssignValueTypeAppDomain(MethodTable *pMT, void *base, AppDomain *pAppDomain, BOOL raiseAssert)
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;
    DEBUG_ONLY_FUNCTION;

    if (!g_pConfig->AppDomainLeaks())
        return TRUE;

    if (pMT->GetClass()->IsAppDomainAgile())
        return TRUE;

    if (pAppDomain == NULL)
    {
        //
        // Do not allow any object to be set to be agile unless we 
        // are compiling field access checking into the class.  This
        // will help guard against unintentional "agile" propagation
        // as well.
        //

        if (pMT->GetClass()->IsNeverAppDomainAgile())
        {
            _ASSERTE(!"Attempt to reference a domain bound object from an agile location");
            return FALSE;
        }

        return SetClassFieldsAgile(pMT, base, TRUE/*=baseIsVT*/, raiseAssert);
    }
    else
    {
        return ValidateClassFields(pMT, base, TRUE/*=baseIsVT*/, pAppDomain, raiseAssert);
    }
}

BOOL Object::SetFieldsAgile(BOOL raiseAssert, SetAppDomainAgilePendingTable *pTable)
{
    CONTRACTL
    {
        THROWS;
        GC_NOTRIGGER;
        INJECT_FAULT(COMPlusThrowOM(););
        DEBUG_ONLY;
    }
    CONTRACTL_END;

    BOOL result = TRUE;

    MethodTable *pMT= GetGCSafeMethodTable();

    if (pMT->IsArray())
    {
        switch (pMT->GetArrayElementType())
        {
        case ELEMENT_TYPE_CLASS:
        case ELEMENT_TYPE_ARRAY:
        case ELEMENT_TYPE_SZARRAY:
            {
                PtrArray *pArray = (PtrArray *) this;

                DWORD n = pArray->GetNumComponents();
                OBJECTREF *p = (OBJECTREF *) 
                  (((BYTE*)pArray) + ArrayBase::GetDataPtrOffset(GetGCSafeMethodTable()));

                for (DWORD i=0; i<n; i++)
                {
                    if (!p[i]->SetAppDomainAgile(raiseAssert, pTable))
                        result = FALSE;
                }

                break;
            }
        case ELEMENT_TYPE_VALUETYPE:
            {
                ArrayBase *pArray = (ArrayBase *) this;

                MethodTable *pElemMT = pMT->GetApproxArrayElementTypeHandle().GetMethodTable();

                BYTE *p = ((BYTE*)pArray) + ArrayBase::GetDataPtrOffset(GetGCSafeMethodTable());
                SIZE_T size = pArray->GetComponentSize();
                SIZE_T n = pArray->GetNumComponents();

                for (SIZE_T i=0; i<n; i++)
                    if (!SetClassFieldsAgile(pElemMT, p + i*size, TRUE/*=baseIsVT*/, raiseAssert, pTable))
                        result = FALSE;

                break;
            }
            
        default:
            _ASSERTE(!"Unexpected array type");
        }
    }
    else
    {
        if (pMT->GetClass()->IsNeverAppDomainAgile())
        {
            _ASSERTE(!"Attempt to reference a domain bound object from an agile location");
            return FALSE;
        }

        while (pMT != NULL && !pMT->GetClass()->IsTypesafeAppDomainAgile())
        {
            if (!SetClassFieldsAgile(pMT, this, FALSE/*=baseIsVT*/, raiseAssert, pTable))
                result = FALSE;

            pMT = pMT->GetParentMethodTable();

            if (pMT->GetClass()->IsNeverAppDomainAgile())
            {
                _ASSERTE(!"Attempt to reference a domain bound object from an agile location");
                return FALSE;
            }
        }
    }

    return result;
}

BOOL Object::SetClassFieldsAgile(MethodTable *pMT, void *base, BOOL baseIsVT, BOOL raiseAssert, SetAppDomainAgilePendingTable *pTable)
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;

    BOOL result = TRUE;

    if (pMT->GetClass()->IsNeverAppDomainAgile())
    {
        _ASSERTE(!"Attempt to reference a domain bound object from an agile location");
        return FALSE;
    }

    // This type approximation is OK since we are only checking some layout information 
    // and all compatible instantiations share the same GC characteristics
    ApproxFieldDescIterator fdIterator(pMT, ApproxFieldDescIterator::INSTANCE_FIELDS);
    FieldDesc* pField;

    while ((pField = fdIterator.Next()) != NULL)
    {
        if (pField->IsDangerousAppDomainAgileField())
        {
            if (pField->GetFieldType() == ELEMENT_TYPE_CLASS)
            {
                OBJECTREF ref;

                if (baseIsVT)
                    ref = *(OBJECTREF*) pField->GetAddressNoThrowNoGC(base);
                else
                    ref = *(OBJECTREF*) pField->GetAddressGuaranteedInHeap(base);

                if (ref != 0 && !ref->IsAppDomainAgile())
                {
                    if (!ref->SetAppDomainAgile(raiseAssert, pTable))
                        result = FALSE;
                }
            }
            else if (pField->GetFieldType() == ELEMENT_TYPE_VALUETYPE)
            {
                // Be careful here - we may not have loaded a value
                // type field of a class under prejit, and we don't
                // want to trigger class loading here.

                TypeHandle th = pField->LookupFieldTypeHandle();
                if (!th.IsNull())
                {
                    void *nestedBase;

                    if (baseIsVT)
                        nestedBase = pField->GetAddressNoThrowNoGC(base);
                    else
                        nestedBase = pField->GetAddressGuaranteedInHeap(base);

                    if (!SetClassFieldsAgile(th.GetMethodTable(),
                                             nestedBase,
                                             TRUE/*=baseIsVT*/,
                                             raiseAssert,
                                             pTable))
                    {
                        result = FALSE;
                    }
                }
            }
            else
            {
                _ASSERTE(!"Bad field type");
            }
        }
    }

    return result;
}

BOOL Object::ValidateAppDomain(AppDomain *pAppDomain)
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;


    if (!g_pConfig->AppDomainLeaks())
        return TRUE;

    if (this == NULL)
        return TRUE;

    if (CheckAppDomain())
        return ValidateAppDomainFields(pAppDomain);

    return AssignAppDomain(pAppDomain);
}

BOOL Object::ValidateAppDomainFields(AppDomain *pAppDomain)
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;

    BOOL result = TRUE;

    MethodTable *pMT = GetGCSafeMethodTable();

    while (pMT != NULL && !pMT->GetClass()->IsTypesafeAppDomainAgile())
    {
        if (!ValidateClassFields(pMT, this, FALSE/*=baseIsVT*/, pAppDomain))
            result = FALSE;

        pMT = pMT->GetParentMethodTable();
    }

    return result;
}

BOOL Object::ValidateValueTypeAppDomain(MethodTable *pMT, void *base, AppDomain *pAppDomain, BOOL raiseAssert)
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;

    if (!g_pConfig->AppDomainLeaks())
        return TRUE;

    if (pAppDomain == NULL)
    {
        if (pMT->GetClass()->IsTypesafeAppDomainAgile())
            return TRUE;
        else if (pMT->GetClass()->IsNeverAppDomainAgile())
        {
            if (raiseAssert)
                _ASSERTE(!"Value type cannot be app domain agile");
            return FALSE;
        }
    }

    return ValidateClassFields(pMT, base, TRUE/*=baseIsVT*/, pAppDomain, raiseAssert);
}

BOOL Object::ValidateClassFields(MethodTable *pMT, void *base, BOOL baseIsVT, AppDomain *pAppDomain, BOOL raiseAssert)
{
    STATIC_CONTRACT_THROWS;
    STATIC_CONTRACT_GC_NOTRIGGER;

    BOOL result = TRUE;

    // This type approximation is OK since we are only checking some layout information 
    // and all compatible instantiations share the same GC characteristics
    ApproxFieldDescIterator fdIterator(pMT, ApproxFieldDescIterator::INSTANCE_FIELDS);
    FieldDesc* pField;

    while ((pField = fdIterator.Next()) != NULL)
    {
        if (!pMT->GetClass()->IsCheckAppDomainAgile() 
            || pField->IsDangerousAppDomainAgileField())
        {
            if (pField->GetFieldType() == ELEMENT_TYPE_CLASS)
            {
                OBJECTREF ref;

                if (baseIsVT)
                    ref = ObjectToOBJECTREF(*(Object**) pField->GetAddressNoThrowNoGC(base));
                else
                    ref = ObjectToOBJECTREF(*(Object**) pField->GetAddressGuaranteedInHeap(base));

                if (ref != 0 && !ref->AssignAppDomain(pAppDomain, raiseAssert))
                    result = FALSE;
            }
            else if (pField->GetFieldType() == ELEMENT_TYPE_VALUETYPE)
            {
                // Be careful here - we may not have loaded a value
                // type field of a class under prejit, and we don't
                // want to trigger class loading here.

                TypeHandle th = pField->LookupFieldTypeHandle();
                if (!th.IsNull())
                {
                    void *nestedBase;

                    if (baseIsVT)
                        nestedBase = pField->GetAddressNoThrowNoGC(base);
                    else
                        nestedBase = pField->GetAddressGuaranteedInHeap(base);

                    if (!ValidateValueTypeAppDomain(th.GetMethodTable(),
                                                    nestedBase,
                                                    pAppDomain,
                                                    raiseAssert
                                                    ))
                        result = FALSE;

                }
            }
        }
    }

    return result;
}

#endif // CHECK_APP_DOMAIN_LEAKS

void Object::ValidatePromote(ScanContext *sc, DWORD flags)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;


#if defined (VERIFY_HEAP)
    Validate();
#endif

#if CHECK_APP_DOMAIN_LEAKS
    // Do app domain integrity checking here
    if (g_pConfig->AppDomainLeaks())
    {
        AppDomain *pDomain = GetAppDomain();

// This assert will incorrectly trip when
// InternalCrossContextCallback is on the stack.  InternalCrossContextCallback
// intentionally passes an object across domains on the same thread.
#if 0
        if (flags & GC_CALL_CHECK_APP_DOMAIN)
            _ASSERTE(TryAssignAppDomain(sc->pCurrentDomain));
#endif

        if ((flags & GC_CALL_CHECK_APP_DOMAIN)
            && pDomain != NULL 
            && !pDomain->ShouldHaveRoots() 
            && !TrySetAppDomainAgile(FALSE))    
        {
            _ASSERTE(!"Found GC object which should have been purged during app domain unload.");
        }
    }
#endif
}

void Object::ValidateHeap(Object *from, BOOL bDeep)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

#if defined (VERIFY_HEAP)
    //no need to verify next object's header in this case
    //since this is called in verify_heap, which will verfiy every object anyway
    Validate(bDeep, FALSE); 
#endif

#if CHECK_APP_DOMAIN_LEAKS
    // Do app domain integrity checking here
    if (g_pConfig->AppDomainLeaks() && bDeep)
    {
        AppDomain *pDomain = from->GetAppDomain();

        // 
        // Don't perform check if we're checking for agility, and the containing type is not
        // marked checked agile - this will cover "proxy" type agility 
        // where cross references are allowed
        //

        // Changed the GetMethodTable calls in this function to GetGCSafeMethodTable
        // because GC could use the mark bit to simulate a mark and can have it set during
        // verify heap (and would be cleared when verify heap is done). 
        // We'd get AV pretty soon anyway if it was truly mistakenly set.
        if (pDomain != NULL || from->GetGCSafeMethodTable()->GetClass()->IsCheckAppDomainAgile())
        {
            //special case:thread object is allowed to hold a context belonging to current domain
            if (from->GetGCSafeMethodTable() == g_pThreadClass && 
                      (
#ifdef FEATURE_REMOTING                      
                      this == OBJECTREFToObject(((ThreadBaseObject *)from)->m_ExposedContext) ||
#endif                      
#ifndef FEATURE_CORECLR
                        this == OBJECTREFToObject(((ThreadBaseObject *)from)->m_ExecutionContext) ||
#endif
                        false))
            {  
                if (((ThreadBaseObject *)from)->m_InternalThread)
                    _ASSERTE (CheckAppDomain (((ThreadBaseObject *)from)->m_InternalThread->GetDomain ()));
            }
            // special case: Overlapped has a field OverlappedData which may be moved to default domain
            // during AD unload
            else if (GetGCSafeMethodTable() == g_pOverlappedDataClass && 
                     GetAppDomainIndex() == SystemDomain::System()->DefaultDomain()->GetIndex())
            {
            }
            else
            {
                TryAssignAppDomain(pDomain);
            }
        }

        if (pDomain != NULL
            && !pDomain->ShouldHaveInstances() 
            && !TrySetAppDomainAgile(FALSE))
            _ASSERTE(!"Found GC object which should have been purged during app domain unload.");
    }
#endif
}

void Object::SetOffsetObjectRef(DWORD dwOffset, size_t dwValue)
{ 
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_MODE_COOPERATIVE;
    STATIC_CONTRACT_SO_TOLERANT;

    OBJECTREF*  location;
    OBJECTREF   o;

    location = (OBJECTREF *) &GetData()[dwOffset];
    o        = ObjectToOBJECTREF(*(Object **)  &dwValue);

    SetObjectReference( location, o, GetAppDomain() );
}

/******************************************************************/
/*
 * Write Barrier Helper
 *
 * Use this function to assign an object reference into
 * another object.
 *
 * It will set the appropriate GC Write Barrier data
 */

#if CHECK_APP_DOMAIN_LEAKS
void SetObjectReferenceChecked(OBJECTREF *dst,OBJECTREF ref,AppDomain *pAppDomain)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_MODE_COOPERATIVE;
    STATIC_CONTRACT_CANNOT_TAKE_LOCK;

    DEBUG_ONLY_FUNCTION;

    ref->TryAssignAppDomain(pAppDomain);
    return SetObjectReferenceUnchecked(dst,ref);
}
#endif

void SetObjectReferenceUnchecked(OBJECTREF *dst,OBJECTREF ref)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_MODE_COOPERATIVE;
    STATIC_CONTRACT_CANNOT_TAKE_LOCK;

    // Assign value. We use casting to avoid going thru the overloaded
    // OBJECTREF= operator which in this case would trigger a false
    // write-barrier violation assert.
    VolatileStore((Object**)dst, OBJECTREFToObject(ref));
#ifdef _DEBUG
    Thread::ObjectRefAssign(dst);
#endif
    ErectWriteBarrier(dst, ref);
}

/******************************************************************/
    // copies src to dest worrying about write barriers.  
    // Note that it can work on normal objects (but not arrays)
    // if dest, points just after the VTABLE.
#if CHECK_APP_DOMAIN_LEAKS
void CopyValueClassChecked(void* dest, void* src, MethodTable *pMT, AppDomain *pDomain)
{
    STATIC_CONTRACT_DEBUG_ONLY;
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_MODE_COOPERATIVE;

    DEBUG_ONLY_FUNCTION;

    FAULT_NOT_FATAL();
    EX_TRY
    {
        Object::AssignValueTypeAppDomain(pMT, src, pDomain);
    }
    EX_CATCH
    {
    }
    EX_END_CATCH(SwallowAllExceptions);
    CopyValueClassUnchecked(dest,src,pMT);
}

// Copy value class into the argument specified by the argDest, performing an appdomain check first.
// The destOffset is nonzero when copying values into Nullable<T>, it is the offset
// of the T value inside of the Nullable<T>
void CopyValueClassArgChecked(ArgDestination *argDest, void* src, MethodTable *pMT, AppDomain *pDomain, int destOffset)
{
    STATIC_CONTRACT_DEBUG_ONLY;
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_MODE_COOPERATIVE;

    DEBUG_ONLY_FUNCTION;

    FAULT_NOT_FATAL();
    EX_TRY
    {
        Object::AssignValueTypeAppDomain(pMT, src, pDomain);
    }
    EX_CATCH
    {
    }
    EX_END_CATCH(SwallowAllExceptions);
    CopyValueClassArgUnchecked(argDest, src, pMT, destOffset);
}
#endif
    
void STDCALL CopyValueClassUnchecked(void* dest, void* src, MethodTable *pMT) 
{

    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_MODE_COOPERATIVE;

    _ASSERTE(!pMT->IsArray());  // bunch of assumptions about arrays wrong. 

        // Copy the bulk of the data, and any non-GC refs. 
    switch (pMT->GetNumInstanceFieldBytes())
    {        
    case 1:
        VolatileStore((UINT8*)dest, *(UINT8*)src);
        break;
#ifndef ALIGN_ACCESS
        // we can hit an alignment fault if the value type has multiple 
        // smaller fields.  Example: if there are two I4 fields, the 
        // value class can be aligned to 4-byte boundaries, yet the 
        // NumInstanceFieldBytes is 8
    case 2:
        VolatileStore((UINT16*)dest, *(UINT16*)src);
        break;
    case 4:
        VolatileStore((UINT32*)dest, *(UINT32*)src);
        break;
    case 8:
        VolatileStore((UINT64*)dest, *(UINT64*)src);
        break;
#endif // !ALIGN_ACCESS
    default:
        memcpyNoGCRefs(dest, src, pMT->GetNumInstanceFieldBytes());
        break;
    }

        // Tell the GC about any copies.  
    if (pMT->ContainsPointers())
    {   
        CGCDesc* map = CGCDesc::GetCGCDescFromMT(pMT);
        CGCDescSeries* cur = map->GetHighestSeries();
        CGCDescSeries* last = map->GetLowestSeries();
        DWORD size = pMT->GetBaseSize();
        _ASSERTE(cur >= last);
        do                                                                  
        {   
            // offset to embedded references in this series must be
            // adjusted by the VTable pointer, when in the unboxed state.
            size_t offset = cur->GetSeriesOffset() - sizeof(void*);
            OBJECTREF* srcPtr = (OBJECTREF*)(((BYTE*) src) + offset);
            OBJECTREF* destPtr = (OBJECTREF*)(((BYTE*) dest) + offset);
            OBJECTREF* srcPtrStop = (OBJECTREF*)((BYTE*) srcPtr + cur->GetSeriesSize() + size);         
            while (srcPtr < srcPtrStop)                                         
            {   
                SetObjectReferenceUnchecked(destPtr, ObjectToOBJECTREF(*(Object**)srcPtr));
                srcPtr++;
                destPtr++;
            }                                                               
            cur--;                                                              
        } while (cur >= last);                                              
    }
}

// Copy value class into the argument specified by the argDest.
// The destOffset is nonzero when copying values into Nullable<T>, it is the offset
// of the T value inside of the Nullable<T>
void STDCALL CopyValueClassArgUnchecked(ArgDestination *argDest, void* src, MethodTable *pMT, int destOffset) 
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_MODE_COOPERATIVE;

#if defined(UNIX_AMD64_ABI) && defined(FEATURE_UNIX_AMD64_STRUCT_PASSING)

    if (argDest->IsStructPassedInRegs())
    {
        argDest->CopyStructToRegisters(src, pMT->GetNumInstanceFieldBytes(), destOffset);
        return;
    }

#endif // UNIX_AMD64_ABI && FEATURE_UNIX_AMD64_STRUCT_PASSING
    // destOffset is only valid for Nullable<T> passed in registers
    _ASSERTE(destOffset == 0);

    CopyValueClassUnchecked(argDest->GetDestinationAddress(), src, pMT);
}

// Initialize the value class argument to zeros
void InitValueClassArg(ArgDestination *argDest, MethodTable *pMT)
{ 
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_MODE_COOPERATIVE;

#if defined(UNIX_AMD64_ABI) && defined(FEATURE_UNIX_AMD64_STRUCT_PASSING)

    if (argDest->IsStructPassedInRegs())
    {
        argDest->ZeroStructInRegisters(pMT->GetNumInstanceFieldBytes());
        return;
    }

#endif    
    InitValueClass(argDest->GetDestinationAddress(), pMT);
}

#if defined (VERIFY_HEAP)

#include "dbginterface.h"

    // make the checking code goes as fast as possible!
#if defined(_MSC_VER)
#pragma optimize("tgy", on)
#endif

#define CREATE_CHECK_STRING(x) #x
#define CHECK_AND_TEAR_DOWN(x)                                      \
    do{                                                             \
        if (!(x))                                                   \
        {                                                           \
            _ASSERTE(!CREATE_CHECK_STRING(x));                      \
            EEPOLICY_HANDLE_FATAL_ERROR(COR_E_EXECUTIONENGINE);     \
        }                                                           \
    } while (0)

VOID Object::Validate(BOOL bDeep, BOOL bVerifyNextHeader, BOOL bVerifySyncBlock)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_MODE_COOPERATIVE;
    STATIC_CONTRACT_CANNOT_TAKE_LOCK;

    if (this == NULL)
    {
        return;     // NULL is ok
    }

    if (g_IBCLogger.InstrEnabled() && !GCStress<cfg_any>::IsEnabled())
    {
        // If we are instrumenting for IBC (and GCStress is not enabled)
        // then skip these Object::Validate() as they slow down the
        // instrument phase by an order of magnitude
        return;
    }

    if (g_fEEShutDown & ShutDown_Phase2)
    {
        // During second phase of shutdown the code below is not guaranteed to work.
        return;
    }

#ifdef _DEBUG
    {
        BEGIN_GETTHREAD_ALLOWED_IN_NO_THROW_REGION;
        Thread *pThread = GetThread();

        if (pThread != NULL && !(pThread->PreemptiveGCDisabled()))
        {
            // Debugger helper threads are special in that they take over for
            // what would normally be a nonEE thread (the RCThread).  If an
            // EE thread is doing RCThread duty, then it should be treated
            // as such.
            //
            // There are some GC threads in the same kind of category.  Note that
            // GetThread() sometimes returns them, if DLL_THREAD_ATTACH notifications
            // have run some managed code.
            if (!dbgOnly_IsSpecialEEThread() && !IsGCSpecialThread())
                _ASSERTE(!"OBJECTREF being accessed while thread is in preemptive GC mode.");
        }
        END_GETTHREAD_ALLOWED_IN_NO_THROW_REGION;
    }
#endif


    {   // ValidateInner can throw or fault on failure which violates contract.
        CONTRACT_VIOLATION(ThrowsViolation | FaultViolation);

        // using inner helper because of TRY and stack objects with destructors.
        ValidateInner(bDeep, bVerifyNextHeader, bVerifySyncBlock);
    }
}

VOID Object::ValidateInner(BOOL bDeep, BOOL bVerifyNextHeader, BOOL bVerifySyncBlock)
{
    STATIC_CONTRACT_THROWS; // See CONTRACT_VIOLATION above
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FAULT; // See CONTRACT_VIOLATION above
    STATIC_CONTRACT_MODE_COOPERATIVE;
    STATIC_CONTRACT_CANNOT_TAKE_LOCK;

    int lastTest = 0;

    EX_TRY
    {
        // in order to avoid contract violations in the EH code we'll allow AVs here, 
        // they'll be handled in the catch block
        AVInRuntimeImplOkayHolder avOk;

        MethodTable *pMT = GetGCSafeMethodTable();
        lastTest = 1;

        CHECK_AND_TEAR_DOWN(pMT->Validate());
        lastTest = 2;

        bool noRangeChecks =
            (g_pConfig->GetHeapVerifyLevel() & EEConfig::HEAPVERIFY_NO_RANGE_CHECKS) == EEConfig::HEAPVERIFY_NO_RANGE_CHECKS;

        // noRangeChecks depends on initial values being FALSE
        BOOL bSmallObjectHeapPtr = FALSE, bLargeObjectHeapPtr = FALSE;
        if (!noRangeChecks)
        {
            bSmallObjectHeapPtr = GCHeap::GetGCHeap()->IsHeapPointer(this, TRUE);
            if (!bSmallObjectHeapPtr)
                bLargeObjectHeapPtr = GCHeap::GetGCHeap()->IsHeapPointer(this);
                
            CHECK_AND_TEAR_DOWN(bSmallObjectHeapPtr || bLargeObjectHeapPtr);
        }

        lastTest = 3;

        if (bDeep)
        {
            CHECK_AND_TEAR_DOWN(GetHeader()->Validate(bVerifySyncBlock));
        }
        
        lastTest = 4;

        if (bDeep && (g_pConfig->GetHeapVerifyLevel() & EEConfig::HEAPVERIFY_GC)) {
            GCHeap::GetGCHeap()->ValidateObjectMember(this);
        }

        lastTest = 5;

        // since bSmallObjectHeapPtr is initialized to FALSE
        // we skip checking noRangeChecks since if skipping
        // is enabled bSmallObjectHeapPtr will always be false.
        if (bSmallObjectHeapPtr) {
            CHECK_AND_TEAR_DOWN(!GCHeap::GetGCHeap()->IsObjectInFixedHeap(this));
        }

        lastTest = 6;

#if CHECK_APP_DOMAIN_LEAKS
        // when it's not safe to verify the fields, it's not safe to verify AppDomain either
        // because the process might try to access fields.
        if (bDeep && g_pConfig->AppDomainLeaks())
        {
            //
            // Check to see that our domain is valid.  This will assert if it has been unloaded.
            //
            SCAN_IGNORE_FAULT;
            GetAppDomain();
        }        
#endif

        lastTest = 7;

        // try to validate next object's header
        if (bDeep 
            && bVerifyNextHeader 
            && GCScan::GetGcRuntimeStructuresValid ()
            //NextObj could be very slow if concurrent GC is going on
            && !(GCHeap::IsGCHeapInitialized() && GCHeap::GetGCHeap ()->IsConcurrentGCInProgress ()))
        {
            Object * nextObj = GCHeap::GetGCHeap ()->NextObj (this);
            if ((nextObj != NULL) &&
                (nextObj->GetGCSafeMethodTable() != g_pFreeObjectMethodTable))
            {
                CHECK_AND_TEAR_DOWN(nextObj->GetHeader()->Validate(FALSE));
            }
        }

        lastTest = 8;

#ifdef FEATURE_64BIT_ALIGNMENT
        if (pMT->RequiresAlign8())
        {
            CHECK_AND_TEAR_DOWN((((size_t)this) & 0x7) == (pMT->IsValueType()? 4:0));
        }
        lastTest = 9;
#endif // FEATURE_64BIT_ALIGNMENT

    }
    EX_CATCH
    {
        STRESS_LOG3(LF_ASSERT, LL_ALWAYS, "Detected use of corrupted OBJECTREF: %p [MT=%p] (lastTest=%d)", this, lastTest > 0 ? (*(size_t*)this) : 0, lastTest);
        CHECK_AND_TEAR_DOWN(!"Detected use of a corrupted OBJECTREF. Possible GC hole.");
    }
    EX_END_CATCH(SwallowAllExceptions);
}


#endif   // VERIFY_HEAP

/*==================================NewString===================================
**Action:  Creates a System.String object.
**Returns:
**Arguments:
**Exceptions:
==============================================================================*/
STRINGREF StringObject::NewString(INT32 length) {
    CONTRACTL {
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        PRECONDITION(length>=0);
    } CONTRACTL_END;

    STRINGREF pString;

    if (length<0) {
        return NULL;
    } else if (length == 0) {
        return GetEmptyString();
    } else {
        pString = AllocateString(length);
        _ASSERTE(pString->GetBuffer()[length] == 0);

        return pString;
    }
}


/*==================================NewString===================================
**Action: Many years ago, VB didn't have the concept of a byte array, so enterprising
**        users created one by allocating a BSTR with an odd length and using it to
**        store bytes.  A generation later, we're still stuck supporting this behavior.
**        The way that we do this is to take advantage of the difference between the
**        array length and the string length.  The string length will always be the
**        number of characters between the start of the string and the terminating 0.
**        If we need an odd number of bytes, we'll take one wchar after the terminating 0.
**        (e.g. at position StringLength+1).  The high-order byte of this wchar is
**        reserved for flags and the low-order byte is our odd byte. This function is
**        used to allocate a string of that shape, but we don't actually mark the
**        trailing byte as being in use yet.
**Returns: A newly allocated string.  Null if length is less than 0.
**Arguments: length -- the length of the string to allocate
**           bHasTrailByte -- whether the string also has a trailing byte.
**Exceptions: OutOfMemoryException if AllocateString fails.
==============================================================================*/
STRINGREF StringObject::NewString(INT32 length, BOOL bHasTrailByte) {
    CONTRACTL {
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        PRECONDITION(length>=0 && length != INT32_MAX);
    } CONTRACTL_END;

    STRINGREF pString;
    if (length<0 || length == INT32_MAX) {
        return NULL;
    } else if (length == 0) {
        return GetEmptyString();
    } else {
        pString = AllocateString(length);
        _ASSERTE(pString->GetBuffer()[length]==0);
        if (bHasTrailByte) {
            _ASSERTE(pString->GetBuffer()[length+1]==0);
        }
    }

    return pString;
}

//========================================================================
// Creates a System.String object and initializes from
// the supplied null-terminated C string.
//
// Maps NULL to null. This function does *not* return null to indicate
// error situations: it throws an exception instead.
//========================================================================
STRINGREF StringObject::NewString(const WCHAR *pwsz)
{
    CONTRACTL {
        GC_TRIGGERS;
        MODE_COOPERATIVE;
    } CONTRACTL_END;

    if (!pwsz)
    {
        return NULL;
    }
    else
    {

        DWORD nch = (DWORD)wcslen(pwsz);
        if (nch==0) {
            return GetEmptyString();
        }

#if 0        
        //        
        // This assert is disabled because it is valid for us to get a 
        // pointer from the gc heap here as long as it is pinned.  This
        // can happen when a string is marshalled to unmanaged by 
        // pinning and then later put into a struct and that struct is
        // then marshalled to managed.  
        //
        _ASSERTE(!GCHeap::GetGCHeap()->IsHeapPointer((BYTE *) pwsz) ||
                 !"pwsz can not point to GC Heap");
#endif // 0

        STRINGREF pString = AllocateString( nch );

        memcpyNoGCRefs(pString->GetBuffer(), pwsz, nch*sizeof(WCHAR));
        _ASSERTE(pString->GetBuffer()[nch] == 0);
        return pString;
    }
}

#if defined(_MSC_VER) && defined(_TARGET_X86_)
#pragma optimize("y", on)        // Small critical routines, don't put in EBP frame 
#endif

STRINGREF StringObject::NewString(const WCHAR *pwsz, int length) {
    CONTRACTL {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        PRECONDITION(length>=0);
    } CONTRACTL_END;

    if (!pwsz)
    {
        return NULL;
    }
    else if (length <= 0) {
        return GetEmptyString();
    } else {
#if 0        
        //        
        // This assert is disabled because it is valid for us to get a 
        // pointer from the gc heap here as long as it is pinned.  This
        // can happen when a string is marshalled to unmanaged by 
        // pinning and then later put into a struct and that struct is
        // then marshalled to managed.  
        //
        _ASSERTE(!GCHeap::GetGCHeap()->IsHeapPointer((BYTE *) pwsz) ||
                 !"pwsz can not point to GC Heap");
#endif // 0
        STRINGREF pString = AllocateString(length);

        memcpyNoGCRefs(pString->GetBuffer(), pwsz, length*sizeof(WCHAR));
        _ASSERTE(pString->GetBuffer()[length] == 0);
        return pString;
    }
}

#if defined(_MSC_VER) && defined(_TARGET_X86_)
#pragma optimize("", on)        // Go back to command line default optimizations
#endif

STRINGREF StringObject::NewString(LPCUTF8 psz)
{
    CONTRACTL {
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        THROWS;
        PRECONDITION(CheckPointer(psz));
    } CONTRACTL_END;

    int length = (int)strlen(psz);
    if (length == 0) {
        return GetEmptyString();
    }
    CQuickBytes qb;
    WCHAR* pwsz = (WCHAR*) qb.AllocThrows((length) * sizeof(WCHAR));
    length = WszMultiByteToWideChar(CP_UTF8, 0, psz, length, pwsz, length);
    if (length == 0) {
        COMPlusThrow(kArgumentException, W("Arg_InvalidUTF8String"));
    }
    return NewString(pwsz, length);
}

STRINGREF StringObject::NewString(LPCUTF8 psz, int cBytes)
{
    CONTRACTL {
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        THROWS;
        PRECONDITION(CheckPointer(psz, NULL_OK));
    } CONTRACTL_END;

    if (!psz)
        return NULL;

    _ASSERTE(psz);
    _ASSERTE(cBytes >= 0);
    if (cBytes == 0) {
        return GetEmptyString();
    }
    int cWszBytes = 0;
    if (!ClrSafeInt<int>::multiply(cBytes, sizeof(WCHAR), cWszBytes))
        COMPlusThrowOM();
    CQuickBytes qb;
    WCHAR* pwsz = (WCHAR*) qb.AllocThrows(cWszBytes);
    int length = WszMultiByteToWideChar(CP_UTF8, 0, psz, cBytes, pwsz, cBytes);
    if (length == 0) {
        COMPlusThrow(kArgumentException, W("Arg_InvalidUTF8String"));
    }
    return NewString(pwsz, length);
}

//
//
// STATIC MEMBER VARIABLES
//
//
STRINGREF* StringObject::EmptyStringRefPtr=NULL;

//The special string helpers are used as flag bits for weird strings that have bytes
//after the terminating 0.  The only case where we use this right now is the VB BSTR as
//byte array which is described in MakeStringAsByteArrayFromBytes.
#define SPECIAL_STRING_VB_BYTE_ARRAY 0x100

FORCEINLINE BOOL MARKS_VB_BYTE_ARRAY(WCHAR x)
{
    return static_cast<BOOL>(x & SPECIAL_STRING_VB_BYTE_ARRAY);
}

FORCEINLINE WCHAR MAKE_VB_TRAIL_BYTE(BYTE x)
{
    return static_cast<WCHAR>(x) | SPECIAL_STRING_VB_BYTE_ARRAY;
}

FORCEINLINE BYTE GET_VB_TRAIL_BYTE(WCHAR x)
{
    return static_cast<BYTE>(x & 0xFF);
}


/*==============================InitEmptyStringRefPtr============================
**Action:  Gets an empty string refptr, cache the result.
**Returns: The retrieved STRINGREF.
==============================================================================*/
STRINGREF* StringObject::InitEmptyStringRefPtr() {
    CONTRACTL {
        THROWS;
        MODE_ANY;
        GC_TRIGGERS;
    } CONTRACTL_END;

    GCX_COOP();

    EEStringData data(0, W(""), TRUE);
    EmptyStringRefPtr = SystemDomain::System()->DefaultDomain()->GetLoaderAllocator()->GetStringObjRefPtrFromUnicodeString(&data);
    return EmptyStringRefPtr;
}

/*=============================StringInitCharHelper=============================
**Action:
**Returns:
**Arguments:
**Exceptions:
**Note this
==============================================================================*/
STRINGREF __stdcall StringObject::StringInitCharHelper(LPCSTR pszSource, int length) {
    CONTRACTL {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
    } CONTRACTL_END;

    STRINGREF pString=NULL;
    int dwSizeRequired=0;
     _ASSERTE(length>=-1);                        
     
    if (!pszSource || length == 0) {
        return StringObject::GetEmptyString();
    }
    else if ((size_t)pszSource < 64000) {
        COMPlusThrow(kArgumentException, W("Arg_MustBeStringPtrNotAtom"));
    }    

    // Make sure we can read from the pointer.
    // This is better than try to read from the pointer and catch the access violation exceptions.
    if( length == -1) {
        length = (INT32)strlen(pszSource);
    }
   
    if(length > 0)  {  
        dwSizeRequired=WszMultiByteToWideChar(CP_ACP, MB_PRECOMPOSED, pszSource, length, NULL, 0);
    }

    if (dwSizeRequired == 0) {
        if (length == 0) {
            return StringObject::GetEmptyString();
        }
        COMPlusThrow(kArgumentException, W("Arg_InvalidANSIString"));
    }

    pString = AllocateString(dwSizeRequired);        
    dwSizeRequired = WszMultiByteToWideChar(CP_ACP, MB_PRECOMPOSED, (LPCSTR)pszSource, length, pString->GetBuffer(), dwSizeRequired);
    if (dwSizeRequired == 0) {
        COMPlusThrow(kArgumentException, W("Arg_InvalidANSIString"));
    }

    _ASSERTE(dwSizeRequired != INT32_MAX && pString->GetBuffer()[dwSizeRequired]==0);

    return pString;
}


// strAChars must be null-terminated, with an appropriate aLength
// strBChars must be null-terminated, with an appropriate bLength OR bLength == -1
// If bLength == -1, we stop on the first null character in strBChars
BOOL StringObject::CaseInsensitiveCompHelper(__in_ecount(aLength) WCHAR *strAChars, __in_z INT8 *strBChars, INT32 aLength, INT32 bLength, INT32 *result) {
    CONTRACTL {
        NOTHROW;
        GC_NOTRIGGER;
        MODE_ANY;
        PRECONDITION(CheckPointer(strAChars));
        PRECONDITION(CheckPointer(strBChars));
        PRECONDITION(CheckPointer(result));
        SO_TOLERANT;
    } CONTRACTL_END;

    WCHAR *strAStart = strAChars;
    INT8  *strBStart = strBChars;
    unsigned charA;
    unsigned charB;

    for(;;) {        
        charA = *strAChars;
        charB = (unsigned) *strBChars;

        //Case-insensitive comparison on chars greater than 0x7F
        //requires a locale-aware casing operation and we're not going there.
        if ((charA|charB)>0x7F) {
            *result = 0;
            return FALSE;
        }

        // uppercase both chars. 
        if (charA>='a' && charA<='z') {
            charA ^= 0x20;
        } 
        if (charB>='a' && charB<='z') {
            charB ^= 0x20;
        }

        //Return the (case-insensitive) difference between them.
        if (charA!=charB) {
            *result = (int)(charA-charB);
            return TRUE;
        }


        if (charA==0)   // both strings have null character
        {
            if (bLength == -1)
            {
                *result = aLength - static_cast<INT32>(strAChars - strAStart); 
                return TRUE;
            }
            if (strAChars==strAStart + aLength || strBChars==strBStart + bLength)
            {
                *result = aLength - bLength; 
                return TRUE;
            }
            // else both embedded zeros
        } 

        // Next char
        strAChars++; strBChars++;
    }
    
}

INT32 StringObject::FastCompareStringHelper(DWORD* strAChars, INT32 countA, DWORD* strBChars, INT32 countB)
{
    STATIC_CONTRACT_SO_TOLERANT;
    
    INT32 count    = (countA < countB) ? countA : countB;

    PREFIX_ASSUME(count >= 0);    

    ptrdiff_t diff = (char *)strAChars - (char *)strBChars;

#if defined(_WIN64) || defined(ALIGN_ACCESS)
    int alignmentA = ((SIZE_T)strAChars) & (sizeof(SIZE_T) - 1);
    int alignmentB = ((SIZE_T)strBChars) & (sizeof(SIZE_T) - 1);
#endif // _WIN64 || ALIGN_ACCESS

#if defined(_WIN64)
    if (alignmentA == alignmentB)
    {
        if ((alignmentA == 2 || alignmentA == 6) && (count >= 1))
        {
            LPWSTR ptr2 = (WCHAR *)strBChars;

            if (( *((WCHAR*)((char *)ptr2 + diff)) - *ptr2) != 0)
            {
                return ((int)*((WCHAR*)((char *)ptr2 + diff)) - (int)*ptr2);
            }
            strBChars = (DWORD*)(++ptr2);
            count -= 1;
            alignmentA = (alignmentA == 2 ? 4 : 0);
        }

        if ((alignmentA == 4) && (count >= 2))
        {
            DWORD* ptr2 = (DWORD*)strBChars;

            if (( *((DWORD*)((char *)ptr2 + diff)) - *ptr2) != 0)
            {
                LPWSTR chkptr1 = (WCHAR*)((char *)strBChars + diff);
                LPWSTR chkptr2 = (WCHAR*)strBChars;

                if (*chkptr1 != *chkptr2)
                {
                    return ((int)*chkptr1 - (int)*chkptr2);
                }
                return ((int)*(chkptr1+1) - (int)*(chkptr2+1));
            }
            strBChars = ++ptr2;
            count -= 2;
            alignmentA = 0;
        }

        if (alignmentA == 0)
        {
            while (count >= 4)
            {
                SIZE_T* ptr2 = (SIZE_T*)strBChars;

                if (( *((SIZE_T*)((char *)ptr2 + diff)) - *ptr2) != 0)
                {
                    if (( *((DWORD*)((char *)ptr2 + diff)) - *(DWORD*)ptr2) != 0)
                    {
                        LPWSTR chkptr1 = (WCHAR*)((char *)strBChars + diff);
                        LPWSTR chkptr2 = (WCHAR*)strBChars;

                        if (*chkptr1 != *chkptr2)
                        {
                            return ((int)*chkptr1 - (int)*chkptr2);
                        }
                        return ((int)*(chkptr1+1) - (int)*(chkptr2+1));
                    }
                    else
                    {
                        LPWSTR chkptr1 = (WCHAR*)((DWORD*)((char *)strBChars + diff) + 1);
                        LPWSTR chkptr2 = (WCHAR*)((DWORD*)strBChars + 1);

                        if (*chkptr1 != *chkptr2)
                        {
                            return ((int)*chkptr1 - (int)*chkptr2);
                        }
                        return ((int)*(chkptr1+1) - (int)*(chkptr2+1));
                    }
                }
                strBChars = (DWORD*)(++ptr2);
                count -= 4;
            }
        }

        LPWSTR ptr2 = (WCHAR*)strBChars;
        while ((count -= 1) >= 0)
        {
            if (( *((WCHAR*)((char *)ptr2 + diff)) - *ptr2) != 0)
            {
                return ((int)*((WCHAR*)((char *)ptr2 + diff)) - (int)*ptr2);
            }
            ++ptr2;
        }
    }
    else
#endif // _WIN64
#if defined(ALIGN_ACCESS)
    if ( ( !IS_ALIGNED((size_t)strAChars, sizeof(DWORD)) || 
           !IS_ALIGNED((size_t)strBChars, sizeof(DWORD)) )  && 
         (abs(alignmentA - alignmentB) != 4) )
    {
        _ASSERTE(IS_ALIGNED((size_t)strAChars, sizeof(WCHAR)));
        _ASSERTE(IS_ALIGNED((size_t)strBChars, sizeof(WCHAR)));
        LPWSTR ptr2 = (WCHAR *)strBChars;

        while ((count -= 1) >= 0)
        {
            if (( *((WCHAR*)((char *)ptr2 + diff)) - *ptr2) != 0)
            {
                return ((int)*((WCHAR*)((char *)ptr2 + diff)) - (int)*ptr2);
            }
            ++ptr2;
        }
    }
    else
#endif // ALIGN_ACCESS
    {
#if defined(_WIN64) || defined(ALIGN_ACCESS)
        if (abs(alignmentA - alignmentB) == 4)
        {
            if ((alignmentA == 2) || (alignmentB == 2))
            {
                LPWSTR ptr2 = (WCHAR *)strBChars;

                if (( *((WCHAR*)((char *)ptr2 + diff)) - *ptr2) != 0)
                {
                    return ((int)*((WCHAR*)((char *)ptr2 + diff)) - (int)*ptr2);
                }
                strBChars = (DWORD*)(++ptr2);
                count -= 1;
            }
        }
#endif // WIN64 || ALIGN_ACCESS

        // Loop comparing a DWORD at a time.
        while ((count -= 2) >= 0)
        {
            if ((*((DWORD* )((char *)strBChars + diff)) - *strBChars) != 0)
            {
                LPWSTR ptr1 = (WCHAR*)((char *)strBChars + diff);
                LPWSTR ptr2 = (WCHAR*)strBChars;
                if (*ptr1 != *ptr2) {
                    return ((int)*ptr1 - (int)*ptr2);
                }
                return ((int)*(ptr1+1) - (int)*(ptr2+1));
            }
            ++strBChars;
        }

        int c;
        if (count == -1)
            if ((c = *((WCHAR *) ((char *)strBChars + diff)) - *((WCHAR *) strBChars)) != 0)
                return c;
    }

    return countA - countB;
}


/*=============================InternalHasHighChars=============================
**Action:  Checks if the string can be sorted quickly.  The requirements are that
**         the string contain no character greater than 0x80 and that the string not
**         contain an apostrophe or a hypen.  Apostrophe and hyphen are excluded so that
**         words like co-op and coop sort together.
**Returns: Void.  The side effect is to set a bit on the string indicating whether or not
**         the string contains high chars.
**Arguments: The String to be checked.
**Exceptions: None
==============================================================================*/
DWORD StringObject::InternalCheckHighChars() {
    WRAPPER_NO_CONTRACT;

    WCHAR *chars;
    WCHAR c;
    INT32 length;

    RefInterpretGetStringValuesDangerousForGC((WCHAR **) &chars, &length);

    DWORD stringState = STRING_STATE_FAST_OPS;

    for (int i=0; i<length; i++) {
        c = chars[i];
        if (c>=0x80) {
            SetHighCharState(STRING_STATE_HIGH_CHARS);
            return STRING_STATE_HIGH_CHARS;
        } else if (HighCharHelper::IsHighChar((int)c)) {
            //This means that we have a character which forces special sorting,
            //but doesn't necessarily force slower casing and indexing.  We'll
            //set a value to remember this, but we need to check the rest of
            //the string because we may still find a charcter greater than 0x7f.
            stringState = STRING_STATE_SPECIAL_SORT;
        }
    }

    SetHighCharState(stringState);
    return stringState;
}

#ifdef VERIFY_HEAP
/*=============================ValidateHighChars=============================
**Action:  Validate if the HighChars bits is set correctly, no side effect
**Returns: BOOL for result of validation
**Arguments: The String to be checked.
**Exceptions: None
==============================================================================*/
BOOL StringObject::ValidateHighChars()
{
    WRAPPER_NO_CONTRACT;
    DWORD curStringState = GetHighCharState ();
    // state could always be undetermined
    if (curStringState == STRING_STATE_UNDETERMINED)
    {
        return TRUE;
    }

    WCHAR *chars;
    INT32 length;
    RefInterpretGetStringValuesDangerousForGC((WCHAR **) &chars, &length);

    DWORD stringState = STRING_STATE_FAST_OPS;
    for (int i=0; i<length; i++) {
        WCHAR c = chars[i];
        if (c>=0x80) 
        {
            // if there is a high char in the string, the state has to be STRING_STATE_HIGH_CHARS
            return curStringState == STRING_STATE_HIGH_CHARS;
        } 
        else if (HighCharHelper::IsHighChar((int)c)) {
            //This means that we have a character which forces special sorting,
            //but doesn't necessarily force slower casing and indexing.  We'll
            //set a value to remember this, but we need to check the rest of
            //the string because we may still find a charcter greater than 0x7f.
            stringState = STRING_STATE_SPECIAL_SORT;
        }
    }
    
    return stringState == curStringState;
}

#endif //VERIFY_HEAP

/*============================InternalTrailByteCheck============================
**Action: Many years ago, VB didn't have the concept of a byte array, so enterprising
**        users created one by allocating a BSTR with an odd length and using it to
**        store bytes.  A generation later, we're still stuck supporting this behavior.
**        The way that we do this is stick the trail byte in the sync block
**        whenever we encounter such a situation. Since we expect this to be a very corner case
**        accessing the sync block seems like a good enough solution
**
**Returns: True if <CODE>str</CODE> contains a VB trail byte, false otherwise.
**Arguments: str -- The string to be examined.
**Exceptions: None
==============================================================================*/
BOOL StringObject::HasTrailByte() {
    WRAPPER_NO_CONTRACT;
    STATIC_CONTRACT_SO_TOLERANT;
    
    SyncBlock * pSyncBlock = PassiveGetSyncBlock();
    if(pSyncBlock != NULL)
    {
        return pSyncBlock->HasCOMBstrTrailByte();
    }

    return FALSE;
}

/*=================================GetTrailByte=================================
**Action:  If <CODE>str</CODE> contains a vb trail byte, returns a copy of it.
**Returns: True if <CODE>str</CODE> contains a trail byte.  *bTrailByte is set to
**         the byte in question if <CODE>str</CODE> does have a trail byte, otherwise
**         it's set to 0.
**Arguments: str -- The string being examined.
**           bTrailByte -- An out param to hold the value of the trail byte.
**Exceptions: None.
==============================================================================*/
BOOL StringObject::GetTrailByte(BYTE *bTrailByte) {
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        SO_TOLERANT;
        MODE_ANY;
    }
    CONTRACTL_END;
    _ASSERTE(bTrailByte);
    *bTrailByte=0;

    BOOL retValue = HasTrailByte();

    if(retValue)
    {
        *bTrailByte = GET_VB_TRAIL_BYTE(GetHeader()->PassiveGetSyncBlock()->GetCOMBstrTrailByte());
    }

    return retValue;
}

/*=================================SetTrailByte=================================
**Action: Sets the trail byte in the sync block
**Returns: True.
**Arguments: str -- The string into which to set the trail byte.
**           bTrailByte -- The trail byte to be added to the string.
**Exceptions: None.
==============================================================================*/
BOOL StringObject::SetTrailByte(BYTE bTrailByte) {
    WRAPPER_NO_CONTRACT;

    GetHeader()->GetSyncBlock()->SetCOMBstrTrailByte(MAKE_VB_TRAIL_BYTE(bTrailByte));
    return TRUE;
}


#define DEFAULT_CAPACITY 16
#define DEFAULT_MAX_CAPACITY 0x7FFFFFFF

/*================================ReplaceBuffer=================================
**This is a helper function designed to be used by N/Direct it replaces the entire
**contents of the String with a new string created by some native method.  This 
**will not be exposed through the StringBuilder class.
==============================================================================*/
void StringBufferObject::ReplaceBuffer(STRINGBUFFERREF *thisRef, __in_ecount(newLength) WCHAR *newBuffer, INT32 newLength) {
    CONTRACTL {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        PRECONDITION(CheckPointer(newBuffer));
        PRECONDITION(newLength>=0);
        PRECONDITION(CheckPointer(thisRef));
        PRECONDITION(IsProtectedByGCFrame(thisRef));
    } CONTRACTL_END;

    if(newLength > (*thisRef)->GetMaxCapacity())
    {
        COMPlusThrowArgumentOutOfRange(W("capacity"), W("ArgumentOutOfRange_Capacity"));
    }

    CHARARRAYREF newCharArray = AllocateCharArray((*thisRef)->GetAllocationLength(newLength+1));
    (*thisRef)->ReplaceBuffer(&newCharArray, newBuffer, newLength);
}


/*================================ReplaceBufferAnsi=================================
**This is a helper function designed to be used by N/Direct it replaces the entire
**contents of the String with a new string created by some native method.  This 
**will not be exposed through the StringBuilder class.
**
**This version does Ansi->Unicode conversion along the way. Although
**making it a member of COMStringBuffer exposes more stringbuffer internals
**than necessary, it does avoid requiring a temporary buffer to hold
**the Ansi->Unicode conversion.
==============================================================================*/
void StringBufferObject::ReplaceBufferAnsi(STRINGBUFFERREF *thisRef, __in_ecount(newCapacity) CHAR *newBuffer, INT32 newCapacity) {
    CONTRACTL {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        PRECONDITION(CheckPointer(newBuffer));
        PRECONDITION(CheckPointer(thisRef));
        PRECONDITION(IsProtectedByGCFrame(thisRef));
        PRECONDITION(newCapacity>=0);
    } CONTRACTL_END;

    if(newCapacity > (*thisRef)->GetMaxCapacity())
    {
        COMPlusThrowArgumentOutOfRange(W("capacity"), W("ArgumentOutOfRange_Capacity"));
    }

    CHARARRAYREF newCharArray = AllocateCharArray((*thisRef)->GetAllocationLength(newCapacity+1));
    (*thisRef)->ReplaceBufferWithAnsi(&newCharArray, newBuffer, newCapacity);
}


/*==============================LocalIndexOfString==============================
**Finds search within base and returns the index where it was found.  The search
**starts from startPos and we return -1 if search isn't found.  This is a direct 
**copy from COMString::IndexOfString, but doesn't require that we build up
**an instance of indexOfStringArgs before calling it.  
**
**Args:
**base -- the string in which to search
**search -- the string for which to search
**strLength -- the length of base
**patternLength -- the length of search
**startPos -- the place from which to start searching.
**
==============================================================================*/
/* static */ INT32 StringBufferObject::LocalIndexOfString(__in_ecount(strLength) WCHAR *base, __in_ecount(patternLength) WCHAR *search, int strLength, int patternLength, int startPos) {
    LIMITED_METHOD_CONTRACT
    _ASSERTE(base != NULL);
    _ASSERTE(search != NULL);

    int iThis, iPattern;
    for (iThis=startPos; iThis < (strLength-patternLength+1); iThis++) {
        for (iPattern=0; iPattern<patternLength && base[iThis+iPattern]==search[iPattern]; iPattern++);
        if (iPattern == patternLength) return iThis;
    }
    return -1;
}


#ifdef USE_CHECKED_OBJECTREFS

//-------------------------------------------------------------
// Default constructor, for non-initializing declarations:
//
//      OBJECTREF or;
//-------------------------------------------------------------
OBJECTREF::OBJECTREF()
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

    STATIC_CONTRACT_VIOLATION(SOToleranceViolation);

    m_asObj = (Object*)POISONC;
    Thread::ObjectRefNew(this);
}

//-------------------------------------------------------------
// Copy constructor, for passing OBJECTREF's as function arguments.
//-------------------------------------------------------------
OBJECTREF::OBJECTREF(const OBJECTREF & objref)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_MODE_COOPERATIVE;
    STATIC_CONTRACT_FORBID_FAULT;

    STATIC_CONTRACT_VIOLATION(SOToleranceViolation);

    VALIDATEOBJECT(objref.m_asObj);

    // !!! If this assert is fired, there are two possibilities:
    // !!! 1.  You are doing a type cast, e.g.  *(OBJECTREF*)pObj
    // !!!     Instead, you should use ObjectToOBJECTREF(*(Object**)pObj),
    // !!!                          or ObjectToSTRINGREF(*(StringObject**)pObj)
    // !!! 2.  There is a real GC hole here.
    // !!! Either way you need to fix the code.
    _ASSERTE(Thread::IsObjRefValid(&objref));
    if ((objref.m_asObj != 0) &&
        ((GCHeap*)GCHeap::GetGCHeap())->IsHeapPointer( (BYTE*)this ))
    {
        _ASSERTE(!"Write Barrier violation. Must use SetObjectReference() to assign OBJECTREF's into the GC heap!");
    }
    m_asObj = objref.m_asObj;
    
    if (m_asObj != 0) {
        ENABLESTRESSHEAP();
    }

    Thread::ObjectRefNew(this);
}


//-------------------------------------------------------------
// To allow NULL to be used as an OBJECTREF.
//-------------------------------------------------------------
OBJECTREF::OBJECTREF(TADDR nul)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

    STATIC_CONTRACT_VIOLATION(SOToleranceViolation);

    //_ASSERTE(nul == 0);
    m_asObj = (Object*)nul;
    if( m_asObj != NULL)
    {
        // REVISIT_TODO: fix this, why is this constructor being used for non-null object refs?
        STATIC_CONTRACT_VIOLATION(ModeViolation);

        VALIDATEOBJECT(m_asObj);
        ENABLESTRESSHEAP();
    }
    Thread::ObjectRefNew(this);
}

//-------------------------------------------------------------
// This is for the GC's use only. Non-GC code should never
// use the "Object" class directly. The unused "int" argument
// prevents C++ from using this to implicitly convert Object*'s
// to OBJECTREF.
//-------------------------------------------------------------
OBJECTREF::OBJECTREF(Object *pObject)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_MODE_COOPERATIVE;
    STATIC_CONTRACT_FORBID_FAULT;

    DEBUG_ONLY_FUNCTION;
    
    if ((pObject != 0) &&
        ((GCHeap*)GCHeap::GetGCHeap())->IsHeapPointer( (BYTE*)this ))
    {
        _ASSERTE(!"Write Barrier violation. Must use SetObjectReference() to assign OBJECTREF's into the GC heap!");
    }
    m_asObj = pObject;
    VALIDATEOBJECT(m_asObj);
    if (m_asObj != 0) {
        ENABLESTRESSHEAP();
    }
    Thread::ObjectRefNew(this);
}

void OBJECTREF::Validate(BOOL bDeep, BOOL bVerifyNextHeader, BOOL bVerifySyncBlock)
{
    LIMITED_METHOD_CONTRACT;
    m_asObj->Validate(bDeep, bVerifyNextHeader, bVerifySyncBlock);
}

//-------------------------------------------------------------
// Test against NULL.
//-------------------------------------------------------------
int OBJECTREF::operator!() const
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

    // We don't do any validation here, as we want to allow zero comparison in preemptive mode
    return !m_asObj;
}

//-------------------------------------------------------------
// Compare two OBJECTREF's.
//-------------------------------------------------------------
int OBJECTREF::operator==(const OBJECTREF &objref) const
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

    if (objref.m_asObj != NULL) // Allow comparison to zero in preemptive mode
    {
        // REVISIT_TODO: Weakening the contract system a little bit here. We should really
        // add a special NULLOBJECTREF which can be used for these situations and have
        // a seperate code path for that with the correct contract protections.
        STATIC_CONTRACT_VIOLATION(ModeViolation);

        VALIDATEOBJECT(objref.m_asObj);

        // !!! If this assert is fired, there are two possibilities:
        // !!! 1.  You are doing a type cast, e.g.  *(OBJECTREF*)pObj
        // !!!     Instead, you should use ObjectToOBJECTREF(*(Object**)pObj),
        // !!!                          or ObjectToSTRINGREF(*(StringObject**)pObj)
        // !!! 2.  There is a real GC hole here.
        // !!! Either way you need to fix the code.
        _ASSERTE(Thread::IsObjRefValid(&objref));
        VALIDATEOBJECT(m_asObj);
        // If this assert fires, you probably did not protect
        // your OBJECTREF and a GC might have occurred.  To
        // where the possible GC was, set a breakpoint in Thread::TriggersGC 
        _ASSERTE(Thread::IsObjRefValid(this));

        if (m_asObj != 0 || objref.m_asObj != 0) {
            ENABLESTRESSHEAP();
        }
    }
    return m_asObj == objref.m_asObj;
}

//-------------------------------------------------------------
// Compare two OBJECTREF's.
//-------------------------------------------------------------
int OBJECTREF::operator!=(const OBJECTREF &objref) const
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

    if (objref.m_asObj != NULL)  // Allow comparison to zero in preemptive mode
    {
        // REVISIT_TODO: Weakening the contract system a little bit here. We should really
        // add a special NULLOBJECTREF which can be used for these situations and have
        // a seperate code path for that with the correct contract protections.
        STATIC_CONTRACT_VIOLATION(ModeViolation);

        VALIDATEOBJECT(objref.m_asObj);

        // !!! If this assert is fired, there are two possibilities:
        // !!! 1.  You are doing a type cast, e.g.  *(OBJECTREF*)pObj
        // !!!     Instead, you should use ObjectToOBJECTREF(*(Object**)pObj),
        // !!!                          or ObjectToSTRINGREF(*(StringObject**)pObj)
        // !!! 2.  There is a real GC hole here.
        // !!! Either way you need to fix the code.
        _ASSERTE(Thread::IsObjRefValid(&objref));
        VALIDATEOBJECT(m_asObj);
        // If this assert fires, you probably did not protect
        // your OBJECTREF and a GC might have occurred.  To
        // where the possible GC was, set a breakpoint in Thread::TriggersGC 
        _ASSERTE(Thread::IsObjRefValid(this));

        if (m_asObj != 0 || objref.m_asObj != 0) {
            ENABLESTRESSHEAP();
        }
    }

    return m_asObj != objref.m_asObj;
}


//-------------------------------------------------------------
// Forward method calls.
//-------------------------------------------------------------
Object* OBJECTREF::operator->()
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

    VALIDATEOBJECT(m_asObj);
        // If this assert fires, you probably did not protect
        // your OBJECTREF and a GC might have occurred.  To
        // where the possible GC was, set a breakpoint in Thread::TriggersGC 
    _ASSERTE(Thread::IsObjRefValid(this));

    if (m_asObj != 0) {
        ENABLESTRESSHEAP();
    }

    // if you are using OBJECTREF directly,
    // you probably want an Object *
    return (Object *)m_asObj;
}


//-------------------------------------------------------------
// Forward method calls.
//-------------------------------------------------------------
const Object* OBJECTREF::operator->() const
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

    VALIDATEOBJECT(m_asObj);
        // If this assert fires, you probably did not protect
        // your OBJECTREF and a GC might have occurred.  To
        // where the possible GC was, set a breakpoint in Thread::TriggersGC 
    _ASSERTE(Thread::IsObjRefValid(this));

    if (m_asObj != 0) {
        ENABLESTRESSHEAP();
    }

    // if you are using OBJECTREF directly,
    // you probably want an Object *
    return (Object *)m_asObj;
}


//-------------------------------------------------------------
// Assignment. We don't validate the destination so as not
// to break the sequence:
//
//      OBJECTREF or;
//      or = ...;
//-------------------------------------------------------------
OBJECTREF& OBJECTREF::operator=(const OBJECTREF &objref)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

    VALIDATEOBJECT(objref.m_asObj);

    // !!! If this assert is fired, there are two possibilities:
    // !!! 1.  You are doing a type cast, e.g.  *(OBJECTREF*)pObj
    // !!!     Instead, you should use ObjectToOBJECTREF(*(Object**)pObj),
    // !!!                          or ObjectToSTRINGREF(*(StringObject**)pObj)
    // !!! 2.  There is a real GC hole here.
    // !!! Either way you need to fix the code.
    _ASSERTE(Thread::IsObjRefValid(&objref));

    if ((objref.m_asObj != 0) &&
        ((GCHeap*)GCHeap::GetGCHeap())->IsHeapPointer( (BYTE*)this ))
    {
        _ASSERTE(!"Write Barrier violation. Must use SetObjectReference() to assign OBJECTREF's into the GC heap!");
    }
    Thread::ObjectRefAssign(this);

    m_asObj = objref.m_asObj;
    if (m_asObj != 0) {
        ENABLESTRESSHEAP();
    }
    return *this;
}

//-------------------------------------------------------------
// Allows for the assignment of NULL to a OBJECTREF 
//-------------------------------------------------------------

OBJECTREF& OBJECTREF::operator=(TADDR nul)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;

    _ASSERTE(nul == 0);
    Thread::ObjectRefAssign(this);
    m_asObj = (Object*)nul;
    if (m_asObj != 0) {
        ENABLESTRESSHEAP();
    }
    return *this;
}
#endif  // DEBUG

#ifdef _DEBUG

void* __cdecl GCSafeMemCpy(void * dest, const void * src, size_t len)
{
    STATIC_CONTRACT_NOTHROW;
    STATIC_CONTRACT_GC_NOTRIGGER;
    STATIC_CONTRACT_FORBID_FAULT;
    STATIC_CONTRACT_SO_TOLERANT;

    if (!(((*(BYTE**)&dest) <  g_lowest_address ) ||
          ((*(BYTE**)&dest) >= g_highest_address)))
    {
        Thread* pThread = GetThread();

        // GCHeap::IsHeapPointer has race when called in preemptive mode. It walks the list of segments
        // that can be modified by GC. Do the check below only if it is safe to do so.
        if (pThread != NULL && pThread->PreemptiveGCDisabled())
        {
            // Note there is memcpyNoGCRefs which will allow you to do a memcpy into the GC
            // heap if you really know you don't need to call the write barrier

            _ASSERTE(!GCHeap::GetGCHeap()->IsHeapPointer((BYTE *) dest) ||
                     !"using memcpy to copy into the GC heap, use CopyValueClass");
        }
    }
    return memcpyNoGCRefs(dest, src, len);
}

#endif // _DEBUG

// This function clears a piece of memory in a GC safe way.  It makes the guarantee
// that it will clear memory in at least pointer sized chunks whenever possible.
// Unaligned memory at the beginning and remaining bytes at the end are written bytewise.
// We must make this guarantee whenever we clear memory in the GC heap that could contain 
// object references.  The GC or other user threads can read object references at any time, 
// clearing them bytewise can result in a read on another thread getting incorrect data.  
void __fastcall ZeroMemoryInGCHeap(void* mem, size_t size)
{
    WRAPPER_NO_CONTRACT;
    BYTE* memBytes = (BYTE*) mem;
    BYTE* endBytes = &memBytes[size];

    // handle unaligned bytes at the beginning
    while (!IS_ALIGNED(memBytes, sizeof(PTR_PTR_VOID)) && memBytes < endBytes)
        *memBytes++ = 0;

    // now write pointer sized pieces
    size_t nPtrs = (endBytes - memBytes) / sizeof(PTR_PTR_VOID);
    PTR_PTR_VOID memPtr = (PTR_PTR_VOID) memBytes;
    for (size_t i = 0; i < nPtrs; i++)
        *memPtr++ = 0;

    // handle remaining bytes at the end
    memBytes = (BYTE*) memPtr;
    while (memBytes < endBytes)
        *memBytes++ = 0;
}

void StackTraceArray::Append(StackTraceElement const * begin, StackTraceElement const * end)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
    }
    CONTRACTL_END;

    // ensure that only one thread can write to the array
    EnsureThreadAffinity();

    size_t newsize = Size() + (end - begin);
    Grow(newsize);
    memcpyNoGCRefs(GetData() + Size(), begin, (end - begin) * sizeof(StackTraceElement));
    MemoryBarrier();  // prevent the newsize from being reordered with the array copy
    SetSize(newsize);

#if defined(_DEBUG)
    CheckState();
#endif
}

void StackTraceArray::AppendSkipLast(StackTraceElement const * begin, StackTraceElement const * end)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
    }
    CONTRACTL_END;

    // to skip the last element, we need to replace it with the first element
    // from m_pStackTrace and do it atomically if possible,
    // otherwise we'll create a copy of the entire array, which is bad for performance,
    // and so should not be on the main path
    //

    // ensure that only one thread can write to the array
    EnsureThreadAffinity();

    assert(Size() > 0);

    StackTraceElement & last = GetData()[Size() - 1];
    if (last.PartiallyEqual(*begin))
    {
        // fast path: atomic update
        last.PartialAtomicUpdate(*begin);

        // append the rest
        if (end - begin > 1)
            Append(begin + 1, end);
    }
    else
    {
        // slow path: create a copy and append
        StackTraceArray copy(*this);
        GCPROTECT_BEGIN(copy);
            copy.SetSize(copy.Size() - 1);
            copy.Append(begin, end);
            this->Swap(copy);
        GCPROTECT_END();
    }

#if defined(_DEBUG)
    CheckState();
#endif
}

void StackTraceArray::CheckState() const
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        MODE_COOPERATIVE;
    }
    CONTRACTL_END;
    
    if (!m_array)
        return;

    assert(GetObjectThread() == GetThread());
    
    size_t size = Size();
    StackTraceElement const * p;
    p = GetData();
    for (size_t i = 0; i < size; ++i)
        assert(p[i].pFunc != NULL);
}

void StackTraceArray::Grow(size_t grow_size)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        INJECT_FAULT(ThrowOutOfMemory(););
    }
    CONTRACTL_END;

    size_t raw_size = grow_size * sizeof(StackTraceElement) + sizeof(ArrayHeader);

    if (!m_array)
    {
        SetArray(I1ARRAYREF(AllocatePrimitiveArray(ELEMENT_TYPE_I1, static_cast<DWORD>(raw_size))));
        SetSize(0);
        SetObjectThread();
    }
    else
    {
        if (Capacity() >= raw_size)
            return;

        // allocate a new array, copy the data
        size_t new_capacity = Max(Capacity() * 2, raw_size);

        _ASSERTE(new_capacity >= grow_size * sizeof(StackTraceElement) + sizeof(ArrayHeader));
        
        I1ARRAYREF newarr = (I1ARRAYREF) AllocatePrimitiveArray(ELEMENT_TYPE_I1, static_cast<DWORD>(new_capacity));
        memcpyNoGCRefs(newarr->GetDirectPointerToNonObjectElements(),
                       GetRaw(),
                       Size() * sizeof(StackTraceElement) + sizeof(ArrayHeader));

        SetArray(newarr);
    }
}

void StackTraceArray::EnsureThreadAffinity()
{
    WRAPPER_NO_CONTRACT;

    if (!m_array)
        return;

    if (GetObjectThread() != GetThread())
    {
        // object is being changed by a thread different from the one which created it
        // make a copy of the array to prevent a race condition when two different threads try to change it
        StackTraceArray copy(*this);
        this->Swap(copy);
    }
}

#ifdef _MSC_VER
#pragma warning(disable: 4267) 
#endif

StackTraceArray::StackTraceArray(StackTraceArray const & rhs)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        INJECT_FAULT(ThrowOutOfMemory(););
    }
    CONTRACTL_END;

    m_array = (I1ARRAYREF) AllocatePrimitiveArray(ELEMENT_TYPE_I1, static_cast<DWORD>(rhs.Capacity()));

    GCPROTECT_BEGIN(m_array);
        Volatile<size_t> size = rhs.Size();
        memcpyNoGCRefs(GetRaw(), rhs.GetRaw(), size * sizeof(StackTraceElement) + sizeof(ArrayHeader));

        SetSize(size);  // set size to the exact value which was used when we copied the data
                        // another thread might have changed it at the time of copying
        SetObjectThread();  // affinitize the newly created array with the current thread
    GCPROTECT_END();
}

// Deep copies the stack trace array
void StackTraceArray::CopyFrom(StackTraceArray const & src)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        INJECT_FAULT(ThrowOutOfMemory(););
    }
    CONTRACTL_END;

    m_array = (I1ARRAYREF) AllocatePrimitiveArray(ELEMENT_TYPE_I1, static_cast<DWORD>(src.Capacity()));

    GCPROTECT_BEGIN(m_array);
    Volatile<size_t> size = src.Size();
    memcpyNoGCRefs(GetRaw(), src.GetRaw(), size * sizeof(StackTraceElement) + sizeof(ArrayHeader));

    SetSize(size);  // set size to the exact value which was used when we copied the data
                    // another thread might have changed it at the time of copying
    SetObjectThread();  // affinitize the newly created array with the current thread
    GCPROTECT_END();
}

#ifdef _MSC_VER
#pragma warning(default: 4267)
#endif


#ifdef _DEBUG
//===============================================================================
// Code that insures that our unmanaged version of Nullable is consistant with
// the managed version Nullable<T> for all T.  

void Nullable::CheckFieldOffsets(TypeHandle nullableType) 
{
    LIMITED_METHOD_CONTRACT;

/***
        // The non-instantiated method tables like List<T> that are used
        // by reflection and verification do not have correct field offsets
        // but we never make instances of these anyway.
    if (nullableMT->ContainsGenericVariables())
        return;
***/

    MethodTable* nullableMT = nullableType.GetMethodTable();

        // insure that the managed version of the table is the same as the
        // unmanaged.  Note that we can't do this in mscorlib.h because this
        // class is generic and field layout depends on the instantiation.

    _ASSERTE(nullableMT->GetNumInstanceFields() == 2);
    FieldDesc* field = nullableMT->GetApproxFieldDescListRaw();

    _ASSERTE(strcmp(field->GetDebugName(), "hasValue") == 0);
//     _ASSERTE(field->GetOffset() == offsetof(Nullable, hasValue));
    field++;

    _ASSERTE(strcmp(field->GetDebugName(), "value") == 0);
//     _ASSERTE(field->GetOffset() == offsetof(Nullable, value));
}
#endif

//===============================================================================
// Returns true if nullableMT is Nullable<T> for T is equivalent to paramMT

BOOL Nullable::IsNullableForTypeHelper(MethodTable* nullableMT, MethodTable* paramMT)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        SO_TOLERANT;
        MODE_ANY;
    }
    CONTRACTL_END;
    if (!nullableMT->IsNullable())
        return FALSE;

    // we require the parameter types to be equivalent
    return TypeHandle(paramMT).IsEquivalentTo(nullableMT->GetInstantiation()[0]);
}

//===============================================================================
// Returns true if nullableMT is Nullable<T> for T == paramMT

BOOL Nullable::IsNullableForTypeHelperNoGC(MethodTable* nullableMT, MethodTable* paramMT)
{
    LIMITED_METHOD_CONTRACT;
    if (!nullableMT->IsNullable())
        return FALSE;

    // we require an exact match of the parameter types 
    return TypeHandle(paramMT) == nullableMT->GetInstantiation()[0];
}
    
//===============================================================================
CLR_BOOL* Nullable::HasValueAddr(MethodTable* nullableMT) {

    LIMITED_METHOD_CONTRACT;

    _ASSERTE(strcmp(nullableMT->GetApproxFieldDescListRaw()[0].GetDebugName(), "hasValue") == 0);
    _ASSERTE(nullableMT->GetApproxFieldDescListRaw()[0].GetOffset() == 0);
    return (CLR_BOOL*) this;
}

//===============================================================================
void* Nullable::ValueAddr(MethodTable* nullableMT) {

    LIMITED_METHOD_CONTRACT;

    _ASSERTE(strcmp(nullableMT->GetApproxFieldDescListRaw()[1].GetDebugName(), "value") == 0);
    return (((BYTE*) this) + nullableMT->GetApproxFieldDescListRaw()[1].GetOffset());
}

//===============================================================================
// Special Logic to box a nullable<T> as a boxed<T>

OBJECTREF Nullable::Box(void* srcPtr, MethodTable* nullableMT)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
    }
    CONTRACTL_END;

    FAULT_NOT_FATAL();      // FIX_NOW: why do we need this?

    Nullable* src = (Nullable*) srcPtr;

    _ASSERTE(IsNullableType(nullableMT));
        // We better have a concrete instantiation, or our field offset asserts are not useful
    _ASSERTE(!nullableMT->ContainsGenericVariables());

    if (!*src->HasValueAddr(nullableMT))
        return NULL;

    OBJECTREF obj = 0;
    GCPROTECT_BEGININTERIOR (src);
    MethodTable* argMT = nullableMT->GetInstantiation()[0].GetMethodTable();
    obj = argMT->Allocate();
    CopyValueClass(obj->UnBox(), src->ValueAddr(nullableMT), argMT, obj->GetAppDomain());
    GCPROTECT_END ();

    return obj;
}

//===============================================================================
// Special Logic to unbox a boxed T as a nullable<T>

BOOL Nullable::UnBox(void* destPtr, OBJECTREF boxedVal, MethodTable* destMT)
{
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
        SO_TOLERANT;
    }
    CONTRACTL_END;
    Nullable* dest = (Nullable*) destPtr;
    BOOL fRet = TRUE;

        // We should only get here if we are unboxing a T as a Nullable<T>
    _ASSERTE(IsNullableType(destMT));

        // We better have a concrete instantiation, or our field offset asserts are not useful
    _ASSERTE(!destMT->ContainsGenericVariables());

    if (boxedVal == NULL) 
    {
        // Logically we are doing *dest->HasValueAddr(destMT) = false;
        // We zero out the whole structure becasue it may contain GC references
        // and these need to be initialized to zero.   (could optimize in the non-GC case)
        InitValueClass(destPtr, destMT);
        fRet = TRUE;
    }
    else 
    {
        GCPROTECT_BEGIN(boxedVal);
        if (!IsNullableForType(destMT, boxedVal->GetMethodTable()))
        {
            // For safety's sake, also allow true nullables to be unboxed normally.  
            // This should not happen normally, but we want to be robust
            if (destMT->IsEquivalentTo(boxedVal->GetMethodTable()))
            {
                CopyValueClass(dest, boxedVal->GetData(), destMT, boxedVal->GetAppDomain());
                fRet = TRUE;
            }
            else
            {
                fRet = FALSE;
            }
        }
        else
        {
            *dest->HasValueAddr(destMT) = true;
            CopyValueClass(dest->ValueAddr(destMT), boxedVal->UnBox(), boxedVal->GetMethodTable(), boxedVal->GetAppDomain());
            fRet = TRUE;
        }
        GCPROTECT_END();
    }
    return fRet;
}

//===============================================================================
// Special Logic to unbox a boxed T as a nullable<T>
// Does not handle type equivalence (may conservatively return FALSE)
BOOL Nullable::UnBoxNoGC(void* destPtr, OBJECTREF boxedVal, MethodTable* destMT)
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        MODE_COOPERATIVE;
        SO_TOLERANT;
    }
    CONTRACTL_END;
    Nullable* dest = (Nullable*) destPtr;

        // We should only get here if we are unboxing a T as a Nullable<T>
    _ASSERTE(IsNullableType(destMT));

        // We better have a concrete instantiation, or our field offset asserts are not useful
    _ASSERTE(!destMT->ContainsGenericVariables());

    if (boxedVal == NULL) 
    {
        // Logically we are doing *dest->HasValueAddr(destMT) = false;
        // We zero out the whole structure becasue it may contain GC references
        // and these need to be initialized to zero.   (could optimize in the non-GC case)
        InitValueClass(destPtr, destMT);
    }
    else 
    {
        if (!IsNullableForTypeNoGC(destMT, boxedVal->GetMethodTable()))
        {
            // For safety's sake, also allow true nullables to be unboxed normally.  
            // This should not happen normally, but we want to be robust
            if (destMT == boxedVal->GetMethodTable())
            {
                CopyValueClass(dest, boxedVal->GetData(), destMT, boxedVal->GetAppDomain());
                return TRUE;
            }
            return FALSE;
        }

        *dest->HasValueAddr(destMT) = true;
        CopyValueClass(dest->ValueAddr(destMT), boxedVal->UnBox(), boxedVal->GetMethodTable(), boxedVal->GetAppDomain());
    }
    return TRUE;
}

//===============================================================================
// Special Logic to unbox a boxed T as a nullable<T> into an argument 
// specified by the argDest.
// Does not handle type equivalence (may conservatively return FALSE)
BOOL Nullable::UnBoxIntoArgNoGC(ArgDestination *argDest, OBJECTREF boxedVal, MethodTable* destMT)
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        MODE_COOPERATIVE;
        SO_TOLERANT;
    }
    CONTRACTL_END;

#if defined(UNIX_AMD64_ABI) && defined(FEATURE_UNIX_AMD64_STRUCT_PASSING)
    if (argDest->IsStructPassedInRegs())
    {
        // We should only get here if we are unboxing a T as a Nullable<T>
        _ASSERTE(IsNullableType(destMT));

        // We better have a concrete instantiation, or our field offset asserts are not useful
        _ASSERTE(!destMT->ContainsGenericVariables());

        if (boxedVal == NULL) 
        {
            // Logically we are doing *dest->HasValueAddr(destMT) = false;
            // We zero out the whole structure becasue it may contain GC references
            // and these need to be initialized to zero.   (could optimize in the non-GC case)
            InitValueClassArg(argDest, destMT);
        }
        else 
        {
            if (!IsNullableForTypeNoGC(destMT, boxedVal->GetMethodTable()))
            {
                // For safety's sake, also allow true nullables to be unboxed normally.  
                // This should not happen normally, but we want to be robust
                if (destMT == boxedVal->GetMethodTable())
                {
                    CopyValueClassArg(argDest, boxedVal->GetData(), destMT, boxedVal->GetAppDomain(), 0);
                    return TRUE;
                }
                return FALSE;
            }

            Nullable* dest = (Nullable*)argDest->GetStructGenRegDestinationAddress();
            *dest->HasValueAddr(destMT) = true;
            int destOffset = (BYTE*)dest->ValueAddr(destMT) - (BYTE*)dest;
            CopyValueClassArg(argDest, boxedVal->UnBox(), boxedVal->GetMethodTable(), boxedVal->GetAppDomain(), destOffset);
        }
        return TRUE;
    }

#endif // UNIX_AMD64_ABI && FEATURE_UNIX_AMD64_STRUCT_PASSING

    return UnBoxNoGC(argDest->GetDestinationAddress(), boxedVal, destMT);
}

//===============================================================================
// Special Logic to unbox a boxed T as a nullable<T>
// Does not do any type checks.
void Nullable::UnBoxNoCheck(void* destPtr, OBJECTREF boxedVal, MethodTable* destMT)
{
    CONTRACTL
    {
        NOTHROW;
        GC_NOTRIGGER;
        MODE_COOPERATIVE;
        SO_TOLERANT;
    }
    CONTRACTL_END;
    Nullable* dest = (Nullable*) destPtr;

        // We should only get here if we are unboxing a T as a Nullable<T>
    _ASSERTE(IsNullableType(destMT));

        // We better have a concrete instantiation, or our field offset asserts are not useful
    _ASSERTE(!destMT->ContainsGenericVariables());

    if (boxedVal == NULL) 
    {
        // Logically we are doing *dest->HasValueAddr(destMT) = false;
        // We zero out the whole structure becasue it may contain GC references
        // and these need to be initialized to zero.   (could optimize in the non-GC case)
        InitValueClass(destPtr, destMT);
    }
    else 
    {
        if (IsNullableType(boxedVal->GetMethodTable()))
        {
            // For safety's sake, also allow true nullables to be unboxed normally.  
            // This should not happen normally, but we want to be robust
            CopyValueClass(dest, boxedVal->GetData(), destMT, boxedVal->GetAppDomain());
        }

        *dest->HasValueAddr(destMT) = true;
        CopyValueClass(dest->ValueAddr(destMT), boxedVal->UnBox(), boxedVal->GetMethodTable(), boxedVal->GetAppDomain());
    }
}

//===============================================================================
// a boxed Nullable<T> should either be null or a boxed T, but sometimes it is
// useful to have a 'true' boxed Nullable<T> (that is it has two fields).  This
// function returns a 'normalized' version of this pointer.

OBJECTREF Nullable::NormalizeBox(OBJECTREF obj) {
    CONTRACTL
    {
        THROWS;
        GC_TRIGGERS;
        MODE_COOPERATIVE;
    }
    CONTRACTL_END;

    if (obj != NULL) {
        MethodTable* retMT = obj->GetMethodTable();
        if (Nullable::IsNullableType(retMT)) 
            obj = Nullable::Box(obj->GetData(), retMT);
    }
    return obj;
}


void ThreadBaseObject::SetInternal(Thread *it)
{
    WRAPPER_NO_CONTRACT;

    // only allow a transition from NULL to non-NULL
    _ASSERTE((m_InternalThread == NULL) && (it != NULL));
    m_InternalThread = it;

    // Now the native Thread will only be destroyed after the managed Thread is collected.
    // Tell the GC that the managed Thread actually represents much more memory.
    GCInterface::NewAddMemoryPressure(sizeof(Thread));
}

void ThreadBaseObject::ClearInternal()
{
    WRAPPER_NO_CONTRACT;

    _ASSERTE(m_InternalThread != NULL);
    m_InternalThread = NULL;
    GCInterface::NewRemoveMemoryPressure(sizeof(Thread));
}

#endif // #ifndef DACCESS_COMPILE


StackTraceElement const & StackTraceArray::operator[](size_t index) const
{
    WRAPPER_NO_CONTRACT;
    return GetData()[index];
}

StackTraceElement & StackTraceArray::operator[](size_t index)
{
    WRAPPER_NO_CONTRACT;
    return GetData()[index];
}

#if !defined(DACCESS_COMPILE)
// Define the lock used to access stacktrace from an exception object
SpinLock g_StackTraceArrayLock;

void ExceptionObject::SetStackTrace(StackTraceArray const & stackTrace, PTRARRAYREF dynamicMethodArray)
{        
    CONTRACTL
    {
        GC_NOTRIGGER;
        NOTHROW;
        MODE_COOPERATIVE;
        SO_TOLERANT;
    }
    CONTRACTL_END;

    Thread *m_pThread = GetThread();
    SpinLock::AcquireLock(&g_StackTraceArrayLock, SPINLOCK_THREAD_PARAM_ONLY_IN_SOME_BUILDS);

    SetObjectReference((OBJECTREF*)&_stackTrace, (OBJECTREF)stackTrace.Get(), GetAppDomain());
    SetObjectReference((OBJECTREF*)&_dynamicMethods, (OBJECTREF)dynamicMethodArray, GetAppDomain());

    SpinLock::ReleaseLock(&g_StackTraceArrayLock, SPINLOCK_THREAD_PARAM_ONLY_IN_SOME_BUILDS);

}

void ExceptionObject::SetNullStackTrace()
{        
    CONTRACTL
    {
        GC_NOTRIGGER;
        NOTHROW;
        MODE_COOPERATIVE;
        SO_TOLERANT;
    }
    CONTRACTL_END;

    Thread *m_pThread = GetThread();
    SpinLock::AcquireLock(&g_StackTraceArrayLock, SPINLOCK_THREAD_PARAM_ONLY_IN_SOME_BUILDS);

    I1ARRAYREF stackTraceArray = NULL;
    PTRARRAYREF dynamicMethodArray = NULL;

    SetObjectReference((OBJECTREF*)&_stackTrace, (OBJECTREF)stackTraceArray, GetAppDomain());
    SetObjectReference((OBJECTREF*)&_dynamicMethods, (OBJECTREF)dynamicMethodArray, GetAppDomain());

    SpinLock::ReleaseLock(&g_StackTraceArrayLock, SPINLOCK_THREAD_PARAM_ONLY_IN_SOME_BUILDS);
}

#endif // !defined(DACCESS_COMPILE)

void ExceptionObject::GetStackTrace(StackTraceArray & stackTrace, PTRARRAYREF * outDynamicMethodArray /*= NULL*/) const
{
    CONTRACTL
    {
        GC_NOTRIGGER;
        NOTHROW;
        MODE_COOPERATIVE;
        SO_TOLERANT;
    }
    CONTRACTL_END;

#if !defined(DACCESS_COMPILE)
    Thread *m_pThread = GetThread();
    SpinLock::AcquireLock(&g_StackTraceArrayLock, SPINLOCK_THREAD_PARAM_ONLY_IN_SOME_BUILDS);
#endif // !defined(DACCESS_COMPILE)

    StackTraceArray temp(_stackTrace);
    stackTrace.Swap(temp);

    if (outDynamicMethodArray != NULL)
    {
        *outDynamicMethodArray = _dynamicMethods;
    }

#if !defined(DACCESS_COMPILE)
    SpinLock::ReleaseLock(&g_StackTraceArrayLock, SPINLOCK_THREAD_PARAM_ONLY_IN_SOME_BUILDS);
#endif // !defined(DACCESS_COMPILE)

}