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BENCH: Remove ExInfo::m_hThrowable — exception handling benchmarks #127531

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BENCH: Remove ExInfo::m_hThrowable — exception handling benchmarks #127531

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7aae554
Remove ExInfo::m_hThrowable — use direct pointer for exception objects
max-charlamb Apr 21, 2026
b032961
Fix GC hole: remove double-reporting of ExInfo::m_exception
max-charlamb Apr 24, 2026
1192b46
Update SafeSetThrowables comment to reflect current behavior
max-charlamb Apr 28, 2026
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24 changes: 12 additions & 12 deletions src/coreclr/System.Private.CoreLib/src/System/Runtime/ExceptionServices/AsmOffsets.cs
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Expand Up @@ -189,12 +189,12 @@ class AsmOffsets
public const int SIZEOF__EHEnum = 0x20;
public const int OFFSETOF__StackFrameIterator__m_pRegDisplay = 0x20;
public const int OFFSETOF__ExInfo__m_pPrevExInfo = 0;
public const int OFFSETOF__ExInfo__m_pExContext = 0xa8;
public const int OFFSETOF__ExInfo__m_exception = 0xb0;
public const int OFFSETOF__ExInfo__m_kind = 0xb8;
public const int OFFSETOF__ExInfo__m_passNumber = 0xb9;
public const int OFFSETOF__ExInfo__m_idxCurClause = 0xbc;
public const int OFFSETOF__ExInfo__m_frameIter = 0xc0;
public const int OFFSETOF__ExInfo__m_pExContext = 0xa0;
public const int OFFSETOF__ExInfo__m_exception = 0xa8;
public const int OFFSETOF__ExInfo__m_kind = 0xb0;
public const int OFFSETOF__ExInfo__m_passNumber = 0xb1;
public const int OFFSETOF__ExInfo__m_idxCurClause = 0xb4;
public const int OFFSETOF__ExInfo__m_frameIter = 0xb8;
public const int OFFSETOF__ExInfo__m_notifyDebuggerSP = OFFSETOF__ExInfo__m_frameIter + SIZEOF__StackFrameIterator;
public const int OFFSETOF__ExInfo__m_pCatchHandler = OFFSETOF__ExInfo__m_frameIter + SIZEOF__StackFrameIterator + 0x48;
public const int OFFSETOF__ExInfo__m_handlingFrameSP = OFFSETOF__ExInfo__m_frameIter + SIZEOF__StackFrameIterator + 0x50;
Expand All @@ -217,12 +217,12 @@ class AsmOffsets
public const int SIZEOF__EHEnum = 0x10;
public const int OFFSETOF__StackFrameIterator__m_pRegDisplay = 0x14;
public const int OFFSETOF__ExInfo__m_pPrevExInfo = 0;
public const int OFFSETOF__ExInfo__m_pExContext = 0x5c;
public const int OFFSETOF__ExInfo__m_exception = 0x60;
public const int OFFSETOF__ExInfo__m_kind = 0x64;
public const int OFFSETOF__ExInfo__m_passNumber = 0x65;
public const int OFFSETOF__ExInfo__m_idxCurClause = 0x68;
public const int OFFSETOF__ExInfo__m_frameIter = 0x6c;
public const int OFFSETOF__ExInfo__m_pExContext = 0x58;
public const int OFFSETOF__ExInfo__m_exception = 0x5c;
public const int OFFSETOF__ExInfo__m_kind = 0x60;
public const int OFFSETOF__ExInfo__m_passNumber = 0x61;
public const int OFFSETOF__ExInfo__m_idxCurClause = 0x64;
public const int OFFSETOF__ExInfo__m_frameIter = 0x68;
public const int OFFSETOF__ExInfo__m_notifyDebuggerSP = OFFSETOF__ExInfo__m_frameIter + SIZEOF__StackFrameIterator;
public const int OFFSETOF__ExInfo__m_pCatchHandler = OFFSETOF__ExInfo__m_frameIter + SIZEOF__StackFrameIterator + 0x2c;
public const int OFFSETOF__ExInfo__m_handlingFrameSP = OFFSETOF__ExInfo__m_frameIter + SIZEOF__StackFrameIterator + 0x30;
Expand Down
12 changes: 7 additions & 5 deletions src/coreclr/debug/daccess/dacdbiimpl.cpp
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Expand Up @@ -4817,9 +4817,9 @@ HRESULT STDMETHODCALLTYPE DacDbiInterfaceImpl::HasUnhandledException(VMPTR_Threa
else
{
// most managed exceptions are just a throwable bound to a
// native exception. In that case this handle will be non-null
OBJECTHANDLE ohException = pThread->GetThrowableAsHandle();
if (ohException != (OBJECTHANDLE)NULL)
// native exception. In that case the exception will be non-null
OBJECTREF exception = pThread->GetExceptionState()->GetThrowable();
if (exception != NULL)
{
// during the UEF we set the unhandled bit, if it is set the exception
// was unhandled
Expand Down Expand Up @@ -4955,8 +4955,10 @@ HRESULT STDMETHODCALLTYPE DacDbiInterfaceImpl::GetCurrentException(VMPTR_Thread

Thread * pThread = vmThread.GetDacPtr();

// OBJECTHANDLEs are really just TADDRs.
OBJECTHANDLE ohException = pThread->GetThrowableAsHandle(); // ohException can be NULL
// Get the exception handle. The exception object is stored directly in ExInfo::m_exception,
// but debugger APIs require a handle. Use m_LastThrownObjectHandle which is kept in sync
// via SafeSetThrowables.
OBJECTHANDLE ohException = pThread->m_LastThrownObjectHandle;

if (ohException == (OBJECTHANDLE)NULL)
{
Expand Down
7 changes: 7 additions & 0 deletions src/coreclr/debug/daccess/dacimpl.h
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Expand Up @@ -3397,6 +3397,13 @@ class ClrDataExceptionState : public IXCLRDataExceptionState
Thread* thread,
ULONG32 flags,
ClrDataExStateType* exInfo,
// Target address of a slot containing the exception Object*.
// This may be a GC handle table slot (e.g. m_LastThrownObjectHandle)
// or the address of ExInfo::m_exception on the target stack.
// Both are valid: the ExInfo lives on the stack which is captured
// in dumps and stable while the target thread is suspended. The
// slot has the same lifetime as the ExInfo — both become invalid
// when ExInfo::PopExInfos calls ReleaseResources.
OBJECTHANDLE throwable,
ClrDataExStateType* prevExInfo);
virtual ~ClrDataExceptionState(void);
Expand Down
47 changes: 21 additions & 26 deletions src/coreclr/debug/daccess/request.cpp
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Expand Up @@ -3308,7 +3308,7 @@ ClrDataAccess::GetNestedExceptionData(CLRDATA_ADDRESS exception, CLRDATA_ADDRESS
}
else
{
*exceptionObject = TO_CDADDR(*PTR_TADDR(pExData->m_hThrowable));
*exceptionObject = dac_cast<TADDR>(pExData->m_exception);
*nextNestedException = PTR_HOST_TO_TADDR(pExData->m_pPrevNestedInfo);
}

Expand Down Expand Up @@ -4064,35 +4064,30 @@ HRESULT ClrDataAccess::GetClrWatsonBucketsWorker(Thread * pThread, GenericModeBl
// By default, there are no buckets
PTR_VOID pBuckets = NULL;

// Get the handle to the throwble
OBJECTHANDLE ohThrowable = pThread->GetThrowableAsHandle();
if (ohThrowable != NULL)
// Get the current throwable
OBJECTREF oThrowable = pThread->GetExceptionState()->GetThrowable();
if (oThrowable != NULL)
{
// Get the object from handle and check if the throwable is preallocated or not
OBJECTREF oThrowable = ObjectFromHandle(ohThrowable);
if (oThrowable != NULL)
// Does the throwable have buckets?
U1ARRAYREF refWatsonBucketArray = ((EXCEPTIONREF)oThrowable)->GetWatsonBucketReference();
if (refWatsonBucketArray != NULL)
{
// Does the throwable have buckets?
U1ARRAYREF refWatsonBucketArray = ((EXCEPTIONREF)oThrowable)->GetWatsonBucketReference();
if (refWatsonBucketArray != NULL)
{
// Get the watson buckets from the throwable for non-preallocated
// exceptions
pBuckets = dac_cast<PTR_VOID>(refWatsonBucketArray->GetDataPtr());
}
else
// Get the watson buckets from the throwable for non-preallocated
// exceptions
pBuckets = dac_cast<PTR_VOID>(refWatsonBucketArray->GetDataPtr());
}
else
{
// This is a preallocated exception object - check if the UE Watson bucket tracker
// has any bucket details
pBuckets = pThread->GetExceptionState()->GetUEWatsonBucketTracker()->RetrieveWatsonBuckets();
if (pBuckets == NULL)
{
// This is a preallocated exception object - check if the UE Watson bucket tracker
// has any bucket details
pBuckets = pThread->GetExceptionState()->GetUEWatsonBucketTracker()->RetrieveWatsonBuckets();
if (pBuckets == NULL)
// Since the UE watson bucket tracker does not have them, look up the current
// exception tracker
if (pThread->GetExceptionState()->GetCurrentExceptionTracker() != NULL)
{
// Since the UE watson bucket tracker does not have them, look up the current
// exception tracker
if (pThread->GetExceptionState()->GetCurrentExceptionTracker() != NULL)
{
pBuckets = pThread->GetExceptionState()->GetCurrentExceptionTracker()->GetWatsonBucketTracker()->RetrieveWatsonBuckets();
}
pBuckets = pThread->GetExceptionState()->GetCurrentExceptionTracker()->GetWatsonBucketTracker()->RetrieveWatsonBuckets();
}
}
}
Expand Down
10 changes: 8 additions & 2 deletions src/coreclr/debug/daccess/task.cpp
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Expand Up @@ -4556,13 +4556,17 @@ ClrDataExceptionState::GetPrevious(
{
if (m_prevExInfo)
{
// Pass the address of the ExInfo's m_exception field as the "handle".
// This is not a real GC handle — it is a target address of an OBJECTREF
// slot on the stack. It has the same lifetime as the ExInfo (both are
// invalidated by PopExInfos/ReleaseResources). See dacimpl.h comment.
*exState = new (nothrow)
ClrDataExceptionState(m_dac,
m_appDomain,
m_thread,
CLRDATA_EXCEPTION_DEFAULT,
m_prevExInfo,
m_prevExInfo->m_hThrowable,
(OBJECTHANDLE)dac_cast<TADDR>(&m_prevExInfo->m_exception),
m_prevExInfo->m_pPrevNestedInfo);
status = *exState ? S_OK : E_OUTOFMEMORY;
}
Expand Down Expand Up @@ -4920,13 +4924,15 @@ ClrDataExceptionState::NewFromThread(ClrDataAccess* dac,

exState = thread->GetExceptionState()->m_pCurrentTracker;

// Pass the address of the ExInfo's m_exception field as the "handle".
// See dacimpl.h comment on the throwable parameter.
exIf = new (nothrow)
ClrDataExceptionState(dac,
AppDomain::GetCurrentDomain(),
thread,
CLRDATA_EXCEPTION_DEFAULT,
exState,
exState->m_hThrowable,
(OBJECTHANDLE)dac_cast<TADDR>(&exState->m_exception),
exState->m_pPrevNestedInfo);
if (!exIf)
{
Expand Down
11 changes: 7 additions & 4 deletions src/coreclr/debug/ee/debugger.cpp
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Expand Up @@ -7867,11 +7867,14 @@ BOOL Debugger::ShouldSendCatchHandlerFound(Thread* pThread)
else
{
BOOL forceSendCatchHandlerFound = FALSE;
OBJECTHANDLE objHandle = pThread->GetThrowableAsHandle();
OBJECTHANDLE retrievedHandle = m_pForceCatchHandlerFoundEventsTable->Lookup(objHandle); //destroy handle
if (retrievedHandle != NULL)
OBJECTHANDLE objHandle = pThread->m_LastThrownObjectHandle;
if (objHandle != NULL)
{
forceSendCatchHandlerFound = TRUE;
OBJECTHANDLE retrievedHandle = m_pForceCatchHandlerFoundEventsTable->Lookup(objHandle);
if (retrievedHandle != NULL)
{
forceSendCatchHandlerFound = TRUE;
}
}
return forceSendCatchHandlerFound;
}
Expand Down
2 changes: 1 addition & 1 deletion src/coreclr/vm/datadescriptor/datadescriptor.inc
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Expand Up @@ -138,7 +138,7 @@ CDAC_TYPE_END(Exception)
CDAC_TYPE_BEGIN(ExceptionInfo)
CDAC_TYPE_INDETERMINATE(ExceptionInfo)
CDAC_TYPE_FIELD(ExceptionInfo, T_POINTER, PreviousNestedInfo, offsetof(ExInfo, m_pPrevNestedInfo))
CDAC_TYPE_FIELD(ExceptionInfo, TYPE(ObjectHandle), ThrownObjectHandle, offsetof(ExInfo, m_hThrowable))
CDAC_TYPE_FIELD(ExceptionInfo, T_POINTER, ThrownObject, offsetof(ExInfo, m_exception))
CDAC_TYPE_FIELD(ExceptionInfo, T_UINT32, ExceptionFlags, cdac_data<ExInfo>::ExceptionFlagsValue)
CDAC_TYPE_FIELD(ExceptionInfo, T_POINTER, StackLowBound, cdac_data<ExInfo>::StackLowBound)
CDAC_TYPE_FIELD(ExceptionInfo, T_POINTER, StackHighBound, cdac_data<ExInfo>::StackHighBound)
Expand Down
31 changes: 9 additions & 22 deletions src/coreclr/vm/eedbginterfaceimpl.cpp
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Expand Up @@ -239,15 +239,16 @@ OBJECTHANDLE EEDbgInterfaceImpl::GetThreadException(Thread *pThread)
}
CONTRACTL_END;

OBJECTHANDLE oh = pThread->GetThrowableAsHandle();

if (oh != NULL)
// The exception object is stored directly in ExInfo::m_exception (no handle).
// Return m_LastThrownObjectHandle which is kept in sync via SafeSetThrowables
// before any debugger notification fires. Assert this invariant in debug builds.
#ifdef _DEBUG
ExInfo* pTracker = pThread->GetExceptionState()->GetCurrentExceptionTracker();
if (pTracker != NULL && pTracker->m_exception != NULL && pThread->m_LastThrownObjectHandle != NULL)
{
return oh;
_ASSERTE(ObjectFromHandle(pThread->m_LastThrownObjectHandle) == pTracker->m_exception);
}

// Return the last thrown object if there's no current throwable.
// This logic is similar to UpdateCurrentThrowable().
#endif
return pThread->m_LastThrownObjectHandle;
}

Expand All @@ -261,21 +262,7 @@ bool EEDbgInterfaceImpl::IsThreadExceptionNull(Thread *pThread)
}
CONTRACTL_END;

//
// We're assuming that the handle on the
// thread is a strong handle and we're goona check it for
// NULL. We're also assuming something about the
// implementation of the handle here, too.
//
OBJECTHANDLE h = pThread->GetThrowableAsHandle();
if (h == NULL)
{
return true;
}

void *pThrowable = *((void**)h);

return (pThrowable == NULL);
return pThread->IsThrowableNull() && pThread->IsLastThrownObjectNull();
}

void EEDbgInterfaceImpl::ClearThreadException(Thread *pThread)
Expand Down
3 changes: 1 addition & 2 deletions src/coreclr/vm/eepolicy.cpp
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Expand Up @@ -789,8 +789,7 @@ void DECLSPEC_NORETURN EEPolicy::HandleFatalStackOverflow(EXCEPTION_POINTERS *pE
OBJECTHANDLE ohSO = CLRException::GetPreallocatedStackOverflowExceptionHandle();
if (ohSO != NULL)
{
pThread->SafeSetThrowables(ObjectFromHandle(ohSO)
DEBUG_ARG(ThreadExceptionState::STEC_CurrentTrackerEqualNullOkHackForFatalStackOverflow),
pThread->SafeSetThrowables(ObjectFromHandle(ohSO),
TRUE);
}
else
Expand Down
4 changes: 2 additions & 2 deletions src/coreclr/vm/excep.cpp
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Expand Up @@ -1849,7 +1849,7 @@ BOOL IsInFirstFrameOfHandler(Thread *pThread, IJitManager *pJitManager, const ME
CONTRACTL_END;

// if don't have a throwable the aren't processing an exception
if (IsHandleNullUnchecked(pThread->GetThrowableAsHandle()))
if (pThread->IsThrowableNull())
return FALSE;

EH_CLAUSE_ENUMERATOR pEnumState;
Expand Down Expand Up @@ -2572,7 +2572,7 @@ void StackTraceInfo::AppendElement(OBJECTHANDLE hThrowable, UINT_PTR currentIP,
LOG((LF_EH, LL_INFO10000, "StackTraceInfo::AppendElement IP = %p, SP = %p, %s::%s\n", currentIP, currentSP, pFunc ? pFunc->m_pszDebugClassName : "", pFunc ? pFunc->m_pszDebugMethodName : "" ));

// Do not save stacktrace to preallocated exception. These are shared.
if (CLRException::IsPreallocatedExceptionHandle(hThrowable))
if (CLRException::IsPreallocatedExceptionObject(ObjectFromHandle(hThrowable)))
{
return;
}
Expand Down
28 changes: 14 additions & 14 deletions src/coreclr/vm/exceptionhandling.cpp
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Expand Up @@ -1447,7 +1447,9 @@ BOOL HandleHardwareException(PAL_SEHException* ex)
exInfo.TakeExceptionPointersOwnership(ex);
}

GCPROTECT_BEGIN(exInfo.m_exception);
// m_exception is GC-reported via ExInfo chain scanning in ScanStackRoots.
// Do NOT also GCPROTECT it — reporting the same location twice corrupts
// the GC's relocation logic (see clr-code-guide.md §2.1.5).
UnmanagedCallersOnlyCaller throwHwEx(METHOD__EH__RH_THROWHW_EX);

pThread->IncPreventAbort();
Expand All @@ -1457,8 +1459,6 @@ BOOL HandleHardwareException(PAL_SEHException* ex)

DispatchExSecondPass(&exInfo);

GCPROTECT_END();

UNREACHABLE();
}
else
Expand Down Expand Up @@ -1620,8 +1620,9 @@ VOID DECLSPEC_NORETURN DispatchManagedException(OBJECTREF throwable, CONTEXT* pE
}
}

GCPROTECT_BEGIN(exInfo.m_exception);

// m_exception is GC-reported via ExInfo chain scanning in ScanStackRoots.
// Do NOT also GCPROTECT it — reporting the same location twice corrupts
// the GC's relocation logic (see clr-code-guide.md §2.1.5).
UnmanagedCallersOnlyCaller throwEx(METHOD__EH__RH_THROW_EX);

pThread->IncPreventAbort();
Expand All @@ -1631,7 +1632,6 @@ VOID DECLSPEC_NORETURN DispatchManagedException(OBJECTREF throwable, CONTEXT* pE

DispatchExSecondPass(&exInfo);

GCPROTECT_END();
GCPROTECT_END();

UNREACHABLE();
Expand Down Expand Up @@ -1674,7 +1674,9 @@ VOID DECLSPEC_NORETURN DispatchRethrownManagedException(CONTEXT* pExceptionConte

ExInfo exInfo(pThread, pActiveExInfo->m_ptrs.ExceptionRecord, pExceptionContext, ExKind::None);

GCPROTECT_BEGIN(exInfo.m_exception);
// m_exception is GC-reported via ExInfo chain scanning in ScanStackRoots.
// Do NOT also GCPROTECT it — reporting the same location twice corrupts
// the GC's relocation logic (see clr-code-guide.md §2.1.5).
UnmanagedCallersOnlyCaller rethrow(METHOD__EH__RH_RETHROW);

pThread->IncPreventAbort();
Expand All @@ -1683,8 +1685,6 @@ VOID DECLSPEC_NORETURN DispatchRethrownManagedException(CONTEXT* pExceptionConte
rethrow.InvokeDirect(pActiveExInfo, &exInfo);
DispatchExSecondPass(&exInfo);

GCPROTECT_END();

UNREACHABLE();
}

Expand Down Expand Up @@ -2922,7 +2922,7 @@ ExInfo::StackRange::StackRange()
void ExInfo::EnumMemoryRegions(CLRDataEnumMemoryFlags flags)
{
// ExInfo is embedded so don't enum 'this'.
OBJECTHANDLE_EnumMemoryRegions(m_hThrowable);
OBJECTREF_EnumMemoryRegions(m_exception);
m_ptrs.ExceptionRecord.EnumMem();
m_ptrs.ContextRecord.EnumMem();
}
Expand Down Expand Up @@ -2973,7 +2973,7 @@ extern "C" void QCALLTYPE AppendExceptionStackFrame(QCall::ObjectHandleOnStack e
_ASSERTE(pMD == codeInfo.GetMethodDesc());
#endif // _DEBUG

StackTraceInfo::AppendElement(pExInfo->m_hThrowable, ip, sp, pMD, &pExInfo->m_frameIter.m_crawl);
StackTraceInfo::AppendElement((OBJECTHANDLE)&pExInfo->m_exception, ip, sp, pMD, &pExInfo->m_frameIter.m_crawl);
}
}

Expand Down Expand Up @@ -3772,7 +3772,7 @@ CLR_BOOL SfiInitWorker(StackFrameIterator* pThis, CONTEXT* pStackwalkCtx, CLR_BO
if (pMD != NULL)
{
GCX_COOP();
StackTraceInfo::AppendElement(pExInfo->m_hThrowable, 0, GetRegdisplaySP(pExInfo->m_frameIter.m_crawl.GetRegisterSet()), pMD, &pExInfo->m_frameIter.m_crawl);
StackTraceInfo::AppendElement((OBJECTHANDLE)&pExInfo->m_exception, 0, GetRegdisplaySP(pExInfo->m_frameIter.m_crawl.GetRegisterSet()), pMD, &pExInfo->m_frameIter.m_crawl);

#if defined(DEBUGGING_SUPPORTED)
if (NotifyDebuggerOfStub(pThread, pFrame))
Expand Down Expand Up @@ -3954,7 +3954,7 @@ CLR_BOOL SfiNextWorker(StackFrameIterator* pThis, uint* uExCollideClauseIdx, CLR
void* callbackCxt = NULL;
Interop::ManagedToNativeExceptionCallback callback = Interop::GetPropagatingExceptionCallback(
&codeInfo,
pTopExInfo->m_hThrowable,
pTopExInfo->m_exception,
&callbackCxt);

if (callback != NULL)
Expand Down Expand Up @@ -4091,7 +4091,7 @@ CLR_BOOL SfiNextWorker(StackFrameIterator* pThis, uint* uExCollideClauseIdx, CLR
if (pMD != NULL)
{
GCX_COOP();
StackTraceInfo::AppendElement(pTopExInfo->m_hThrowable, 0, GetRegdisplaySP(pTopExInfo->m_frameIter.m_crawl.GetRegisterSet()), pMD, &pTopExInfo->m_frameIter.m_crawl);
StackTraceInfo::AppendElement((OBJECTHANDLE)&pTopExInfo->m_exception, 0, GetRegdisplaySP(pTopExInfo->m_frameIter.m_crawl.GetRegisterSet()), pMD, &pTopExInfo->m_frameIter.m_crawl);

#if defined(DEBUGGING_SUPPORTED)
if (NotifyDebuggerOfStub(pThread, pFrame))
Expand Down
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