Presumably this:
https://source.chromium.org/chromium/chromium/src/+/main:v8/include/v8-memory-span.h;l=124;drc=d350ca68909171a740a8e33c43fea86ed0574a05
just needs to be:
: data_(first == last ? nullptr : to_address(first)), size_(last - first) {}
?
On Thursday, 26 June 2025 at 18:45:04 UTC+1 niko...@google.com wrote:
> The problem arises at this point
> <https://source.chromium.org/chromium/chromium/src/+/main:v8/src/compiler/js-heap-broker.cc;drc=ef9dafb5ab5b78fef65ce358dd92c2b60d69cee5;l=882>,
>
> when possible_transition_targets is empty.
>
> It seems that the following program runs successfully with clang, both in
> Linux and Windows.
> However, it fails with MSVC, exactly with the assertion failure that
> you're getting.
>
> #include <cassert>
> #include <vector>
>
> int main() {
> std::vector < int> empty;
> assert(nullptr == empty.begin().operator->());
> }
>
> I will investigate some more and come back with a fix.
> Thank you for reporting!
>
> On Wednesday, June 25, 2025 at 9:57:43 PM UTC+2 audrius.b...@gmail.com
> wrote:
>
>> Seems that I've hit the same case without Maglev:
>>
>> ==== C stack trace ===============================
>>
>>
>> std::_Vector_iterator<std::_Vector_val<std::_Simple_types<std::pair<int,v8::internal::Tagged<v8::internal::HeapObject>
>>
>> > > > >::operator-> [0x00007FFB8C978EB1+369]
>> v8::MemorySpan<v8::internal::Handle<v8::internal::Map>
>> >::to_address<std::_Vector_iterator<std::_Vector_val<std::_Simple_types<v8::internal::Handle<v8::internal::Map>
>> >
>> > > >,void> [0x00007FFB8D13EC83+19]
>> v8::MemorySpan<v8::internal::Handle<v8::internal::Map>
>> >::MemorySpan<v8::internal::Handle<v8::internal::Map>
>> ><std::_Vector_iterator<std::_Vector_val<std::_Simple_types<v8::internal::Handle<v8::internal::Map>
>> >
>> > > >,1> [0x00007FFB8D13E704+52]
>>
>> v8::internal::compiler::JSHeapBroker::ProcessFeedbackMapsForElementAccess
>> [0x00007FFB8E57704A+714]
>>
>> v8::internal::compiler::JSHeapBroker::ReadFeedbackForPropertyAccess
>> [0x00007FFB8E5788E1+1841]
>>
>> v8::internal::compiler::JSHeapBroker::GetFeedbackForPropertyAccess
>> [0x00007FFB8E573848+88]
>>
>> v8::internal::compiler::JSNativeContextSpecialization::ReducePropertyAccess
>> [0x00007FFB8EB83319+681]
>>
>> v8::internal::compiler::JSNativeContextSpecialization::ReduceJSSetKeyedProperty
>>
>> [0x00007FFB8EB7EF21+321]
>> v8::internal::compiler::JSNativeContextSpecialization::Reduce
>> [0x00007FFB8EB73019+649]
>> v8::internal::compiler::Reducer::Reduce [0x00007FFB8E93D1EC+60]
>> v8::internal::compiler::GraphReducer::Reduce
>> [0x00007FFB8E93CEBE+190]
>> v8::internal::compiler::GraphReducer::ReduceTop
>> [0x00007FFB8E93D708+600]
>> v8::internal::compiler::GraphReducer::ReduceNode
>> [0x00007FFB8E93D32E+174]
>> v8::internal::compiler::GraphReducer::ReduceGraph
>> [0x00007FFB8E93D278+40]
>> v8::internal::compiler::InliningPhase::Run
>> [0x00007FFB8E4E7CBE+1950]
>>
>> v8::internal::compiler::PipelineImpl::Run<v8::internal::compiler::InliningPhase>
>>
>> [0x00007FFB8E49B71B+123]
>> v8::internal::compiler::PipelineImpl::CreateGraph
>> [0x00007FFB8E4D03C8+168]
>> v8::internal::compiler::PipelineCompilationJob::ExecuteJobImpl
>> [0x00007FFB8E4D205C+428]
>> v8::internal::OptimizedCompilationJob::ExecuteJob
>> [0x00007FFB8CB5E11B+299]
>> v8::internal::OptimizingCompileDispatcher::CompileNext
>> [0x00007FFB8D0390A3+67]
>> v8::internal::OptimizingCompileDispatcher::CompileTask::Run
>> [0x00007FFB8D03A2F9+633]
>> v8::platform::DefaultJobWorker::Run [0x00007FFB8CD835F9+185]
>> v8::platform::DefaultWorkerThreadsTaskRunner::WorkerThread::Run
>> [0x00007FFB8CD83E72+194]
>> v8::base::Thread::NotifyStartedAndRun [0x00007FFB8C6D8904+52]
>> v8::base::OS::StrNCpy [0x00007FFB8C6D964D+205]
>> thread_start<unsigned int (__cdecl*)(void *),1>
>> [0x00007FFB8F67B6B5+165]
>> (minkernel\crts\ucrt\src\appcrt\startup\thread.cpp:97)
>> BaseThreadInitThunk [0x00007FFCBDDA7374+20]
>> RtlUserThreadStart [0x00007FFCBFDBCC91+33]
>>
>> I suspect this thread is what triggered it:
>>
>> 0 # NtWaitForAlertByThreadId in ntdll+0xa0f24
>> 1 # RtlAcquireSRWLockExclusive in ntdll+0x29205
>> 2 # v8::base::SharedMutex::LockExclusive in app+0x59258f
>> 3 #
>> `v8::internal::ParkedSharedMutexGuardIf<1,0>::ParkedSharedMutexGuardIf<1,0>'::`25'::<lambda_2>::operator()
>>
>> in app+0xea0a99
>> 4 #
>> v8::internal::LocalHeap::ParkAndExecuteCallback<`v8::internal::ParkedSharedMutexGuardIf<1,0>::ParkedSharedMutexGuardIf<1,0>'::`25'::<lambda_2>
>>
>> > in app+0xe9f7c8
>> 5 #
>> `v8::internal::LocalHeap::ExecuteWhileParked<`v8::internal::ParkedSharedMutexGuardIf<1,0>::ParkedSharedMutexGuardIf<1,0>'::`25'::<lambda_2>
>>
>> >'::`2'::<lambda_1>::operator() in app+0xea0749
>> 6 #
>> heap::base::Stack::SetMarkerAndCallbackImpl<`v8::internal::LocalHeap::ExecuteWhileParked<`v8::internal::ParkedSharedMutexGuardIf<1,0>::ParkedSharedMutexGuardIf<1,0>'::`25'::<lambda_2>
>>
>> >'::`2'::<lambda_1> > in app+0xe9f99b
>> 7 # PushAllRegistersAndIterateStack in app+0xf65abd
>> 8 # heap::base::Stack::TrampolineCallbackHelper in app+0x7f3737
>> 9 #
>> heap::base::Stack::SetMarkerAndCallback<`v8::internal::LocalHeap::ExecuteWhileParked<`v8::internal::ParkedSharedMutexGuardIf<1,0>::ParkedSharedMutexGuardIf<1,0>'::`25'::<lambda_2>
>>
>> >'::`2'::<lambda_1> > in app+0xe9f8d4
>> 10 #
>> v8::internal::LocalHeap::ExecuteWithStackMarker<`v8::internal::LocalHeap::ExecuteWhileParked<`v8::internal::ParkedSharedMutexGuardIf<1,0>::ParkedSharedMutexGuardIf<1,0>'::`25'::<lambda_2>
>>
>> >'::`2'::<lambda_1> > in app+0xe9edfe
>> 11 #
>> v8::internal::LocalHeap::ExecuteWhileParked<`v8::internal::ParkedSharedMutexGuardIf<1,0>::ParkedSharedMutexGuardIf<1,0>'::`25'::<lambda_2>
>>
>> > in app+0xe9ec55
>> 12 #
>> v8::internal::ParkedSharedMutexGuardIf<0,0>::ParkedSharedMutexGuardIf<0,0>
>> in app+0xea01dd
>> 13 #
>> v8::internal::ParkedSharedMutexGuardIf<0,0>::ParkedSharedMutexGuardIf<0,0>
>> in app+0xea022a
>> 14 # v8::internal::MapUpdater::ReconfigureToDataField in app+0xeaaa4d
>> 15 # v8::internal::Map::Update in app+0x80f4c7
>> 16 # v8::internal::Map::TransitionToDataProperty in app+0x80cf20
>> 17 # v8::internal::LookupIterator::PrepareTransitionToDataProperty in
>> app+0x9d3cc5
>> 18 # v8::internal::Object::TransitionAndWriteDataProperty in
>> app+0x642167
>> 19 # v8::internal::Object::AddDataProperty in app+0x5fc92e
>> 20 # v8::internal::JSObject::DefineOwnPropertyIgnoreAttributes in
>> app+0x754a99
>> 21 # v8::internal::JSObject::DefineOwnPropertyIgnoreAttributes in
>> app+0x754b5e
>> 22 # v8::internal::JSObject::SetOwnPropertyIgnoreAttributes in
>> app+0x778e02
>> 23 #
>> v8::internal::CastTraits<v8::internal::ObjectBoilerplateDescription>::AllowFrom
>>
>> in app+0x1fd8252
>> 24 #
>> v8::internal::CastTraits<v8::internal::ObjectBoilerplateDescription>::AllowFrom
>>
>> in app+0x1fd6f4a
>> 25 #
>> v8::internal::Cast<v8::internal::ObjectBoilerplateDescription,v8::internal::Object>
>>
>> in app+0x1fd6c66
>> 26 #
>> v8::internal::Cast<v8::internal::ObjectBoilerplateDescription,v8::internal::Object>
>>
>> in app+0x1fd65d7
>> 27 # v8::internal::AllocationSiteUsageContext::ShouldCreateMemento in
>> app+0x1fe14a8
>> 28 # v8::internal::Runtime_CreateObjectLiteral in app+0x1fd93b4
>> On Wednesday, 25 June 2025 at 17:16:00 UTC+1 Audrius Butkevicius wrote:
>>
>>> I've actually posted stacktraces of other threads on the user list (
>>> https://groups.google.com/g/v8-users/c/iaD_4IGqIyI) which hints this is
>>> a race condition.
>>> Seems that the code on head hasn't changed around this, so it still
>>> might be a bug now, but confirmed, the issue goes away by switching off
>>> maglev.
>>>
>>> On Wednesday, 25 June 2025 at 13:55:06 UTC+1 in...@bnoordhuis.nl wrote:
>>>
>>>> On Wed, Jun 25, 2025 at 2:11 PM Audrius Butkevicius
>>>> <audrius.b...@gmail.com> wrote:
>>>> >
>>>> > Hi
>>>> >
>>>> > I'm running my application in debug mode, and I noticed it sometimes
>>>> it fails with his assert:
>>>> >
>>>> > C:\Program Files\Microsoft Visual
>>>> Studio\2022\Community\VC\Tools\MSVC\14.43.34808\include\vector(280) :
>>>> Assertion failed: can't dereference out of range vector iterator
>>>> >
>>>> > ...
>>>> >
>>>> > 3 # `DllMain'::`5'::<lambda_1>::operator() at dllmain.cpp:598
>>>> (app+0x371a7cd)
>>>> > 4 # `DllMain'::`5'::<lambda_1>::<lambda_invoker_cdecl> at
>>>> dllmain.cpp:614 (app+0x371a668)
>>>> > 5 # _VCrtDbgReportA at dbgrptt.cpp:391 (app+0x361df8f)
>>>> > 6 # _CrtDbgReport at dbgrpt.cpp:263 (app+0x35ee779)
>>>> > 7 #
>>>> std::_Vector_iterator<std::_Vector_val<std::_Simple_types<std::pair<int,v8::internal::Tagged<v8::internal::HeapObject>
>>>>
>>>> > > > >::operator-> in app+0x92054c
>>>> > 8 # v8::MemorySpan<v8::internal::Handle<v8::internal::Map>
>>>> >::to_address<std::_Vector_iterator<std::_Vector_val<std::_Simple_types<v8::internal::Handle<v8::internal::Map>
>>>> >
>>>> > > >,void> in app+0x10e5643
>>>> > 9 # v8::MemorySpan<v8::internal::Handle<v8::internal::Map>
>>>> >::MemorySpan<v8::internal::Handle<v8::internal::Map>
>>>> ><std::_Vector_iterator<std::_Vector_val<std::_Simple_types<v8::internal::Handle<v8::internal::Map>
>>>> >
>>>> > > >,1> in app+0x10e50c4
>>>> > 10 #
>>>> v8::internal::compiler::JSHeapBroker::ProcessFeedbackMapsForElementAccess
>>>> in app+0x251e77a
>>>> > 11 #
>>>> v8::internal::compiler::JSHeapBroker::ReadFeedbackForPropertyAccess in
>>>> app+0x2520011
>>>> > 12 #
>>>> v8::internal::compiler::JSHeapBroker::GetFeedbackForPropertyAccess in
>>>> app+0x251af78
>>>> > 13 # v8::internal::maglev::MaglevGraphBuilder::VisitStaInArrayLiteral
>>>> in app+0x2862834
>>>> > 14 # v8::internal::maglev::MaglevGraphBuilder::VisitSingleBytecode in
>>>> app+0x2343e8f
>>>> > 15 # v8::internal::maglev::MaglevGraphBuilder::BuildBody in
>>>> app+0x230b567
>>>> > 16 # v8::internal::maglev::MaglevGraphBuilder::Build in app+0x230b385
>>>> > 17 # v8::internal::maglev::MaglevCompiler::Compile in app+0x230bd91
>>>> > 18 # v8::internal::maglev::MaglevCompilationJob::ExecuteJobImpl in
>>>> app+0xfe89b8
>>>> > 19 # v8::internal::OptimizedCompilationJob::ExecuteJob in
>>>> app+0xb0583b
>>>> > 20 # v8::internal::maglev::MaglevConcurrentDispatcher::JobTask::Run
>>>> in app+0xfe9c23
>>>> > 21 # v8::platform::DefaultJobWorker::Run in app+0xd2a949
>>>> > 22 # v8::platform::DefaultWorkerThreadsTaskRunner::WorkerThread::Run
>>>> in app+0xd2b1c2
>>>> > 23 # v8::base::Thread::NotifyStartedAndRun in app+0x681104
>>>> > 24 # v8::base::OS::StrNCpy in app+0x681e4d
>>>> > 25 # thread_start<unsigned int (__cdecl*)(void *),1> at thread.cpp:97
>>>> (app+0x3622e45)
>>>> > 26 # BaseThreadInitThunk in KERNEL32+0x17374
>>>> > 27 # RtlUserThreadStart in ntdll+0x4cc91
>>>> >
>>>> > It's possible that I'm doing something wrong, but it's not very clear
>>>> what.
>>>> >
>>>> > Sadly, this is version 12.9.202, as I still need a static build that
>>>> uses MSVC.
>>>> >
>>>> > Any suggestions would be welcome, as to what I'm doing wrong.
>>>> >
>>>> > Thanks.
>>>>
>>>> Maybe try building with v8_enable_maglev=false. In node, we had maglev
>>>> disabled until at least 12.8 because of various crashes.
>>>>
>>>
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