[llvm-dev] Heap problems with 3.8.0rc2 in combination with vs2015 sp1
koffie drinker via llvm-dev
llvm-dev at lists.llvm.org
Fri Feb 26 00:59:09 PST 2016
Turns out llvm initializes memory before the constructor is invoked. Visual
studio has /sdl by default on, and the __autoclassinit2 will zero the
memory before the constructor is reached causing all the setters to be
default zero. which clears the hashungoff var and causing the delete to
flow in wrong part.
When /sdl is enabled, the compiler generates code to perform these checks
at run time:
— Performs class member initialization. *Automatically initializes all
class members to zero on object instantiation (before the constructor runs)*.
This helps prevent the use of uninitialized data associated with class
members that the constructor does not explicitly initialize.
Disabling the /SDL switch and everything works as intended. It might be
handy to put this in the windows docs since it costed me quite some time to
discover.
This is for reference to other users that are having heap issues:
http://stackoverflow.com/questions/25026488/c11-vs2013-class-pod-member-initialization
On Thu, Feb 25, 2016 at 4:33 PM, koffie drinker <gekkekoe at gmail.com> wrote:
> I found the root cause, but I don't know what's the best approach to fix
> it.
>
> Under windows, 64 bit, when a function is created the void *User::operator
> new(size_t Size) operator allocates space + Use*.
> In the Use* the HasHungOffUses is set to true. So the ptr to the use* is
> returned as new object. This ptr is NOT the ptr that was allocated by the
> system. For that ptr you need ptr - word length. It's important that we use
> free on the original ptr.
>
> The void User::operator delete(void *Usr) deletes the use* when dtor is
> called. However, tracing through the Function() ctor I see that the
> HasHungOffUses is set to False (!). And when we arrive at the
> User::delete, the HasHungOffUses has the wrong value causing it to flow
> into the else part.
>
> void User::operator delete(void *Usr) {
> // Hung off uses use a single Use* before the User, while other
> subclasses
> // use a Use[] allocated prior to the user.
> User *Obj = static_cast<User *>(Usr);
> if (Obj->HasHungOffUses) {
> assert(!Obj->HasDescriptor && "not supported!");
>
> Use **HungOffOperandList = static_cast<Use **>(Usr) - 1;
> // drop the hung off uses.
> Use::zap(*HungOffOperandList, *HungOffOperandList +
> Obj->NumUserOperands,
> /* Delete */ true);
> ::operator delete(HungOffOperandList);
> } else if (Obj->HasDescriptor) {
> Use *UseBegin = static_cast<Use *>(Usr) - Obj->NumUserOperands;
> Use::zap(UseBegin, UseBegin + Obj->NumUserOperands, /* Delete */
> false);
>
> auto *DI = reinterpret_cast<DescriptorInfo *>(UseBegin) - 1;
> uint8_t *Storage = reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes;
> ::operator delete(Storage);
> } else {
> Use *Storage = static_cast<Use *>(Usr) - Obj->NumUserOperands;
> Use::zap(Storage, Storage + Obj->NumUserOperands,
> /* Delete */ false);
> ::operator delete(Storage);
> }
> }
>
> The storage address is computed wrongly in this case, it's off by 1 word
> length. And so visual studio sees that I'm not freeing the org allocated
> ptr and throws heap error. During debug when I force HasHungOffUses = true,
> everything is fine and the correct original ptr is computed and freed. So
> I'm guessing that that value should have stayed true.
>
> I also have set a data breakpoint on HashHungOffUses when it's accessed
> and did noticed that
> ConsoleEngine.exe!llvm::Function::__autoclassinit2(unsigned __int64) C++
> ConsoleEngine.exe!llvm::Function::Create(llvm::FunctionType * Ty,
> llvm::GlobalValue::LinkageTypes Linkage, const llvm::Twine & N,
> llvm::Module * M) Line 116 C++
>
> caused it to be set to False. So do I need to trace into all the Function
> bases classes and find out where it is set to false? or do I need to fix
> the Storage address computation in the else part?
>
> Cheers,
>
>
> On Thu, Feb 25, 2016 at 1:07 PM, koffie drinker <gekkekoe at gmail.com>
> wrote:
>
>> I made the llvm::Function() constructor public (for testing purpose) and
>> used the non-overloaded new.
>>
>> auto func = ::new llvm::Function(...)
>> if (func) func->eraseFromParent();
>>
>> And the heap corruption is gone! Did something changed in llvm::User::new
>> between 3.7.1 and 3.8.0 ?
>> I found a bug in llvm ?
>>
>>
>> On Thu, Feb 25, 2016 at 12:10 PM, koffie drinker <gekkekoe at gmail.com>
>> wrote:
>>
>>> I downloaded 3.8.0rc3 and I also have it in 3.8.0rc3.
>>> I did set a data access breakpoint on the first function ptr that causes
>>> the invalid heap. This would allow me to break whenever someone is touching
>>> that address. It did not show double deletes during debugging. Further more
>>> I managed to narrow it down to 2 function calls:
>>>
>>> // stupid code, but its just for triggering heap error
>>> auto func = llvm::Function::Create(...);
>>> if (func) func->eraseFromParent();
>>>
>>> The erase from parent triggers the invalid heap. I used appverif.exe and
>>> gflags.exe (page heap checks) but they could not find anything.
>>> The Function::Create is just a wrapper for new Function(). I also traced
>>> into this call, but did not see anything weird. It returns a valid ptr.
>>> Somehow the ptr returned by the new seems to be broken. If i'm not
>>> mistaken the new operator is overloaded by llvm? I could not try to use the
>>> default new Function() since its constructor is not accessible from outside.
>>>
>>> I'm kinda lost where to look next. There's not much that could go wrong
>>> with creating a function and deleting it?
>>> I'm using visual studio 2015 update1, and could not find any known issue
>>> regarding heaps. I'm at a point where I'm suspecting my compiler.
>>> But its weird that the same compiler works fine with 3.7.1
>>>
>>> any ideas would be appreciated
>>>
>>>
>>> On Wed, Feb 24, 2016 at 9:10 AM, koffie drinker <gekkekoe at gmail.com>
>>> wrote:
>>>
>>>>
>>>> I recently upgraded from llvm 3.7.1 to a pre release of llvm (3.8.0rc2)
>>>> in order to test some issues regarding bug 24233.
>>>> After upgrading I starting to see heap corruption messages in vs 2015
>>>> sp1 when my program exits.
>>>> "HEAP[ConsoleEngine.exe]: Invalid address specified to RtlValidateHeap(
>>>> 0000000000290000, 0000000000318698 )"
>>>>
>>>> Initially I only got it in Release build. Debug build seems to be fine,
>>>> but recently I also got them in Debug build.
>>>> I traced it down how to trigger it in Debug Mode. It happens when I put
>>>> the ExecutionEngine creation in the constructor in the cpp file.
>>>> If I put it in the h file then there's no problem. This leads me to
>>>> believe that it is probably not my code that is causing it since I never
>>>> seem to have
>>>> this issue in the past (3.6.x - 3.7.x). I've include the stack traces
>>>> below this email.
>>>>
>>>> It fails when the dtor is called for the first module. MCJIT only has 2
>>>> modules, the first one only has function declarations. The second one is
>>>> empty. No codegen is taking place.
>>>>
>>>> I googled for the error message and it seems to be happen when you
>>>> delete a resource twice.
>>>> Did something change for 3.8.0 regarding to function decl. creation in
>>>> a module? Any tips on how to trace it down further? I can't seem to make a
>>>> small example demonstration the problem. It only seems to be triggered in a
>>>> larger project (again: nearly code works fine in 3.6.x-3.7.x)
>>>>
>>>>
>>>> -- Release mode stack trace
>>>> ntdll.dll!RtlReportCriticalFailure() Unknown
>>>> ntdll.dll!RtlpReportHeapFailure() Unknown
>>>> ntdll.dll!RtlpHeapHandleError() Unknown
>>>> ntdll.dll!RtlpLogHeapFailure() Unknown
>>>> ntdll.dll!string "Enabling heap debug options\n"() Unknown
>>>> ucrtbase.dll!free() Unknown
>>>> ConsoleEngine.exe!llvm::Function::`vector deleting
>>>> destructor'(unsigned int) C++
>>>> ConsoleEngine.exe!llvm::Module::~Module(void) C++
>>>> ConsoleEngine.exe!llvm::MCJIT::OwningModuleContainer::freeModulePtrSet(class
>>>> llvm::SmallPtrSet<class llvm::Module *,4> &) C++
>>>> ConsoleEngine.exe!llvm::MCJIT::~MCJIT(void) C++
>>>> ConsoleEngine.exe!llvm::MCJIT::`vector deleting destructor'(unsigned
>>>> int) C++
>>>>
>>>> -- Debug Mode stack trace
>>>> ntdll.dll!RtlpBreakPointHeap() Unknown
>>>> ntdll.dll!string "Enabling heap debug options\n"() Unknown
>>>> ntdll.dll!RtlValidateHeap() Unknown
>>>> KernelBase.dll!HeapValidate() Unknown
>>>> ucrtbased.dll!_CrtIsValidHeapPointer() Unknown
>>>> ucrtbased.dll!_calloc_base() Unknown
>>>> ucrtbased.dll!_free_dbg() Unknown
>>>> ConsoleEngine.exe!operator delete(void * block) Line 21 C++
>>>> ConsoleEngine.exe!llvm::User::operator delete(void * Usr) Line 195 C++
>>>> ConsoleEngine.exe!llvm::Function::`scalar deleting
>>>> destructor'(unsigned int) C++
>>>> ConsoleEngine.exe!llvm::ilist_node_traits<llvm::Function>::deleteNode(llvm::Function
>>>> * V) Line 160 C++
>>>> ConsoleEngine.exe!llvm::iplist<llvm::Function,llvm::SymbolTableListTraits<llvm::Function>
>>>> >::erase(llvm::ilist_iterator<llvm::Function> where) Line 519 C++
>>>> ConsoleEngine.exe!llvm::iplist<llvm::Function,llvm::SymbolTableListTraits<llvm::Function>
>>>> >::erase(llvm::ilist_iterator<llvm::Function> first,
>>>> llvm::ilist_iterator<llvm::Function> last) Line 601 C++
>>>> ConsoleEngine.exe!llvm::iplist<llvm::Function,llvm::SymbolTableListTraits<llvm::Function>
>>>> >::clear() Line 605 C++
>>>> ConsoleEngine.exe!llvm::Module::~Module() Line 61 C++
>>>> ConsoleEngine.exe!llvm::Module::`scalar deleting
>>>> destructor'(unsigned int) C++
>>>> ConsoleEngine.exe!llvm::MCJIT::OwningModuleContainer::freeModulePtrSet(llvm::SmallPtrSet<llvm::Module
>>>> *,4> & MPS) Line 175 C++
>>>> ConsoleEngine.exe!llvm::MCJIT::OwningModuleContainer::~OwningModuleContainer()
>>>> Line 82 C++
>>>> ConsoleEngine.exe!llvm::MCJIT::~MCJIT() Line 102 C++
>>>> ConsoleEngine.exe!llvm::MCJIT::`scalar deleting destructor'(unsigned
>>>> int) C++
>>>> ConsoleEngine.exe!std::default_delete<llvm::ExecutionEngine>::operator()(llvm::ExecutionEngine
>>>> * _Ptr) Line 1195 C++
>>>> ConsoleEngine.exe!std::unique_ptr<llvm::ExecutionEngine,std::default_delete<llvm::ExecutionEngine>
>>>> >::~unique_ptr<llvm::ExecutionEngine,std::default_delete<llvm::ExecutionEngine>
>>>> >() Line 1398 C++
>>>>
>>>>
>>>
>>
>
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