[cfe-dev] How to disable/override __builtin_operator_new/delete?

Thu Mar 22 14:00:51 PDT 2018

Hi Eric,

I'm trying to find the time to figure out a repo case for you to take a
look at.  Just got some xcode shenanigans to figure out.  :)

Our set up is as follows:

Static lib written in C++.  Our memory manager exists in here.
Framework (shared library) with mixed Swift and C++ code.  The global
new/delete operators are compiled here, and the static lib is linked in as
well.
App written in Swift.

As far as the callstack is concerned, it's basically this:

#0  __pthread_kill ()
#1  pthread_kill$VARIANT$mp ()
#2  abort ()
#3  free ()
#4  std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::~basic_string()

#5  The following five stack frames are in our C++ code...
#6
#7
#8
#9

#10 These four frames are Swift code in our framework...
#11
#12
#13

#14 -[UIApplication
_handleDelegateCallbacksWithOptions:isSuspended:restoreState:]
#15 -[UIApplication
_callInitializationDelegatesForMainScene:transitionContext:]
#16 -[UIApplication _runWithMainScene:transitionContext:completion:]
#17 __111-[__UICanvasLifecycleMonitor_Compatability
_scheduleFirstCommitForScene:transition:firstActivation:completion:]_block_invoke
#18 +[_UICanvas _enqueuePostSettingUpdateTransactionBlock:]
#19 -[__UICanvasLifecycleMonitor_Compatability
_scheduleFirstCommitForScene:transition:firstActivation:completion:]
#20 -[__UICanvasLifecycleMonitor_Compatability
activateEventsOnly:withContext:completion:]
#21 __82-[_UIApplicationCanvas
_transitionLifecycleStateWithTransitionContext:completion:]_block_invoke
#22 -[_UIApplicationCanvas
_transitionLifecycleStateWithTransitionContext:completion:]
#23 __125-[_UICanvasLifecycleSettingsDiffAction
performActionsForCanvas:withUpdatedScene:settingsDiff:fromSettings:transitionContext:]_block_invoke
#24 _performActionsWithDelayForTransitionContext
#25 -[_UICanvasLifecycleSettingsDiffAction
performActionsForCanvas:withUpdatedScene:settingsDiff:fromSettings:transitionContext:]
#26 -[_UICanvas scene:didUpdateWithDiff:transitionContext:completion:]
#27 -[UIApplication
workspace:didCreateScene:withTransitionContext:completion:]
#28 -[UIApplicationSceneClientAgent
scene:didInitializeWithEvent:completion:]
#29 -[FBSSceneImpl _didCreateWithTransitionContext:completion:]
#30 __56-[FBSWorkspace
client:handleCreateScene:withCompletion:]_block_invoke_2
#31 _dispatch_client_callout
#32 _dispatch_block_invoke_direct
#33 __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__
#34 -[FBSSerialQueue _performNext]
#35 -[FBSSerialQueue _performNextFromRunLoopSource]
#36 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__
#37 __CFRunLoopDoSource0
#38 __CFRunLoopDoSources0
#39 __CFRunLoopRun
#40 CFRunLoopRunSpecific
#41 GSEventRunModal
#42 UIApplicationMain
#43 main
#44 start

Nothing overly interesting to look at.  As I mentioned before, this happens
during application initialisation.

The output window in xcode simply has the following message:

malloc: *** error for objectt 0x1051bc0c0: pointer being freed was not
allocated

Which is partially correct.  It's a 176 byte memory block allocated by my
small block allocator.  (I just managed to track it down.)

I don't think the optimiser has anything to do with this.  This is
happening in debug builds.

It's smells like a compiler bug to me.  As I mentioned, the same code works
fine on both MacOS, Windows, and the iOS simulator (which basically will
compile to x86), so I would presume it's ARM specific - but that's merely a
guess by me here.

Cheers,
James

On 22 March 2018 at 05:31, Eric Fiselier <eric at efcs.ca> wrote:

> There is no way to disable __builtin_operator_new/delete or prevent libc++
> from using it.
>
> I would be interested to get some more details about your particular case.
> Ideally a reproducer
> I could play with. Or at least provide some sort of stack trace and error
> log.
>
> I'm not too familiar with the optimization aspects of
> __builtin_operator_new/delete, but the behavior
> you're observing sounds like a bug. Either in LLVM/Clang/libc++ or within
> your build. My suspicion
> is that an ODR violation is involved.
>
> /Eric
>
>
>
>
> On Wed, Mar 21, 2018 at 4:43 PM, James Robertson via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> Hi,
>>
>> I'm trying to get my own global operator new/delete calls working that my
>> memory manager plugs into.
>>
>> This code is working fine on MacOS (clang) and Windows (Visual Studio),
>> but on iOS I have a third party library (lohmann json) returning a
>> std::string object which appears to have been allocated through my
>> ::operator new function (I.e., my memory manager) but is being deleted
>> through __builtin_operator_delete.  Which just results in a crash almost
>> immediately after the app starts.
>>
>> So how do I disable these particular builtin functions?
>>
>> Cheers,
>> James
>>
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>
>>
>
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