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We recently released a game on iOS and Android, and a bunch of crash reports have started coming in on iOS through Crashlytics that appear to be due to problems with shaders in asset bundles and other asset bundle problems (such as loading models, textures, basically anything and everything in an asset bundle). We haven't been able to reproduce this problem, so we aren't sure what we can do about them other than do a new release with new builds of the asset bundles and hope that they work. We're using Unity 2108.2.12f1.

Is there anything we can do to try to resolve this problem?

For reference, here are some of the places where it has crashed. All of these are internal to Unity apparently. There's nothing specific to our game in the stack trace. I'm not sure how useful these different stack traces are.

Crashed: UnityPreload EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000000000000 __bzero + 28 SerializeTraits.h - Line 488 SerializeTraits<dynamic_array<unsigned char, 0ul> >::ResizeSTLStyleArray(dynamic_array<unsigned char, 0ul>&, int) StreamedBinaryRead.h - Line 77 void StreamedBinaryRead::TransferSTLStyleArray<dynamic_array<unsigned char, 0ul> >(dynamic_array<unsigned char, 0ul>&, TransferMetaFlags) SerializeTraits.h - Line 481 void PackedFloatVector::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) CompressedMesh.h - Line 155 void CompressedMesh::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) SerializeTraitsBase.h - Line 54 void Mesh::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) SerializedFile.cpp - Line 2164 SerializedFile::ReadObject(long long, ObjectCreationMode, bool, TypeTree const**, bool*, Object&) PersistentManager.cpp - Line 2330 PersistentManager::ReadAndActivateObjectThreaded(int, SerializedObjectIdentifier const&, SerializedFile*, bool, bool, PersistentManager::LockFlags) PersistentManager.cpp - Line 1785 PersistentManager::LoadObjectsThreaded(int const*, int, LoadProgress&, bool) dynamic_array.h - Line 146 LoadSceneOperation::perform() PreloadManager.cpp - Line 281 PreloadManager::processSingleOperation() PreloadManager.cpp - Line 338 PreloadManager::Run() PreloadManager.cpp - Line 187 PreloadManager::Run(void*) Thread.cpp - Line 42 Thread::RunThreadWrapper(void*)

And a dozen similar ones.

Crashed: UnityPreload EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000000000028 StringStorageDefault.h - Line 31 std::__1::vector<ShaderLab::SerializedSubProgram::StructParameter, std::__1::allocator<ShaderLab::SerializedSubProgram::StructParameter> >::__append(unsigned long) type_traits - Line 3615 void resize_trimmed<std::__1::vector<ShaderLab::SerializedSubProgram::StructParameter, std::__1::allocator<ShaderLab::SerializedSubProgram::StructParameter> > >(std::__1::vector<ShaderLab::SerializedSubProgram::StructParameter, std::__1::allocator<ShaderLab::SerializedSubProgram::StructParameter> >&, unsigned int) vector - Line 1467 void StreamedBinaryRead::TransferSTLStyleArray<std::__1::vector<ShaderLab::SerializedSubProgram::StructParameter, std::__1::allocator<ShaderLab::SerializedSubProgram::StructParameter> > >(std::__1::vector<ShaderLab::SerializedSubProgram::StructParameter, std::__1::allocator<ShaderLab::SerializedSubProgram::StructParameter> >&, TransferMetaFlags) SerializeTraits.h - Line 260 void ShaderLab::SerializedSubProgram::ConstantBuffer::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) iterator - Line 1190 void StreamedBinaryRead::TransferSTLStyleArray<std::__1::vector<ShaderLab::SerializedSubProgram::ConstantBuffer, std::__1::allocator<ShaderLab::SerializedSubProgram::ConstantBuffer> > >(std::__1::vector<ShaderLab::SerializedSubProgram::ConstantBuffer, std::__1::allocator<ShaderLab::SerializedSubProgram::ConstantBuffer> >&, TransferMetaFlags) SerializeTraits.h - Line 260 void ShaderLab::SerializedSubProgram::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) iterator - Line 1190 void StreamedBinaryRead::TransferSTLStyleArray<std::__1::vector<ShaderLab::SerializedSubProgram, std::__1::allocator<ShaderLab::SerializedSubProgram> > >(std::__1::vector<ShaderLab::SerializedSubProgram, std::__1::allocator<ShaderLab::SerializedSubProgram> >&, TransferMetaFlags) SerializeTraits.h - Line 260 void ShaderLab::SerializedPass::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) iterator - Line 1190 void StreamedBinaryRead::TransferSTLStyleArray<std::__1::vector<ShaderLab::SerializedPass, std::__1::allocator<ShaderLab::SerializedPass> > >(std::__1::vector<ShaderLab::SerializedPass, std::__1::allocator<ShaderLab::SerializedPass> >&, TransferMetaFlags) SerializeTraits.h - Line 260 void ShaderLab::SerializedSubShader::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) iterator - Line 1190 void StreamedBinaryRead::TransferSTLStyleArray<std::__1::vector<ShaderLab::SerializedSubShader, std::__1::allocator<ShaderLab::SerializedSubShader> > >(std::__1::vector<ShaderLab::SerializedSubShader, std::__1::allocator<ShaderLab::SerializedSubShader> >&, TransferMetaFlags) SerializeTraits.h - Line 260 void ShaderLab::SerializedShader::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) SerializeTraits.h - Line 480 void Shader::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) SerializedFile.cpp - Line 2164 SerializedFile::ReadObject(long long, ObjectCreationMode, bool, TypeTree const**, bool*, Object&) PersistentManager.cpp - Line 2330 PersistentManager::ReadAndActivateObjectThreaded(int, SerializedObjectIdentifier const&, SerializedFile*, bool, bool, PersistentManager::LockFlags) PersistentManager.cpp - Line 1785 PersistentManager::LoadObjectsThreaded(int const*, int, LoadProgress&, bool) dynamic_array.h - Line 146 LoadSceneOperation::perform() PreloadManager.cpp - Line 281 PreloadManager::processSingleOperation() PreloadManager.cpp - Line 338 PreloadManager::Run() PreloadManager.cpp - Line 187 PreloadManager::Run(void*) Thread.cpp - Line 42 Thread::RunThreadWrapper(void*)

And a dozen similar ones

Crashed: com.apple.main-thread EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x00000000b253c034 libsystem_platform.dylib _platform_memmove + 352 CachedReader.cpp - Line 98 CachedReader::Read(void*, unsigned long) StreamedBinaryRead.h - Line 88 void StreamedBinaryRead::TransferSTLStyleArray<core::basic_string<char, core::StringStorageDefault<char> > >(core::basic_string<char, core::StringStorageDefault<char> >&, TransferMetaFlags) SerializeTraits.h - Line 237 void NamedObject::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) SpriteFrame.cpp - Line 134 void Sprite::Transfer<StreamedBinaryRead>(StreamedBinaryRead&) SerializedFile.cpp - Line 2164 SerializedFile::ReadObject(long long, ObjectCreationMode, bool, TypeTree const**, bool*, Object&) PersistentManager.cpp - Line 2330 PersistentManager::ReadAndActivateObjectThreaded(int, SerializedObjectIdentifier const&, SerializedFile*, bool, bool, PersistentManager::LockFlags) PersistentManager.cpp - Line 1663 PersistentManager::ReadObjectThreaded(int, PersistentManager::LockFlags) PersistentManager.cpp - Line 1390 PersistentManager::ReadObject(int, AwakeFromLoadMode) AssetBundleUtility.cpp - Line 143 ForcePreload(AssetBundle&, dynamic_array<int, 0ul>, bool) dynamic_array.h - Line 114 ProcessAssetBundleEntries(AssetBundle&, std::__1::pair<std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::__value_type<core::basic_string<char, core::StringStorageDefault<char> >, AssetBundle::AssetInfo>, std::__1::__tree_node<std::__1::__value_type<core::basic_string<char, core::StringStorageDefault<char> >, AssetBundle::AssetInfo>, void*>*, long> >, std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::__value_type<core::basic_string<char, core::StringStorageDefault<char> >, AssetBundle::AssetInfo>, std::__1::__tree_node<std::__1::__value_type<core::basic_string<char, core::StringStorageDefault<char> >, AssetBundle::AssetInfo>, void*>*, long> > > const&, ScriptingSystemTypeObjectPtr, dynamic_array<Object*, 0ul>&, bool) dynamic_array.h - Line 471 LoadNamedObjectFromAssetBundle(AssetBundle&, core::basic_string<char, core::StringStorageDefault<char> > const&, ScriptingSystemTypeObjectPtr) AssetBundle.bindings.gen.cpp - Line 265 AssetBundle_CUSTOM_LoadAsset_Internal(Il2CppObject*, Il2CppString*, Il2CppObject*) unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 3860516 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 7811508 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 21918336 Il2CppInvokerTable.cpp - Line 4336374932 RuntimeInvoker_Void_t1185182177_RuntimeObject_IntPtr_t(void (*)(), MethodInfo const*, void*, void**) Runtime.cpp - Line 521 il2cpp::vm::Runtime::Invoke(MethodInfo const*, void*, void**, Il2CppException**) ScriptingApi_Il2Cpp.cpp - Line 245 scripting_method_invoke(ScriptingMethodPtr, ScriptingObjectPtr, ScriptingArguments&, ScriptingExceptionPtr*, bool) ScriptingInvocation.cpp - Line 341 ScriptingInvocation::Invoke(ScriptingExceptionPtr*, bool) ScriptingInvocation.h - Line 71 Coroutine::InvokeMoveNext(ScriptingExceptionPtr*) Coroutine.cpp - Line 257 Coroutine::Run(bool*) MonoBehaviour.cpp - Line 742 MonoBehaviour::TryCreateAndRunCoroutine(ScriptingObjectPtr, ScriptingMethodPtr, Coroutine**) MonoBehaviour.cpp - Line 760 MonoBehaviour::StartCoroutineManaged2(ScriptingObjectPtr) unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 3882300 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 26739188 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 1768320 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 1768580 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 2599928 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 2602580 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 2037840 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 21782776 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 21782776 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 26101624 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 22342724 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 22341516 unsigned long long flatbuffers::HashFnv1a<unsigned long long>(char const*) + 22339732 Il2CppInvokerTable.cpp - Line 99434 RuntimeInvoker_Void_t1185182177(void (*)(), MethodInfo const*, void*, void**) Runtime.cpp - Line 521 il2cpp::vm::Runtime::Invoke(MethodInfo const*, void*, void**, Il2CppException**) ScriptingApi_Il2Cpp.cpp - Line 245 scripting_method_invoke(ScriptingMethodPtr, ScriptingObjectPtr, ScriptingArguments&, ScriptingExceptionPtr*, bool) ScriptingInvocation.cpp - Line 341 ScriptingInvocation::Invoke(ScriptingExceptionPtr*, bool) MonoBehaviour.cpp - Line 571 MonoBehaviour::CallUpdateMethod(int) Behaviour.cpp - Line 176 void BaseBehaviourManager::CommonUpdate<BehaviourManager>() PlayerLoop.cpp - Line 340 ExecutePlayerLoop(NativePlayerLoopSystem*) PlayerLoop.cpp - Line 357 ExecutePlayerLoop(NativePlayerLoopSystem*) RecursionLimit.h - Line 45 PlayerLoop() LibEntryPoint.mm - Line 299 UnityPlayerLoopImpl(bool) UnityAppController+Rendering.mm - Line 280 UnityRepaint UnityAppController+Rendering.mm - Line 77 -[UnityAppController(Rendering) repaintDisplayLink] QuartzCore CA::Display::DisplayLink::dispatch_items(unsigned long long, unsigned long long, unsigned long long) + 632

And again, a dozen similar ones.

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  • \$\begingroup\$ Have you tested on hardware other than your development platforms? Do you have any info about how the crashing platforms differ from reliable ones? Is it possible for you to upgrade to a more recent Unity release? \$\endgroup\$ Commented Apr 24, 2019 at 17:33
  • \$\begingroup\$ @Pikalek We have plans to eventually update Unity versions, but cannot do so in the immediate future, due to our desire to avoid unnecessary risk immediately after the 1.0 release. As for devices it's occurring on, we are testing on a variety of devices and OS versions, and the crashes occur on pretty much every combination of device and OS version we support, though not consistently (about 1% of sessions). Users are generally able to play the game but apparently crash occasionally where it would previously work fine, and works fine again later. \$\endgroup\$ Commented Apr 24, 2019 at 18:16
  • \$\begingroup\$ Are these bundles that you made in house? \$\endgroup\$ Commented Apr 25, 2019 at 1:34
  • \$\begingroup\$ Indeed they are. Our build process rebuilds them automatically on each build, and uploads them to a CDN if they have changed. It then updates an asset within the game to point to the correct version. \$\endgroup\$ Commented Apr 25, 2019 at 12:40

3 Answers 3

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The first thing to do is try to narrow down why EXC_BAD_ACCESS errors are occurring. A common cause is attempting to access a deallocated object, also known as a dangling pointer error.

You can check for this in XCode by enabling zombie objects. Doing so allows deallocated objects to be kept around as 'zombies' for debugging purposes. Accessing a zombie will still result in a EXC_BAD_ACCESS. However, it will give you more information about what object you were trying to access, which makes debugging easier.

If that doesn't help, the next step is to have Xcode analyze your project. This will generate a list of issues. These are warnings about things that may need attention. One approach is to filter through the issues & their linked code looking for things that seem most relevant to the problem at hand. If time / resources permit it might be better to go through them and address/correct as many as possible.

Note: sometimes the warnings will not be applicable to your particular situation. However, keep in mind that your code is crashing; don't be quick to convince yourself that you are right & the analysis tool is wrong.

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  • \$\begingroup\$ Unfortunately, as I mentioned, we have not been able to get this to happen when testing on our own. These are crashes coming in from the wild. And since this is a Unity-generated project, there are countless warnings, and the code that is crashing is not even IL2CPP code. It's all internal to Unity's process as far as we can tell (since it's crashing on the UnityPreload thread, not the main Unity thread). \$\endgroup\$ Commented Apr 25, 2019 at 20:11
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I would recommend running with Address Sanitizer. In Xcode's scheme settings for your app, select the "Run" tab on the left, then the "Diagnostics" tab on the top. The first checkbox is "Address Sanitizer." (If it's grayed out, turn off "Malloc Guard Edges" or other settings in that group.) Check the box for Address Sanitizer and check the box for "Detect use Of stack after return". Rebuild, and run. Do whatever it is that triggers serialization. Address Sanitizer will likely stop your application and point out any address misuse you have. It's possible that even though it's not crashing on your system, you may still trigger Address Sanitizer when you read or write past the end of an array, or something similar.

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Turned out this was a Unity bug that they have fixed in the latest Unity update.

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