[lldb-dev] Quite annoying assertion

[Enrico Granata]

> 
> I just got it. 
> 
> NSArray *arr = [NSArray array];
> 
> following code will trigger assertion:
> 
> SBValue res = frame.EvaluateExpression("[arr respondsToSelector:@selector(objectEnumerator)]");
> if (res.IsValid()) {
>     res.GetTypeName(); //  <-- here
> }
> 
> backtrace:
> #0  0x00007fff817aa9ce in __semwait_signal_nocancel ()
> #1  0x00007fff817aa8d0 in nanosleep$NOCANCEL ()
> #2  0x00007fff818073ce in usleep$NOCANCEL ()
> #3  0x00007fff81826a00 in abort ()
> #4  0x00007fff818139bc in __assert_rtn ()
> #5  0x00000001002e5f43 in lldb_private::ClangASTType::GetTypeNameForQualType ()
> #6  0x00000001002e60f1 in lldb_private::ClangASTType::GetConstTypeName ()
> #7  0x0000000100259bf9 in lldb_private::ValueObjectConstResult::GetTypeName ()
> #8  0x0000000100189607 in lldb::SBValue::GetTypeName ()
> #9  0x000000010006f29e in jetcidr::EvaluatedValue2LLDBValue (pair=@0x101f86a78, lldb_val=0x1034c5050) at ResponseFactory.h:52
> #10 0x000000010007b7cc in jetcidr::ResponseFactory::EvaluateExpression (this=0x103407910, pair=@0x101f86b20) at /Users/zajac/Projects/ULTIMATE/CIDR/LLDBProtobufFrontend/LLDBProtobufFrontend/src/ResponseFactory.cpp:92
> #11 0x000000010006b8f1 in jetcidr::ProtobufHandler::HandleEvaluateExpression (this=0x1031001d0, req=@0x1034ade10) at /Users/zajac/Projects/ULTIMATE/CIDR/LLDBProtobufFrontend/LLDBProtobufFrontend/src/ProtobufHandler.cpp:156
> #12 0x000000010006c2cf in jetcidr::ProtobufHandler::ProcessMessage (this=0x1031001d0, req=@0x101f86c50) at /Users/zajac/Projects/ULTIMATE/CIDR/LLDBProtobufFrontend/LLDBProtobufFrontend/src/ProtobufHandler.cpp:236
> #13 0x000000010006c620 in __HandleHasBytesAvailable_block_invoke_0 (.block_descriptor=<value temporarily unavailable, due to optimizations>) at /Users/zajac/Projects/ULTIMATE/CIDR/LLDBProtobufFrontend/LLDBProtobufFrontend/src/ProtobufHandler.cpp:261
> #14 0x00007fff8176cfbb in dispatch_barrier_sync_f ()
> #15 0x000000010006c42f in jetcidr::ProtobufHandler::HandleHasBytesAvailable (this=0x1031001d0, r_source=0x103100000) at /Users/zajac/Projects/ULTIMATE/CIDR/LLDBProtobufFrontend/LLDBProtobufFrontend/src/ProtobufHandler.cpp:252
> #16 0x00000001000699b1 in __StartHandlingClient_block_invoke_05 (.block_descriptor=<value temporarily unavailable, due to optimizations>) at /Users/zajac/Projects/ULTIMATE/CIDR/LLDBProtobufFrontend/LLDBProtobufFrontend/src/ProtobufServer.cpp:76
> #17 0x00007fff817533f3 in _dispatch_source_invoke ()
> #18 0x00007fff817527b4 in _dispatch_queue_invoke ()
> #19 0x00007fff817528dc in _dispatch_queue_drain ()
> #20 0x00007fff81752734 in _dispatch_queue_invoke ()
> #21 0x00007fff817522de in _dispatch_worker_thread2 ()
> #22 0x00007fff81751c08 in _pthread_wqthread ()
> #23 0x00007fff81751aa5 in start_wqthread ()
> 
> This happened for me only in 32-bit mode when running app in simulator and attaching to process by pid.

Do you mean you tried all other possible combinations (64-bit, not attaching by PID, ...) and the only way to get the crash is "32-bit in simulator(which simulator? iOS?) attaching by PID"?

If so, trying to reproduce this consistently might take some effort. If, on the other side, this happens in other possible scenarios, I bet it is an incomplete type problem.
Which version of LLDB are you using?

> But(!): 
> 
> (lldb) p [arr respondsToSelector:@selector(objectEnumerator)]
> error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=1, address=0xffffffff).
> The process has been returned to the state before execution.
> 
> After this lldb won't crash.
> 
> What am I doing wrong?
> 

> On 09.08.2011, at 2:38, Enrico Granata wrote:
> 
>> Would you be able to provide example commands that trigger this?
>> This looks like some of your types are not completed, but it's hard to tell which ones and why without something reproducible
>> 
>> On Aug 8, 2011, at 3:34 PM, Andrey Zaytsev wrote:
>> 
>>> Hello everyone!
>>> I'm very often getting this assertion when evaluating some sort of expressions:
>>> 
>>> Assertion failed: (!isNull() && "Cannot retrieve a NULL type pointer"), function getCommonPtr, file /SourceCache/lldb/lldb-69/llvm/tools/clang/include/clang/AST/Type.h, line 404.
>>> 
>>> This assertion fires every time I'm evaluating something like this: "[0x12345.. someSelector]". I'm stuck with it because I need values of this kind of expressions to display ns-collections.
>>> 
>>> Thanks for your consideration.
>>> _______________________________________________
>>> lldb-dev mailing list
>>> lldb-dev at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>> 
>> 
>> Thanks,
>> Enrico Granata
>> ✆ 408.974.5572 | ✉ egranata@.com
>> 
>> 
>> 
>> 
> 
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Enrico Granata
✆ 408.974.5572 | ✉ egranata@.com




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