[LLVMdev] MCJIT and DWARF debugging info and lldb
Christian Schafmeister
chris.schaf at verizon.net
Tue Oct 15 15:33:11 PDT 2013
Andy,
Thank you for following up. I'm developing this to run on Linux in
parallel so at least I could debug there. I'm also glad that I left my
home-brew debugging callbacks in my generated code - that will always
work although it's much heavier-weight than DWARF.
I would love to test any code that you have that supports LLDB debugging
of MCJIT DWARF debug info.
Perhaps I could help get MCJIT debugging working on MachO - although I
don't have a clue how to go about it. Maybe we could chat on #llvm and
we could evaluate if there is any chance I could help with this or if we
should wait until someone more versed in MachO steps up.
"Kaylor, Andrew" <andrew.kaylor at intel.com> writes:
> MCJIT attempts to register DWARF debugging information with ELF
> objects, but I don't believe it does so with MachO. This is a
> historical artifact due to the fact that those of us who worked on the
> ELF part of this didn't know how to do the same thing with MachO.
> Notably, to get it to work correctly RuntimeDyldELF updates some
> headers to point to the live code before it is registered.
>
> We have a working implementation of the Linux version of LLDB supporting MCJIT debugging, but I'm not sure it has been committed to trunk.
>
> It would require some effort to get this working with MachO objects,
> but I don't think it would be a huge effort for someone who knows the
> MachO format well.
>
> -Andy
>
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Christian Schafmeister
> Sent: Tuesday, October 15, 2013 10:27 AM
> To: llvmdev at cs.uiuc.edu
> Subject: [LLVMdev] MCJIT and DWARF debugging info and lldb
>
>
> Hey folks, I've written a Common Lisp compiler using LLVM as the back
> end. I switched to MCJIT a couple of days ago. I generate DWARF
> debugging information for each Compile Unit, Function, LexicalBlock
> and line numbers (using DIBuilder). (I'm on OS X 10.8.5; XCode 5.0;
> ToT LLVM/Clang build rev 192521)
>
> When I check my backtraces in lldb (stock lldb from Xcode 5.0) I don't
> see my DWARF debugging info as I expected - should I be? What is the
> status of DWARF debugging with MCJIT?
>
> Here's an example where I define three functions A, B, and C where A
> generates a backtrace (using backtrace(3) and backtrace_symbols(3))
> and B calls A and C calls B.
>
> The backtrace entries at 6, 10, 14 are my functions a, b, and c.
> All there is is entries like: "??? <white-space> 0x00000001097ee44b 0x0 + 4454278219"
>
>
>> (defun a () (core::backtrace))
> A
>> (defun b () (a))
> B
>> (defun c () (b))
> C
>> (c)
> (c)
>
>
> Backtrace: 0 libcore_opt.dylib 0x0000000103a61687 _ZN4core12af_backtraceEv + 55
> Backtrace: 1 libcore_opt.dylib 0x0000000103a62c50
>> _ZN4core27ActivationFrameFunctionPtrTIvvvvvvvvvvvvvvvvvE8activateEPFvvERKN3mem9smart_ptrINS_17ActivationFrame_OEEE
>> + 64
> Backtrace: 2 libcore_opt.dylib 0x0000000103a62b12
>> _ZN4core30ActivationFrameFunctionWrapPtrIvvvvvvvvvvvvvvvvvE8activateERKN3mem9smart_ptrINS_17ActivationFrame_OEEE
>> + 18
> Backtrace: 3 libcore_opt.dylib 0x0000000103c8c3c1 _ZN4core9BuiltIn_O6INVOKEERKN3mem9smart_ptrINS_17ActivationFrame_OEEE + 1137
> Backtrace: 4 libllvmo_opt.dylib 0x000000010364758c
>> _Z47proto_invokePossibleMultipleValueSymbolFunctionPN3mem9smart_ptrIN4core8Symbol_OEEEPNS0_INS1_17ActivationFrame_OEEE
>> + 1196
> Backtrace: 5 libllvmo_opt.dylib 0x000000010363ffa7 mv_invokePossibleMultipleValueSymbolFunction + 23
> Backtrace: 6 ??? 0x00000001097ee44b 0x0 + 4454278219
> Backtrace: 7 libcore_opt.dylib 0x0000000103c8d50f
>> _ZN4core18CompiledFunction_O6INVOKEERKN3mem9smart_ptrINS_17ActivationFrame_OEEE
>> + 463
> Backtrace: 8 libllvmo_opt.dylib 0x000000010364758c
>> _Z47proto_invokePossibleMultipleValueSymbolFunctionPN3mem9smart_ptrIN4core8Symbol_OEEEPNS0_INS1_17ActivationFrame_OEEE
>> + 1196
> Backtrace: 9 libllvmo_opt.dylib 0x000000010363ffa7 mv_invokePossibleMultipleValueSymbolFunction + 23
> Backtrace: 10 ??? 0x00000001097f244b 0x0 + 4454294603
> Backtrace: 11 libcore_opt.dylib 0x0000000103c8d50f
>> _ZN4core18CompiledFunction_O6INVOKEERKN3mem9smart_ptrINS_17ActivationFrame_OEEE
>> + 463
> Backtrace: 12 libllvmo_opt.dylib 0x000000010364758c
>> _Z47proto_invokePossibleMultipleValueSymbolFunctionPN3mem9smart_ptrIN4core8Symbol_OEEEPNS0_INS1_17ActivationFrame_OEEE
>> + 1196
> Backtrace: 13 libllvmo_opt.dylib 0x000000010363ffa7 mv_invokePossibleMultipleValueSymbolFunction + 23
> Backtrace: 14 ??? 0x00000001097f444b 0x0 + 4454302795
> Backtrace: 15 libcore_opt.dylib 0x0000000103c8d50f
>> _ZN4core18CompiledFunction_O6INVOKEERKN3mem9smart_ptrINS_17ActivationFrame_OEEE
>> + 463
> Backtrace: 16 libllvmo_opt.dylib 0x000000010364758c
>> _Z47proto_invokePossibleMultipleValueSymbolFunctionPN3mem9smart_ptrIN4core8Symbol_OEEEPNS0_INS1_17ActivationFrame_OEEE
>> + 1196
> Backtrace: 17 libllvmo_opt.dylib 0x000000010363ffa7 mv_invokePossibleMultipleValueSymbolFunction + 23
> Backtrace: 18 ??? 0x00000001097f611c 0x0 + 4454310172
> Backtrace: 19 libcore_opt.dylib 0x0000000103c8d50f
>> _ZN4core18CompiledFunction_O6INVOKEERKN3mem9smart_ptrINS_17ActivationFrame_OEEE
>> + 463
> Backtrace: 20 libcore_opt.dylib 0x0000000103df6397
>> _ZN4core4eval30applyFunctionToActivationFrameEN3mem9smart_ptrINS_10Function_OEEERKNS2_INS_17ActivationFrame_OEEE
>> + 103
> Backtrace: 21 libcore_opt.dylib 0x0000000103dd06c3 _ZN4core4eval5applyEN3mem9smart_ptrINS_3T_OEEERKNS2_INS_17ActivationFrame_OEEE + 483
> Backtrace: 22 libcore_opt.dylib 0x0000000103dcf33f
>> _ZN4core14af_evalWithEnvEN3mem9smart_ptrINS_3T_OEEENS1_INS_13Environment_OEEEbbb
>> + 1055
> Backtrace: 23 libcore_opt.dylib 0x0000000103e0512f
>> _ZN4core27ActivationFrameFunctionPtrTIN3mem15multiple_valuesINS_3T_OEEENS1_9smart_ptrIS3_EENS5_INS_13Environment_OEEEbbbvvvvvvvvvvvE8activateEPFS4_S6_S8_bbbERKNS5_INS_17ActivationFrame_OEEE
>> + 655
> Backtrace: 24 libcore_opt.dylib 0x0000000103e04e42
>> _ZN4core30ActivationFrameFunctionWrapPtrIN3mem15multiple_valuesINS_3T_OEEENS1_9smart_ptrIS3_EENS5_INS_13Environment_OEEEbbbvvvvvvvvvvvE8activateERKNS5_INS_17ActivationFrame_OEEE
>> + 18
> Backtrace: 25 libcore_opt.dylib 0x0000000103c8c3c1 _ZN4core9BuiltIn_O6INVOKEERKN3mem9smart_ptrINS_17ActivationFrame_OEEE + 1137
> Backtrace: 26 libllvmo_opt.dylib 0x000000010364758c
>> _Z47proto_invokePossibleMultipleValueSymbolFunctionPN3mem9smart_ptrIN4core8Symbol_OEEEPNS0_INS1_17ActivationFrame_OEEE
>> + 1196
> Backtrace: 27 libllvmo_opt.dylib 0x000000010363ffa7 mv_invokePossibleMultipleValueSymbolFunction + 23
> Backtrace: 28 _image.bundle 0x000000010b5771c8 REP + 1816
> Backtrace: 29 ??? 0x000000010d71dd50 0x0 + 4520533328
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
More information about the llvm-dev
mailing list