[llvm-dev] How to debug .ll file with segmentation fault?

[Chandler Carruth via llvm-dev]

Also, there is an entire document on debugging JIT-ed code that is likely
useful: https://llvm.org/docs/DebuggingJITedCode.html

On Fri, Jan 25, 2019 at 11:19 PM mayuyu.io <admin at mayuyu.io> wrote:

> I suggest you try to AOT compile the IR and debug it in the same way as
> you would with native code.
>
> Zhang
>
> 在 2019年1月26日，07:05，Peng Yu via llvm-dev <llvm-dev at lists.llvm.org> 写道：
>
> Could you give specific pointers to the resources that are relevant to
> segmentation fault debugging? This kind of bug is the hardest to bebug
> because the error message has nothing to do with the actual bug.
>
> Generic advices without consideration of specific properties of the
> problem will surely end up inefficient debugging.
>
> What I added to the .ll file in this case are just function calls to write
> something to a file without touching any thing else in the original .ll. I
> can not envision how such changes can cause segmentation faults.
>
> How can even be sure the bug is in the .ll code but not in lli?
>
> Also, in this case, I don’t think running lli through lldb or gdb can be
> helpful, as it will show information of lli not the bitcode converted from
> the edited .ll file.
>
> On Fri, Jan 25, 2019 at 11:44 PM Chandler Carruth <chandlerc at gmail.com>
> wrote:
>
>> Hey Peng,
>>
>> I'm really excited that you're working with LLVM, but I don't think this
>> list is really the best place to get help with the basics of debugging. I'm
>> afraid you'll need to debug this (and learn how to debug this) kind of
>> failure yourself. There are lots of documents and even some good books
>> about this you can find with a quick search.
>>
>>  If you get to the point where there is clearly a bug in LLVM upstream,
>> you can file it on our bug tracker of course.
>>
>> -Chandler
>>
>>
>> On Fri, Jan 25, 2019 at 6:50 PM Peng Yu via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Hi,
>>>
>>> I edited a working .ll file and llvm-as it to a .bc file. But it
>>> causes segmentation fault. I don't know how to debug such errors.
>>> Could anybody show me the best way to debug such errors? Thanks.
>>>
>>> $ TRACE_OUTFILE=/tmp/trace.txt lli /tmp/y/bash_trcr.bc --norc
>>> __trace_init
>>> LLVMSymbolizer: error reading file: No such file or directory
>>> #0 0x00007f162b1ee0ea llvm::sys::PrintStackTrace(llvm::raw_ostream&)
>>> (/usr/lib/llvm-6.0/bin/../lib/libLLVM-6.0.so.1+0x81e0ea)
>>> #1 0x00007f162b1ec366 llvm::sys::RunSignalHandlers()
>>> (/usr/lib/llvm-6.0/bin/../lib/libLLVM-6.0.so.1+0x81c366)
>>> #2 0x00007f162b1ec49b
>>> (/usr/lib/llvm-6.0/bin/../lib/libLLVM-6.0.so.1+0x81c49b)
>>> #3 0x00007f162a7c3890 __restore_rt
>>> (/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
>>> #4 0x00007f162a0923cc _IO_vfprintf
>>> /build/glibc-OTsEL5/glibc-2.27/stdio-common/vfprintf.c:1283:0
>>> #5 0x00007f162a09be54 _IO_fprintf
>>> /build/glibc-OTsEL5/glibc-2.27/stdio-common/fprintf.c:36:0
>>> #6 0x00007f1628ff648e
>>> #7 0x00007f1628e37bc0
>>> #8 0x00007f1628ff63a4
>>> #9 0x00007f1628fc89e5
>>> #10 0x00007f162c3cd79d llvm::MCJIT::runFunction(llvm::Function*,
>>> llvm::ArrayRef<llvm::GenericValue>)
>>> (/usr/lib/llvm-6.0/bin/../lib/libLLVM-6.0.so.1+0x19fd79d)
>>> #11 0x00007f162c3a67f7
>>> llvm::ExecutionEngine::runFunctionAsMain(llvm::Function*,
>>> std::vector<std::__cxx11::basic_string<char, std::char_traits<char>,
>>> std::allocator<char> >,
>>> std::allocator<std::__cxx11::basic_string<char,
>>> std::char_traits<char>, std::allocator<char> > > > const&, char const*
>>> const*) (/usr/lib/llvm-6.0/bin/../lib/libLLVM-6.0.so.1+0x19d67f7)
>>> #12 0x0000563cd2ca472b (lli+0x2772b)
>>> #13 0x00007f162a058b97 __libc_start_main
>>> /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0
>>> #14 0x0000563cd2cad34a (lli+0x3034a)
>>> Stack dump:
>>> 0.    Program arguments: lli /tmp/y/bash_trcr.bc --norc
>>> Segmentation fault
>>>
>>> --
>>> Regards,
>>> Peng
>>>
>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>> --
> Regards,
> Peng
>
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