[llvm-dev] LLVM Kaleidoscope : Compiling to Object Code - Segmentation Fault

[David Blaikie via llvm-dev]

Still haven't had much luck reproducing this
On Thu, Jan 24, 2019 at 1:19 PM preejackie <praveenvelliengiri at gmail.com>
wrote:

> Hi David!
>
> Thanks for reaching out, the codegen part of the tutorial is fine, but
> when I try to generate the object code file, it throws segfault. Also
> please note that I'm using release build of llvm, actually I don't know
> whether that is the root cause or not.
>
> I also run through valgrind, it seems like a invalid read from stack.
>
> Error Summary:
>
> 1 errors in context 1 of 1:
> ==4153== Invalid read of size 1
> ==4153==    at 0x4AFEE0:
> llvm::optional_detail::OptionalStorage<llvm::Reloc::Model,
> true>::OptionalStorage(llvm::optional_detail::OptionalStorage<llvm::Reloc::Model,
> true> const&) (in /home/preejackie/kld/toy)
> ==4153==    by 0x4B098D:
> llvm::RegisterTargetMachine<llvm::X86TargetMachine>::Allocator(llvm::Target
> const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef,
> llvm::TargetOptions const&, llvm::Optional<llvm::Reloc::Model>,
> llvm::Optional<llvm::CodeModel::Model>, llvm::CodeGenOpt::Level, bool) (in
> /home/preejackie/kld/toy)
> ==4153==    by 0x46CE5B: createTargetMachine (TargetRegistry.h:397)
> ==4153==    by 0x46CE5B: main (kjit.cpp:1337)
> ==4153==  Address 0x4 is not stack'd, malloc'd or (recently) free'd
>
> Source compile command : clang++ -g -O3 kjit.cpp `llvm-config --cxxflags
> --ldflags --system-libs --libs all` -o toy
>
> Please, let me know that if you need some additional information :)
>
> Thanks a lot
>

Oh, hmm, this might be that ABI problem
https://bugs.llvm.org/show_bug.cgi?id=39427 - if the release you're using
was built with GCC and you're building your code with Clang, that could be
it.

Maybe try building with GCC?


> On 25/01/19 1:47 AM, David Blaikie wrote:
>
> Hi there!
>
> Sorry to hear you're having trouble with the examples & thanks for
> reaching out.
>
> I'm having some difficulty reproducing the failure mode you described.
> From the code sample, it sounds like you're in Chapter 8 and I just took a
> look at Chapter 8 in my debug build and got this result:
>
> $ ./bin/Kaleidoscope-Ch8
> ready> def average(x y) (x + y) * 0.5;
> Read function definition:
> define double @average(double %x, double %y) {
> entry:
>   %y2 = alloca double
>   %x1 = alloca double
>   store double %x, double* %x1
>   store double %y, double* %y2
>   %x3 = load double, double* %x1
>   %y4 = load double, double* %y2
>   %addtmp = fadd double %x3, %y4
>   %multmp = fmul double %addtmp, 5.000000e-01
>   ret double %multmp
> }
>
>
> Any  ideas what you might be doing differently that I could do to try to
> reproduce the failure you're seeing?
>
> On Thu, Jan 24, 2019 at 9:36 AM preejackie via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi all :)
>>
>> I'm new to llvm!
>>
>> I'm going through the kaleidoscope : compiling llvm IR to object code
>> tutorial, code in the listings breaks and causes a segmentation fault.
>> After some investigation through gdb, probably this constructor call,
>> causing the segfault.
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x00000000004afee0 in
>> llvm::optional_detail::OptionalStorage<llvm::Reloc::Model,
>> true>::OptionalStorage(llvm::optional_detail::OptionalStorage<llvm::Reloc::Model,
>> true> const&) ()
>>
>> Source code:
>> TargetOptions opt;
>> auto RM = Optional<Reloc::Model>();
>> auto TheTargetMachine =
>> Target->createTargetMachine(TargetTriple, CPU, Features, opt, RM);
>>
>> Whether this behavior is already notified and is there any workaround
>> available for it ? I would be great to know the root cause for this
>> behavior.
>>
>> Of course, the kaleidoscope is friendly and good introduction to llvm for
>> beginners, thank you very much for developing :)
>>
>> Thanks for your kind help
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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