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

[preejackie via llvm-dev]

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

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 <mailto: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;
>     autoRM =Optional<Reloc::Model>();
>     autoTheTargetMachine =
>     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 <mailto:llvm-dev at lists.llvm.org>
>     https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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