LLVM Kaleidoscope : Compiling to Object Code - Segmentation Fault

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#1

Hi all :slight_smile:

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 = OptionalReloc::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 :slight_smile:

Thanks for your kind help

#2

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

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?

#3

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.


``

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
#4

Still haven’t had much luck reproducing this

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.


``

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?

#5

Hi David