[llvm-dev] A stage2 build causes changes to libllvm impacting program using it (exemple: rustc)

[Philip Pfaffe via llvm-dev]

Hi Sylvestre,

isn't this another instance of the clang-7/gcc ABI issue around Optional?

llvm::DIBuilder::createFile accepts Optional arguments, and more than once
people complained to me or on IRC about that particular call segfaulting.

Cheers,
Philip

On Sun, Nov 11, 2018 at 9:54 AM Sylvestre Ledru via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hello,
>
> Lately, I have been working on moving Debian & Ubuntu packages to a
> stage2 build.
>
> This means that, instead of shipping llvm-toolchain packages built with
> gcc, we are rebuilding
> everything a second time using the newly built clang.
>
> Now, when pushed to Debian, it caused some unexpected issues in
> particular with rust reported here:
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=913271#35
>
> rustc in Debian was building initially against libllvm built with gcc.
> It was working fine.
> The failure is now happening when the systems saw their libllvm upgraded
> to the stage2 bootstrap one.
>
> The beginning of the backtrace is the following (generating debug info):
>
> Thread 1 "rustc" received signal SIGSEGV, Segmentation fault.
> 0x00007ffff1e273bc in
> llvm::StringMapImpl::LookupBucketFor(llvm::StringRef) () from
> /usr/lib/x86_64-linux-gnu/libLLVM-7.so.1
> (gdb) bt
> #0  0x00007ffff1e273bc in
> llvm::StringMapImpl::LookupBucketFor(llvm::StringRef) () from
> /usr/lib/x86_64-linux-gnu/libLLVM-7.so.1
> #1  0x00007ffff1f654c9 in ?? () from
> /usr/lib/x86_64-linux-gnu/libLLVM-7.so.1
> #2  0x00007ffff1f65491 in llvm::MDString::get(llvm::LLVMContext&,
> llvm::StringRef) () from /usr/lib/x86_64-linux-gnu/libLLVM-7.so.1
> #3  0x00007ffff1ee69cd in ?? () from
> /usr/lib/x86_64-linux-gnu/libLLVM-7.so.1
> #4  0x00007ffff1ee2d12 in llvm::DIBuilder::createFile(llvm::StringRef,
> llvm::StringRef, llvm::Optional<llvm::DIFile::ChecksumInfo<llvm::StringRef>
> >, llvm::Optional<llvm::StringRef>) () from
> /usr/lib/x86_64-linux-gnu/libLLVM-7.so.1
> #5  0x00007ffff50a01f2 in LLVMRustDIBuilderCreateFile
> (Builder=0x5555555d4180, Filename=0x7ffffffeedd8 "src/main.rs",
> Directory=0x555555b3dd10 "$HOME/hello_world")
>     at /usr/lib/llvm-7/include/llvm/ADT/StringRef.h:85
> #6  0x00007ffff501d39e in
> rustc_codegen_llvm::debuginfo::metadata::compile_unit_metadata (tcx=...,
> codegen_unit_name=..., debug_context=0x7ffffffeeeb0) at
> librustc_codegen_llvm/debuginfo/metadata.rs:859
>
> Disabling the debug generation for rustc fixes the issue (thanks to Ximin
> Luo for the investigation).
>
> Why idea how to workaround this issue ?
>
> Unfortunately, because rustc needs rustc to build itself, I cannot check
> if a simple recompilation fixes it or not.
>
> Cheers,
> S
>
>
> _______________________________________________
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> llvm-dev at lists.llvm.org
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