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libc++experimental built w/ UBSAN has undefined references to __muloti4 builtin #29991

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llvmbot opened this issue Oct 8, 2016 · 2 comments
Open

libc++experimental built w/ UBSAN has undefined references to __muloti4 builtin #29991

llvmbot opened this issue Oct 8, 2016 · 2 comments
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bugzilla Issues migrated from bugzilla libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi.

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@llvmbot
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llvmbot commented Oct 8, 2016

Bugzilla Link 30643
Version unspecified
OS Windows NT
Reporter LLVM Bugzilla Contributor
CC @apolukhin,@mclow

Extended Description

For some reason the typical GNU libraries don't provide this builtin, but libclang_rt.builtins-x86_64.a does. This means that the user must manually link the libclang builtins to get UBSAN to work.

The missing builtin is required when doing 128-bit integer multiplication in filesystem.

I'm filing this bug as a reminder to fix this.
@llvmbot
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llvmbot commented Oct 10, 2016

I removed usages of __int128_t in r283712, which fixes this bug.

@llvmbot
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llvmbot commented Jul 25, 2018

We once again use __int128_t in filesystem, so this bug has cropped up again.

I think as a temporary fix, libc++ can crib the mul0ti4 implementation from compiler-rt and compile it into filesystem manually.

I'll look into more involved fixes as well.

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 10, 2021
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bugzilla Issues migrated from bugzilla libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi.
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