UBSAN failures in clang constant interpreter tests on 32 bit ARM #94741
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To reproduce by cross compiling on Linux: Download toolchain from: https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads Extract and add it to your PATH: Set up a symlink inside the toolchain so it can find Then configure llvm using this script:
Now install Interestingly, these values are different from what we see on armv8 hardware, which makes sense if there is UB here. To reproduce the other failed tests, add I will continue to look for a solution on native hardware. |
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Currently suspect this code: |
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Hey I just wanna point out |
DavidSpickett
changed the title
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Thank you, I had confused the two. Which means the issue caused by #89811 is in clang-repl and the ones I'm seeing here are in the constant interpreter. |
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For those who have access to hardware, I could use the rest of the cross compilation guide for running on Raspberry Pi 4, Debian 12. I have used GCC 12.2 for glibc compatibility, instead of GCC 13.2
GCC 12.2 available here: https://developer.arm.com/-/media/Files/downloads/gnu/12.2.rel1/binrel/arm-gnu-toolchain-12.2.rel1-x86_64-arm-none-linux-gnueabihf.tar.xz?rev=9929cb6c0e8948f0ba1a621167fcd56d&hash=8F13B510F8B20149258CB4AA5372BF92 |
frederick-vs-ja
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clang:frontend
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@llvm/issue-subscribers-clang-frontend Author: David Spickett (DavidSpickett)
Doing a 32 bit Arm build with UBSAN enabled, I get many failures from the clang interpreter:
```
Clang :: AST/Interp/arrays.cpp
Clang :: AST/Interp/atomic.c
Clang :: AST/Interp/atomic.cpp
Clang :: AST/Interp/bitfields.cpp
Clang :: AST/Interp/builtin-align-cxx.cpp
Clang :: AST/Interp/builtin-functions.cpp
Clang :: AST/Interp/builtins.cpp
Clang :: AST/Interp/c.c
Clang :: AST/Interp/c23.c
Clang :: AST/Interp/comma.cpp
Clang :: AST/Interp/complex.c
Clang :: AST/Interp/complex.cpp
Clang :: AST/Interp/cond.cpp
Clang :: AST/Interp/const-eval.c
Clang :: AST/Interp/const-fpfeatures.cpp
Clang :: AST/Interp/constexpr-nqueens.cpp
Clang :: AST/Interp/constexpr-subobj-initialization.cpp
Clang :: AST/Interp/cxx03.cpp
Clang :: AST/Interp/cxx11.cpp
Clang :: AST/Interp/cxx17.cpp
Clang :: AST/Interp/cxx20.cpp
Clang :: AST/Interp/cxx23.cpp
Clang :: AST/Interp/cxx98.cpp
Clang :: AST/Interp/depth-limit.cpp
Clang :: AST/Interp/enums-targets.cpp
Clang :: AST/Interp/enums.cpp
Clang :: AST/Interp/eval-order.cpp
Clang :: AST/Interp/floats.cpp
Clang :: AST/Interp/functions.cpp
Clang :: AST/Interp/if.cpp
Clang :: AST/Interp/intap.cpp
Clang :: AST/Interp/invalid.cpp
Clang :: AST/Interp/lambda.cpp
Clang :: AST/Interp/lifetimes.cpp
Clang :: AST/Interp/literals.cpp
Clang :: AST/Interp/loops.cpp
Clang :: AST/Interp/memberpointers.cpp
Clang :: AST/Interp/nullable.cpp
Clang :: AST/Interp/objc.mm
Clang :: AST/Interp/opencl.cl
Clang :: AST/Interp/pointer-addition.c
Clang :: AST/Interp/records.cpp
Clang :: AST/Interp/references.cpp
Clang :: AST/Interp/shifts.cpp
Clang :: AST/Interp/spaceship.cpp
Clang :: AST/Interp/switch.cpp
Clang :: AST/Interp/sycl.cpp
Clang :: AST/Interp/unions.cpp
Clang :: AST/Interp/vectors.cpp
Clang :: AST/Interp/weak.cpp
```
Most of them are problems with reference binding or calling of constructors on misaligned addresses. Usually the type requires 8 byte alignment but the address is 4 byte aligned.
I think the assumptions in the interpreter's management of its virtual stack do not hold for 32 bit Arm. I don't know that that's the cause of all the issues we have seen without UBSAN, but it seems likely. |
Doing a 32 bit Arm build with UBSAN enabled, I get many failures from the clang interpreter:
Most of them are problems with reference binding or calling of constructors on misaligned addresses. Usually the type requires 8 byte alignment but the address is 4 byte aligned.
This has come up a lot recently, including #89811 which has "uncovered" this issue outside of UBSAN builds.I think the assumptions in the interpreter's management of its virtual stack do not hold for 32 bit Arm. I don't know that that's the cause of all the issues we have seen without UBSAN, but it seems likely.
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