ASAN reports out-of-bounds read error in `anderson2021_test_apps_autoscheduler`

[steven-johnson]

ASAN is reporting an out-of-bounds read error in SearchSpace.cpp:125; examination reveals that we are reading past the end of a std::vector (in this case, c->size.size() is 1, but l.pure_dim is 1)... so this is a real bug.

Unfortunately I have no idea where to even begin debugging this... assigning to @abadams for now to see if he can route it to the right person.

(ASAN isn't necessary to repro this bug, just add something like internal_assert(l.pure_dim < c->size.size()); in the code)

(But if you want to run with asan, just add --preset linux-x64-asan to the cmake and ctest commands)

[abadams]

Ideally @aekul could take a look.

[Yongqi-Zhuo]

Any updates on this? :)
Looking forward to using this in production

[aekul]

Will take a look at this in the next few days.

[aekul]

I'm not able to reproduce this. I added an assert and built Halide with CMake but things work fine. Is that all I should have to do to reproduce it? @steven-johnson or @Yongqi-Zhuo are using the default settings for the autoscheduler?

[steven-johnson]

You need to run with ASAN (Address Sanitizer) to repro. Specify --preset linux-x64-asan as mentioned above.

[aekul]

I'm having trouble getting ASAN to build. I've tried LLVM 15 and 16, but can't build either of them. Error is:

CMake Error at cmake/Modules/CompilerRTUtils.cmake:434 (string):
  string sub-command REPLACE requires at least four arguments.
Call Stack (most recent call first):
  CMakeLists.txt:118 (construct_compiler_rt_default_triple)

Tried Googling but can't find any way to resolve it. "compiler-rt" seems to be the issue. Is -DLLVM_ENABLE_RUNTIMES="compiler-rt" required for ASAN?

[steven-johnson]

Yikes, yes, sorry (I thought this was in the readme)... for ASAN you must build LLVM with

-D LLVM_ENABLE_PROJECTS="clang;lld;clang-tools-extra" 
-D LLVM_ENABLE_RUNTIMES="compiler-rt;libcxx;libcxxabi;libunwind" 

(I have only tested recently with top-of-tree LLVM but 16 should work)

[aekul]

Building LLVM works with those changes, thanks. But now when I compile Halide, I get Float16.h:43:24: error: _Float16 is not supported on this target when using --preset linux-x64-asan or --preset release. Any ideas? I'm using a PowerPC machine in case that's relevant.

[steven-johnson]

As you may surmise from the name, the linux-x64-asan preset has only been designed/tested for use on x86-64 Linux machines, so this failure isn't surprising.

(Frankly, though, I'm surprised that the Float16 stuff isn't failing for you on PowerPC in general, since that support is fairly specific to x86 / ARM IIUC, and we do basically zero testing of our PowerPC backend at this point.)

[antonysigma]

@steven-johnson @aekul Here you are, the minimal repro that triggers the ASAN error with Anderson2021 autoscheduler. #7699

The same code did not trigger ASAN error with the Mullapudi2016 autoscheduler.

I am also open to a code rewrite/refactoring to bypass the ASAN error.