[NSan] How to enable Numerical Sanitizer in Clang++ and generate instrumented code?

[bartlettroscoe]

CC: @alexander-shaposhnikov, @firewave, @cjappl

I know this is closely related to:

• NumericalStabilitySanitizer lacks documentation #98869

but how to you enable support for the Numerical Sanitizer (NSan) described in the paper:

• “NSan: A Floating-Point Numerical Sanitizer” https://arxiv.org/pdf/2102.12782 (paper from 2021)

?

Is this as simple as setting a compiler option or do you need to build a version of LLVM Clang++ that even has support for NSan?

I can likely dig through source code and other places to figure this out, but I thought I might just ask.

[firewave]

-fsanitize=numerical

[bartlettroscoe]

-fsanitize=numerical

And the default LLVM clang++ compiler is built by default to support this option? (Or it will in LLVM 20.0 release?)

[firewave]

It is supported by Clang 19+ and should be built-in by default.

[llvmbot]

@llvm/issue-subscribers-clang-driver

Author: Roscoe A. Bartlett (bartlettroscoe)

CC: @alexander-shaposhnikov, @firewave, @cjappl

I know this is closely related to:

• #98869

but how to you enable support for the Numerical Sanitizer (NSan) described in the paper:

• “NSan: A Floating-Point Numerical Sanitizer” https://arxiv.org/pdf/2102.12782 (paper from 2021)

?

Is this as simple as setting a compiler option or do you need to build a version of LLVM Clang++ that even has support for NSan?

I can likely dig through source code and other places to figure this out, but I thought I might just ask.

[bartlettroscoe]

Thanks for answering questions! I will work on building LLVM Clang++ 19.1.z and testing this out.

Closing this issue.

[bartlettroscoe]

FYI: I was able to build and install 'main' version of LLVM and verify that just setting the compiler option -fsanitize=numerical enabled NSan and produced some errors.