[ndiddy]

Has any progress been made on this? I remember seeing this proposal 3 or 4 years ago but it looks like it still hasn't been implemented. It's a shame because it seems like a useful feature. It looks like Microsoft has something similar (https://learn.microsoft.com/en-us/cpp/code-quality/understan...) but it would be nice to have something that worked on other platforms.

[Someone]

https://discourse.llvm.org/t/the-preview-of-fbounds-safety-i...:

“-fbounds-safety is a language extension to enforce a strong bounds safety guarantee for C. Here is our original RFC.

We are thrilled to announce that the preview implementation of -fbounds-safety is publicly available at this fork of llvm-project. Please note that we are still actively working on incrementally open-sourcing this feature in the llvm.org/llvm-project . To date, we have landed only a small subset of our implementation, and the feature is not yet available for use there. However, the preview does contain the working feature. Here is a quick instruction on how to adopt it.”

“This fork” is https://github.com/swiftlang/llvm-project/tree/stable/202407..., Apple’s fork of LLVM. That branch is from a year ago.

I don’t know whether there’s a newer publicly available version.

There is a GSoC 2026 opportunity on upstreaming this into mainline LLVM (https://discourse.llvm.org/t/gsoc-2026-participating-in-upst...)

[mrpippy]

Apple is shipping code built with this, and is supporting it for developers to use (see https://developer.apple.com/documentation/xcode/enabling-enh...)

[groos]

Microsoft's SAL annotations are meant to inform the static analyzer how the parameters are meant to be used so any violations of the contract can be diagnosed at compile time. The LLVM proposal is different in that it is checked at run time and will stop your program before it makes an out of bounds access. Static analyzers can obviously use the information in the type to help diagnose a subset of such problems at compile time.

[musicale]

As I and others noted below, it is included in Apple's clang version, which is what you get when you install the command line tools for Xcode. Try something like:

    clang -g -Xclang -fbounds-safety program.c

Bounds check failures result in traps; in lldb you get a message like:

    stop reason = Bounds check failed: Dereferencing above bounds