Re: [PATCH v3 0/3] Detect changed compiler dependencies for full rebuild

Nicolas Schier
2025-05-07T12:02:54Z

On Sat, 03 May 2025, Kees Cook wrote:

> v3: move to include/generated, add touch helper
> v2: https://lore.kernel.org/lkml/20250502224512.it.706-kees@kernel.org/
> v1: https://lore.kernel.org/lkml/20250501193839.work.525-kees@kernel.org/
>
> Hi,
>
> This is my attempt to introduce dependencies that track the various
> compiler behaviors that may globally change the build that aren't
> represented by either compiler flags nor the compiler version
> (CC_VERSION_TEXT). Namely, this is to detect when the contents of a
> file the compiler uses changes. We have 3 such situations currently in
> the tree:
>
> - If any of the GCC plugins change, we need to rebuild everything that
> was built with them, as they may have changed their behavior and those
> behaviors may need to be synchronized across all translation units.
> (The most obvious of these is the randstruct GCC plugin, but is true
> for most of them.)
>
> - If the randstruct seed itself changes (whether for GCC plugins or
> Clang), the entire tree needs to be rebuilt since the randomization of
> structures may change between compilation units if not.
>
> - If the integer-wrap-ignore.scl file for Clang's integer wrapping
> sanitizer changes, a full rebuild is needed as the coverage for wrapping
> types may have changed, once again cause behavior differences between
> compilation units.

I am unsure if it is too much detail, but I'd like to see some of these
infos in include/linux/compiler-version.h, too.

Kind regards,
Nicolas