Gcc already has [[gnu::uninitialized]] (clang doesn't, AFAIK), as well as -ftrivial-auto-var-init=pattern which exactly matches the new C++26 semantics, if I'm not mistaken
> -ftrivial-auto-var-init=pattern
I believe this only helps for trivial automatic variables; not non-trivial automatic variables (structs/classes) that contain uninitialized trivial members.