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Put noundef on all scalars that don't allow uninit #106294

Merged
merged 3 commits into from
Jan 17, 2023
Merged

Put noundef on all scalars that don't allow uninit #106294

merged 3 commits into from
Jan 17, 2023

Commits on Jan 17, 2023

  1. Put noundef on all scalars that don't allow uninit 

    Previously, it was only put on scalars with range validity invariants
like bool, was uninit was obviously invalid for those.

Since then, we have normatively declared all uninit primitives to be
undefined behavior and can therefore put `noundef` on them.

The remaining concern was the `mem::uninitialized` function, which cause
quite a lot of UB in the older parts of the ecosystem. This function now
doesn't return uninit values anymore, making users of it safe from this
change.

The only real sources of UB where people could encounter uninit
primitives are `MaybeUninit::uninit().assume_init()`, which has always
be clear in the docs about being UB and from heap allocations (like
reading from the spare capacity of a vec. This is hopefully rare enough
to not break anything.
    @Noratrieb
    Noratrieb committed Jan 17, 2023
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  2. Improve comments

    @Noratrieb
    Noratrieb committed Jan 17, 2023
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  3. Add more codegen tests

    @Noratrieb
    Noratrieb committed Jan 17, 2023
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