offset_of! not stable in Rust v1.63.0

[marcpabst]

Bug Description

I think #4254 introduced usage of the offset_of! macro which is not available in the current MSRV.

Steps to Reproduce

Build with v1.63.0

Backtrace

No response

Your operating system and version

n/a

Your Python version (python --version)

n/a

Your Rust version (rustc --version)

< 1.77.0

Your PyO3 version

0.22.2

How did you install python? Did you use a virtualenv?

n/a

Additional Info

No response

[alex]

This only uses the offset of macro from the memoffset crate as far as I can tell.

…

On Thu, Aug 1, 2024, 3:20 PM Marc Pabst ***@***.***> wrote: Bug Description I think #4254 <#4254> introduced usage of the offset_of! macro which is not available in the current MSRV. Steps to Reproduce Build with v1.63.0 Backtrace *No response* Your operating system and version n/a Your Python version (python --version) n/a Your Rust version (rustc --version) < 1.77.0 Your PyO3 version 0.22.2 How did you install python? Did you use a virtualenv? n/a Additional Info *No response* — Reply to this email directly, view it on GitHub <#4408>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAAGBDLWCO3EO2P6DD2653ZPKC6FAVCNFSM6AAAAABL3FW6ZOVHI2DSMVQWIX3LMV43ASLTON2WKOZSGQ2DGMRTGA2DMNQ> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[marcpabst]

I'm seing a error[E0658]: use of unstable library feature 'offset_of':

error[E0658]: use of unstable library feature 'offset_of'
   --> /Users/marc/.cargo/registry/src/index.crates.io-6f17d22bba15001f/pyo3-0.21.0/src/types/capsule.rs:143:26
    |
143 |         debug_assert_eq!(memoffset::offset_of!(CapsuleContents::<T, F>, value), 0);
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #106655 <https://github.com/rust-lang/rust/issues/106655> for more information
    = help: add `#![feature(offset_of)]` to the crate attributes to enable
    = note: this error originates in the macro `_memoffset__offset_of_impl` which comes from the expansion of the macro `memoffset::offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)

[davidhewitt]

Try running cargo update; looks like a possible memoffset issue from an older version maybe.

Also your error is from a PyO3 0.21 source file so predates #4254

[marcpabst]

Yeah, looks like it's my messed-up local toolchain which reports as a newer version than what it actually is. I suspect that in turn confuses memoffset - so not actually a Pyo3 issue. Sorry!