Tracking issue for proc_macro::is_available() #71436

dtolnay · 2020-04-22T18:06:03Z

This is a tracking issue for proc_macro::is_available().
The feature gate for the issue is #![feature(proc_macro_is_available)].

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also uses as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.

Steps

Implement -- proc_macro::is_available() #71400
Adjust documentation
Stabilization PR (see instructions on rustc-dev-guide) -- Stabilize proc_macro::is_available #89735

Unresolved Questions

none yet

Implementation history

Implemented in proc_macro::is_available() #71400

The text was updated successfully, but these errors were encountered:

Aaron1011 · 2020-06-12T22:07:05Z

Is anything blocking stabilization of this feature? It seems pretty uncontroversial - if the proc_macro crate ever gained the ability to be used outside of a procedural macro, this function could just unconditionally return true.

dtolnay · 2020-06-12T22:45:39Z

One non-uncontroversial part is how to react if proc_macro might not be all-or-nothing in the future. For example if the whole token API is made to work outside a proc macro, but the diagnostics API via Span (warn, error, note, etc) would not be available.

bjorn3 · 2021-06-25T17:56:49Z

If the token api is made to work outside a proc macro, but the diagnostics api is not, I think users of proc_macro can just access the token api without checking is_available and maybe only check the rustc version. Usage of the diagnostics api should then still be behind a is_available check. Basically if it always works, is_available shouldn't be used, but if it only works inside a proc macro, is_available should be used.

bjorn3 · 2021-06-25T17:59:27Z

I would really like for this feature to be stabilized. proc_macro2 is currently unusable with cg_clif outside of proc macros, as it checks if a proc macro function panics when being called. cg_clif doesn't yet support unwinding on panics. Also if the function proc_macro2 checks becomes available outside of a proc macro, that will break proc_macro2 usage outside of proc macros, so the sooner it migrates to is_available the better.

smklein · 2021-07-15T20:43:51Z

I would really like for this feature to be stabilized. proc_macro2 is currently unusable with cg_clif outside of proc macros, as it checks if a proc macro function panics when being called. cg_clif doesn't yet support unwinding on panics. Also if the function proc_macro2 checks becomes available outside of a proc macro, that will break proc_macro2 usage outside of proc macros, so the sooner it migrates to is_available the better.

Does the workaround described here not work for you? I'm running into a similar use-case, but the proc_macro2::fallback::force() function is a sufficient escape-hatch for now

bjorn3 · 2021-07-15T20:52:37Z

That doesn't help when you don't control the source. proc-macro2 is used by a dependency of the user's project most of the time. And even if it isn't, I can't except users of cg_clif to always add proc_macro2::fallback::force() to their build scripts. I would like something that works out of the box.

m-ou-se · 2021-09-08T19:32:52Z

@rfcbot merge

rfcbot · 2021-09-08T19:32:53Z

Team member @m-ou-se has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

jhpratt · 2021-09-08T22:53:30Z

I still share the concern that some APIs (but not all) may, in the future, be permitted to be used in any context, not just proc macros. Wouldn't #[cfg(accessible(...))] encompass this and at the same time be more powerful, flexible, and forward-thinking?

bjorn3 · 2021-09-09T08:31:04Z

#[cfg(accessible(...))] only tests if the api exists at all in the current rustc version. It doesn't test if you can actually call it without getting a panic in the current context. For dependencies it is impossible to know if it will be run as part of a proc-macro or not. In addition a proc-macro may want to spawn a thread, in which case the thread isn't allowed to call into libproc_macro.

rfcbot · 2021-09-29T18:34:18Z

🔔 This is now entering its final comment period, as per the review above. 🔔

rfcbot · 2021-10-09T18:47:01Z

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

…lable, r=petrochenkov Stabilize proc_macro::is_available Tracking issue: rust-lang#71436 The FCP for the stabilization of `proc_macro::is_available` has completed.

2915: Update rust-toolchain to 2021-12-04 r=ppannuto a=lschuermann ### Pull Request Overview This pull request updates the Rust toolchain to version `1.59.0-nightly (efec54529 2021-12-04)`. The motivation for this change is that the `litex-sim-ci` breaks when compiling `elf2tab` on the previous toolchain version: ``` error[E0658]: use of unstable library feature 'proc_macro_is_available' --> /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/proc-macro2-1.0.33/src/detection.rs:28:21 | 28 | let available = proc_macro::is_available(); | ^^^^^^^^^^^^^^^^^^^^^^^^ | = note: see issue #71436 <rust-lang/rust#71436> for more information = help: add `#![feature(proc_macro_is_available)]` to the crate attributes to enable For more information about this error, try `rustc --explain E0658`. error: could not compile `proc-macro2` due to previous error warning: build failed, waiting for other jobs to finish... error: failed to compile `elf2tab v0.8.0`, intermediate artifacts can be found at `/tmp/cargo-installl05bA0` ``` Now, I'm not entirely sure as to why this happens. We haven't upgraded either of the Rust toolchain or `elf2tab`, and -- as far as I understand -- `cargo install elf2tab` should use the `Cargo.lock` file, so dependencies shouldn't change. In any case, this update seems to fix it. Besides the failing `litex-sim-ci` workflow, it seems like a good idea to pin a `rustc` version on which vital tools such as `elf2tab` properly compile. I can also reproduce the `elf2tab` build failure locally while the `rust-toolchain` of the Tock repository is used. ### Testing Strategy This pull request was tested by CI. ### TODO or Help Wanted N/A ### Documentation Updated - [x] ~Updated the relevant files in `/docs`,~ or no updates are required. ### Formatting - [x] Ran `make prepush`. Co-authored-by: Leon Schuermann <leon@is.currently.online>

The build currently fails as follows: error[E0658]: use of unstable library feature 'proc_macro_is_available' --> /home/penberg/.cargo/registry/src/github.com-1ecc6299db9ec823/proc-macro2-1.0.33/src/detection.rs:28:21 | 28 | let available = proc_macro::is_available(); | ^^^^^^^^^^^^^^^^^^^^^^^^ | = note: see issue #71436 <rust-lang/rust#71436> for more information = help: add `#![feature(proc_macro_is_available)]` to the crate attributes to enable For more information about this error, try `rustc --explain E0658`. error: could not compile `proc-macro2` due to previous error The problem is that the "null_terminated" crate depends on the "utf" with a relaxed "0.1" version, which causes cargo to pull a version that is incompatible with our toolchain. Fix up the dependency by relying on the old "0.1.5" version explicitly.

Fixes the following error: error[E0658]: use of unstable library feature 'proc_macro_is_available' --> /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/proc-macro2-1.0.33/src/detection.rs:28:21 | 28 | let available = proc_macro::is_available(); | ^^^^^^^^^^^^^^^^^^^^^^^^ | = note: see issue #71436 <rust-lang/rust#71436> for more information = help: add `#![feature(proc_macro_is_available)]` to the crate attributes to enable For more information about this error, try `rustc --explain E0658`. error: could not compile `proc-macro2` due to previous error

bjorn3 · 2023-06-22T20:04:22Z

You should update proc-macro2 (if you depend on it) and update to the latest rustc version.

jonas-schievink added the B-unstable Blocker: Implemented in the nightly compiler and unstable. label Apr 22, 2020

This was referenced Apr 25, 2020

Use proc_macro::is_available() instead of panic for proc macro detection dtolnay/proc-macro2#218

Closed

cxxbridge doesn't run with panic=abort dtolnay/cxx#130

Closed

Aaron1011 added the A-proc-macros Area: Procedural macros label May 21, 2020

KodrAus added the Libs-Tracked Libs issues that are tracked on the team's project board. label Jul 29, 2020

m-ou-se added the I-nominated label Sep 8, 2021

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rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Sep 8, 2021

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rfcbot removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Sep 8, 2021

m-ou-se removed the I-nominated label Sep 22, 2021

rfcbot added the final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. label Sep 29, 2021

rfcbot removed the proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. label Sep 29, 2021

rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. to-announce Announce this issue on triage meeting and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Oct 9, 2021

bjorn3 mentioned this issue Oct 10, 2021

Stabilize proc_macro::is_available #89735

Merged

m-ou-se closed this as completed Oct 12, 2021

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sea212 mentioned this issue Dec 8, 2021

[CICD] Fuzz test workflow fails zeitgeistpm/zeitgeist#403

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sgx_align_struct_attribute compile error apache/incubator-teaclave-sgx-sdk#364

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Tracking issue for proc_macro::is_available() #71436

Tracking issue for proc_macro::is_available() #71436

dtolnay commented Apr 22, 2020 •

edited by m-ou-se

Aaron1011 commented Jun 12, 2020

dtolnay commented Jun 12, 2020 •

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bjorn3 commented Jun 25, 2021

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smklein commented Jul 15, 2021 •

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bjorn3 commented Jul 15, 2021

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m-ou-se commented Sep 8, 2021

rfcbot commented Sep 8, 2021 •

edited by yaahc

jhpratt commented Sep 8, 2021 •

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bjorn3 commented Sep 9, 2021 •

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rfcbot commented Sep 29, 2021

rfcbot commented Oct 9, 2021

bjorn3 commented Jun 22, 2023

Tracking issue for proc_macro::is_available() #71436

Tracking issue for proc_macro::is_available() #71436

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dtolnay commented Apr 22, 2020 • edited by m-ou-se

About tracking issues

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Aaron1011 commented Jun 12, 2020

dtolnay commented Jun 12, 2020 • edited

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m-ou-se commented Sep 8, 2021

rfcbot commented Sep 8, 2021 • edited by yaahc

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rfcbot commented Sep 29, 2021

rfcbot commented Oct 9, 2021

bjorn3 commented Jun 22, 2023

dtolnay commented Apr 22, 2020 •

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dtolnay commented Jun 12, 2020 •

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smklein commented Jul 15, 2021 •

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rfcbot commented Sep 8, 2021 •

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jhpratt commented Sep 8, 2021 •

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