Skip to content

f*::NAN: guarantee that this is a quiet NaN#139483

Merged
bors merged 2 commits intorust-lang:masterfrom
RalfJung:nan
Apr 18, 2025
Merged

f*::NAN: guarantee that this is a quiet NaN#139483
bors merged 2 commits intorust-lang:masterfrom
RalfJung:nan

Conversation

@RalfJung
Copy link
Member

@RalfJung RalfJung commented Apr 7, 2025

I think we should guarantee that this is a quiet NaN. This then implies that programs not using f*::from_bits (or unsafe type conversions) are guaranteed to only work with quiet NaNs. It would be awkward if people start to write 0.0 / 0.0 instead of using the constant just because they want to get a guaranteed-quiet NaN.

This is a @rust-lang/libs-api change. The definition of this constant currently is 0.0 / 0.0, which is already guaranteed to be a quiet NaN. So all this does is forward that guarantee to our users.

@rustbot
Copy link
Collaborator

rustbot commented Apr 7, 2025

r? @thomcc

rustbot has assigned @thomcc.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 7, 2025
@RalfJung RalfJung added the I-libs-api-nominated Nominated for discussion during a libs-api team meeting. label Apr 7, 2025
@m-ou-se m-ou-se added T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. S-waiting-on-fcp Status: PR is in FCP and is awaiting for FCP to complete. and removed T-libs Relevant to the library team, which will review and decide on the PR/issue. S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. I-libs-api-nominated Nominated for discussion during a libs-api team meeting. labels Apr 7, 2025
@m-ou-se
Copy link
Member

m-ou-se commented Apr 7, 2025

@rfcbot merge

@rfcbot
Copy link

rfcbot commented Apr 7, 2025 •
edited by joshtriplett
Loading

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.

@rfcbot 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 Apr 7, 2025
tbu-
tbu- reviewed Apr 7, 2025
View reviewed changes
@rustbot
Copy link
Collaborator

rustbot commented Apr 7, 2025

The Miri subtree was changed

cc @rust-lang/miri

@rfcbot rfcbot added final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. and removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. labels Apr 7, 2025
@rfcbot
Copy link

rfcbot commented Apr 7, 2025

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

@m-ou-se m-ou-se mentioned this pull request Apr 7, 2025
Closed
@RalfJung RalfJung mentioned this pull request Apr 7, 2025
Merged
@bstrie
Copy link
Contributor

bstrie commented Apr 10, 2025

Is it worth considering the alternative of making no guarantees about f*::NAN, and instead providing f*::QUIET_NAN and f*::SIGNALING_NAN?

@RalfJung
Copy link
Member Author

RalfJung commented Apr 10, 2025 •
edited
Loading

I think adding a SIGNALING_NAN might be worth considering, but I'd say NAN is the better name for QUIET_NAN since it's what you should use most of the time. Signaling NaNs show non-portable behavior much more quickly than quiet NaNs.

@rfcbot 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 Apr 17, 2025
@rfcbot
Copy link

rfcbot commented Apr 17, 2025

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.

@rustbot rustbot mentioned this pull request Apr 17, 2025
Closed
@tgross35
Copy link
Contributor

tgross35 commented Apr 17, 2025

r? tgross35
@bors r+ rollup

@bors
Copy link
Collaborator

bors commented Apr 17, 2025

📌 Commit 0da46d1 has been approved by tgross35

It is now in the queue for this repository.

@bors bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Apr 17, 2025
@matthiaskrgr matthiaskrgr mentioned this pull request Apr 17, 2025
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Apr 17, 2025
@bors
Auto merge of rust-lang#139992 - matthiaskrgr:rollup-ak3uibu, r=matth…
1f76d21 
…iaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#139351 (Autodiff batching2)
 - rust-lang#139483 (f*::NAN: guarantee that this is a quiet NaN)
 - rust-lang#139498 (Ignore zero-sized types in wasm future-compat warning)
 - rust-lang#139967 (Introduce and use specialized `//@ ignore-auxiliary` for test support files instead of using `//@ ignore-test`)
 - rust-lang#139969 (update libc)
 - rust-lang#139971 (Make C string merging test work on MIPS)
 - rust-lang#139974 (Change `InterpCx::instantiate*` function visibility to pub)
 - rust-lang#139977 (Fix drop handling in `hint::select_unpredictable`)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit b6e48d3 into rust-lang:master Apr 18, 2025
6 checks passed
@rustbot rustbot added this to the 1.88.0 milestone Apr 18, 2025
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Apr 18, 2025
@rust-timer
Unrolled build for rust-lang#139483
4f7be40 
Rollup merge of rust-lang#139483 - RalfJung:nan, r=tgross35

f*::NAN: guarantee that this is a quiet NaN

I think we should guarantee that this is a quiet NaN. This then implies that programs not using `f*::from_bits` (or unsafe type conversions) are guaranteed to only work with quiet NaNs. It would be awkward if people start to write `0.0 / 0.0` instead of using the constant just because they want to get a guaranteed-quiet NaN.

This is a `@rust-lang/libs-api` change. The definition of this constant currently is `0.0 / 0.0`, which is already guaranteed to be a quiet NaN. So all this does is forward that guarantee to our users.
@tgross35
Copy link
Contributor

tgross35 commented Apr 18, 2025

I didn't think of this until just now but we should add a test ensuring the top mantissa bit is set

github-actions bot pushed a commit to model-checking/verify-rust-std that referenced this pull request Apr 19, 2025
@matthiaskrgr
Rollup merge of rust-lang#139483 - RalfJung:nan, r=tgross35
9267d04 
f*::NAN: guarantee that this is a quiet NaN

I think we should guarantee that this is a quiet NaN. This then implies that programs not using `f*::from_bits` (or unsafe type conversions) are guaranteed to only work with quiet NaNs. It would be awkward if people start to write `0.0 / 0.0` instead of using the constant just because they want to get a guaranteed-quiet NaN.

This is a `@rust-lang/libs-api` change. The definition of this constant currently is `0.0 / 0.0`, which is already guaranteed to be a quiet NaN. So all this does is forward that guarantee to our users.
@RalfJung RalfJung deleted the nan branch April 20, 2025 09:12
@RalfJung
Copy link
Member Author

RalfJung commented Apr 20, 2025

@tgross35 what's the best way to get the top mantissa bit for our various float types?

@tgross35
Copy link
Contributor

tgross35 commented Apr 20, 2025

I think x.to_bits() & (1 << (F::MANTISSA_DIGITS - 2)) != 0 should work

@RalfJung RalfJung mentioned this pull request Apr 22, 2025
Merged
ChrisDenton added a commit to ChrisDenton/rust that referenced this pull request Apr 22, 2025
@ChrisDenton
Rollup merge of rust-lang#140149 - RalfJung:test_nan, r=tgross35
6864ec4 
test_nan: ensure the NAN contant is quiet

Follow-up to rust-lang#139483

r? `@tgross35`
ChrisDenton added a commit to ChrisDenton/rust that referenced this pull request Apr 22, 2025
@ChrisDenton
Rollup merge of rust-lang#140149 - RalfJung:test_nan, r=tgross35
2d8264f 
test_nan: ensure the NAN contant is quiet

Follow-up to rust-lang#139483

r? ``@tgross35``
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Apr 23, 2025
@rust-timer
Unrolled build for rust-lang#140149
d10696a 
Rollup merge of rust-lang#140149 - RalfJung:test_nan, r=tgross35

test_nan: ensure the NAN contant is quiet

Follow-up to rust-lang#139483

r? ``@tgross35``
github-actions bot pushed a commit to rust-lang/miri that referenced this pull request Apr 23, 2025
@ChrisDenton
Rollup merge of #140149 - RalfJung:test_nan, r=tgross35
15af173 
test_nan: ensure the NAN contant is quiet

Follow-up to rust-lang/rust#139483

r? ``@tgross35``
github-actions bot pushed a commit to model-checking/verify-rust-std that referenced this pull request Apr 24, 2025
@ChrisDenton
Rollup merge of rust-lang#140149 - RalfJung:test_nan, r=tgross35
6532696 
test_nan: ensure the NAN contant is quiet

Follow-up to rust-lang#139483

r? ``@tgross35``
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Apr 30, 2025
@Mark-Simulacrum Mark-Simulacrum mentioned this pull request May 26, 2025
Closed
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Jun 29, 2025
@he32
rust188: add a package for rust 1.88.0.
8d94680 
Pkgsrc changes:
 * Adjust patches to adapt to upstream changes and new versions.
 * associated checksums

Upstream changes relative to 1.87.0:

Version 1.88.0 (2025-06-26)
==========================

Language
--------
- [Stabilize `#![feature(let_chains)]` in the 2024 edition.]
  (rust-lang/rust#132833)
  This feature allows `&&`-chaining `let` statements inside `if`
  and `while`, allowing intermixture with boolean expressions. The
  patterns inside the `let` sub-expressions can be irrefutable or
  refutable.
- [Stabilize `#![feature(naked_functions)]`.]
  (rust-lang/rust#134213)
  Naked functions allow writing functions with no compiler-generated
  epilogue and prologue, allowing full control over the generated
  assembly for a particular function.
- [Stabilize `#![feature(cfg_boolean_literals)]`.]
  (rust-lang/rust#138632)
  This allows using boolean literals as `cfg` predicates, e.g.
  `#[cfg(true)]` and `#[cfg(false)]`.
- [Fully de-stabilize the `#[bench]` attribute]
  (rust-lang/rust#134273). Usage of `#[bench]`
  without `#![feature(custom_test_frameworks)]` already triggered
  a deny-by-default future-incompatibility lint since Rust 1.77,
  but will now become a hard error.
- [Add warn-by-default `dangerous_implicit_autorefs` lint against
  implicit autoref of raw pointer dereference.]
  (rust-lang/rust#123239) The
  lint [will be bumped to deny-by-default]
  (rust-lang/rust#141661) in the next
  version of Rust.
- [Add `invalid_null_arguments` lint to prevent invalid usage of
  null pointers.] (rust-lang/rust#119220)
  This lint is uplifted from `clippy::invalid_null_ptr_usage`.
- [Change trait impl candidate preference for builtin impls and
  trivial where-clauses.] (rust-lang/rust#138176)
- [Check types of generic const parameter defaults]
  (rust-lang/rust#139646)

Compiler
--------
- [Stabilize `-Cdwarf-version` for selecting the version of DWARF
  debug information to generate.]
  (rust-lang/rust#136926)

Platform Support
----------------
- [Demote `i686-pc-windows-gnu` to Tier 2.]
  (https://blog.rust-lang.org/2025/05/26/demoting-i686-pc-windows-gnu/)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

[platform-support-doc]: https://doc.rust-lang.org/rustc/platform-support.html

Libraries
---------
- [Remove backticks from `#[should_panic]` test failure message.]
  (rust-lang/rust#136160)
- [Guarantee that `[T; N]::from_fn` is generated in order of
  increasing indices.] (rust-lang/rust#139099),
  for those passing it a stateful closure.
- [The libtest flag `--nocapture` is deprecated in favor of the
  more consistent `--no-capture` flag.]
  (rust-lang/rust#139224)
- [Guarantee that `{float}::NAN` is a quiet NaN.]
  (rust-lang/rust#139483)

Stabilized APIs
---------------

- [`Cell::update`]
  (https://doc.rust-lang.org/stable/std/cell/struct.Cell.html#method.update)
- [`impl Default for *const T`]
  (https://doc.rust-lang.org/nightly/std/primitive.pointer.html#impl-Default-for-*const+T)
- [`impl Default for *mut T`]
  (https://doc.rust-lang.org/nightly/std/primitive.pointer.html#impl-Default-for-*mut+T)
- [`HashMap::extract_if`]
  (https://doc.rust-lang.org/stable/std/collections/struct.HashMap.html#method.extract_if)
- [`HashSet::extract_if`]
  (https://doc.rust-lang.org/stable/std/collections/struct.HashSet.html#method.extract_if)
- [`proc_macro::Span::line`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Span.html#method.line)
- [`proc_macro::Span::column`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Span.html#method.column)
- [`proc_macro::Span::start`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Span.html#method.start)
- [`proc_macro::Span::end`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Span.html#method.end)
- [`proc_macro::Span::file`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Span.html#method.file)
- [`proc_macro::Span::local_file`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Span.html#method.local_file)

These previously stable APIs are now stable in const contexts:

- [`NonNull<T>::replace`]
  (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.replace)
- [`<*mut T>::replace`]
  (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.replace)
- [`std::ptr::swap_nonoverlapping`]
  (rust-lang/rust#137280)
- [`Cell::{replace, get, get_mut, from_mut, as_slice_of_cells}`]
  (rust-lang/rust#137928)

Cargo
-----
- [Stabilize automatic garbage collection.]
  (rust-lang/cargo#14287)
- [use `zlib-rs` for gzip compression in rust code]
  (rust-lang/cargo#15417)

Rustdoc
-----
- [Doctests can be ignored based on target names using `ignore-*` attributes.]
  (rust-lang/rust#137096)
- [Stabilize the `--test-runtool` and `--test-runtool-arg` CLI
  options to specify a program (like qemu) and its arguments to run
  a doctest.] (rust-lang/rust#137096)

Compatibility Notes
-------------------
- [Finish changing the internal representation of pasted tokens]
  (rust-lang/rust#124141). Certain invalid
  declarative macros that were previously accepted in obscure
  circumstances are now correctly rejected by the compiler. Use of
  a `tt` fragment specifier can often fix these macros.
- [Fully de-stabilize the `#[bench]` attribute]
  (rust-lang/rust#134273). Usage of `#[bench]`
  without `#![feature(custom_test_frameworks)]` already triggered
  a deny-by-default future-incompatibility lint since Rust 1.77,
  but will now become a hard error.
- [Fix borrow checking some always-true patterns.]
  (rust-lang/rust#139042) The borrow checker
  was overly permissive in some cases, allowing programs that
  shouldn't have compiled.
- [Update the minimum external LLVM to 19.]
  (rust-lang/rust#139275)
- [Make it a hard error to use a vector type with a non-Rust ABI
  without enabling the required target feature.]
  (rust-lang/rust#139309)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@tgross35 tgross35 tgross35 approved these changes

+1 more reviewer

@tbu- tbu- tbu- left review comments

Reviewers whose approvals may not affect merge requirements

Assignees

@tgross35 tgross35

Labels

disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. finished-final-comment-period The final comment period is finished for this PR / Issue. needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. S-waiting-on-fcp Status: PR is in FCP and is awaiting for FCP to complete. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue.

Projects

None yet

Milestone

1.88.0

Development

Successfully merging this pull request may close these issues.

10 participants

@RalfJung @rustbot @m-ou-se @rfcbot @bstrie @tgross35 @bors @tbu- @thomcc @apiraino

Comments