f*::NAN: guarantee that this is a quiet NaN #139483
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
rustbot added S-waiting-on-review 
RalfJung added the I-libs-api-nominated 
m-ou-se added T-libs-api 
| @rfcbot merge |
| 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 added proposed-final-comment-period 
tbu- reviewed Apr 7, 2025
| The Miri subtree was changed cc @rust-lang/miri |
rfcbot added final-comment-period | 🔔 This is now entering its final comment period, as per the review above. 🔔 |
| Is it worth considering the alternative of making no guarantees about |
| I think adding a |
rfcbot added finished-final-comment-period | 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. |
tgross35 approved these changes Apr 17, 2025
| r? tgross35 |
bors added the S-waiting-on-bors 
bors added a commit to rust-lang-ci/rust that referenced this pull request Apr 17, 2025
…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
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Apr 18, 2025
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.
| 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
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 what's the best way to get the top mantissa bit for our various float types? |
| I think |
ChrisDenton added a commit to ChrisDenton/rust that referenced this pull request Apr 22, 2025
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
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
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
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
test_nan: ensure the NAN contant is quiet Follow-up to rust-lang#139483 r? ``@tgross35``
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Jun 29, 2025
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
10 participants
Add this suggestion to a batch that can be applied as a single commit. This suggestion is invalid because no changes were made to the code. Suggestions cannot be applied while the pull request is closed. Suggestions cannot be applied while viewing a subset of changes. Only one suggestion per line can be applied in a batch. Add this suggestion to a batch that can be applied as a single commit. Applying suggestions on deleted lines is not supported. You must change the existing code in this line in order to create a valid suggestion. Outdated suggestions cannot be applied. This suggestion has been applied or marked resolved. Suggestions cannot be applied from pending reviews. Suggestions cannot be applied on multi-line comments. Suggestions cannot be applied while the pull request is queued to merge. Suggestion cannot be applied right now. Please check back later.
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 write0.0 / 0.0instead 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.