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Rollup merge of #130350 - RalfJung:strict-provenance, r=dtolnay

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stabilize Strict Provenance and Exposed Provenance APIs

Given that [RFC 3559](https://rust-lang.github.io/rfcs/3559-rust-has-provenance.html) has been accepted, t-lang has approved the concept of provenance to exist in the language. So I think it's time that we stabilize the strict provenance and exposed provenance APIs, and discuss provenance explicitly in the docs:
```rust
// core::ptr
pub const fn without_provenance<T>(addr: usize) -> *const T;
pub const fn dangling<T>() -> *const T;
pub const fn without_provenance_mut<T>(addr: usize) -> *mut T;
pub const fn dangling_mut<T>() -> *mut T;
pub fn with_exposed_provenance<T>(addr: usize) -> *const T;
pub fn with_exposed_provenance_mut<T>(addr: usize) -> *mut T;

impl<T: ?Sized> *const T {
    pub fn addr(self) -> usize;
    pub fn expose_provenance(self) -> usize;
    pub fn with_addr(self, addr: usize) -> Self;
    pub fn map_addr(self, f: impl FnOnce(usize) -> usize) -> Self;
}

impl<T: ?Sized> *mut T {
    pub fn addr(self) -> usize;
    pub fn expose_provenance(self) -> usize;
    pub fn with_addr(self, addr: usize) -> Self;
    pub fn map_addr(self, f: impl FnOnce(usize) -> usize) -> Self;
}

impl<T: ?Sized> NonNull<T> {
    pub fn addr(self) -> NonZero<usize>;
    pub fn with_addr(self, addr: NonZero<usize>) -> Self;
    pub fn map_addr(self, f: impl FnOnce(NonZero<usize>) -> NonZero<usize>) -> Self;
}
```

I also did a pass over the docs to adjust them, because this is no longer an "experiment". The `ptr` docs now discuss the concept of provenance in general, and then they go into the two families of APIs for dealing with provenance: Strict Provenance and Exposed Provenance. I removed the discussion of how pointers also have an associated "address space" -- that is not actually tracked in the pointer value, it is tracked in the type, so IMO it just distracts from the core point of provenance. I also adjusted the docs for `with_exposed_provenance` to make it clear that we cannot guarantee much about this function, it's all best-effort.

There are two unstable lints associated with the strict_provenance feature gate; I moved them to a new [strict_provenance_lints](https://github.com/rust-lang/rust/issues/130351) feature since I didn't want this PR to have an even bigger FCP. ;)

`@rust-lang/opsem` Would be great to get some feedback on the docs here. :)
Nominating for `@rust-lang/libs-api.`

Part of https://github.com/rust-lang/rust/issues/95228.

[FCP comment](https://github.com/rust-lang/rust/pull/130350#issuecomment-2395114536)
This commit is contained in:
Matthias Krüger 2024-10-21 18:11:19 +02:00 • committed by GitHub
commit 20b1dadf92
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90 changed files with 363 additions and 525 deletions
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6
compiler/rustc_lint_defs/src/builtin.rs
View file

@ -2667,7 +2667,6 @@ declare_lint! {
/// ### Example
///
/// ```rust
/// #![feature(strict_provenance)]
/// #![warn(fuzzy_provenance_casts)]
///
/// fn main() {
@ -2701,7 +2700,7 @@ declare_lint! {
pub FUZZY_PROVENANCE_CASTS,
Allow,
"a fuzzy integer to pointer cast is used",
@feature_gate = strict_provenance;
@feature_gate = strict_provenance_lints;
}
declare_lint! {
@ -2711,7 +2710,6 @@ declare_lint! {
/// ### Example
///
/// ```rust
/// #![feature(strict_provenance)]
/// #![warn(lossy_provenance_casts)]
///
/// fn main() {
@ -2747,7 +2745,7 @@ declare_lint! {
pub LOSSY_PROVENANCE_CASTS,
Allow,
"a lossy pointer to integer cast is used",
@feature_gate = strict_provenance;
@feature_gate = strict_provenance_lints;
}
declare_lint! {