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make ptr::invalid not the same as a regular int2ptr cast #97219

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merged 1 commit into from
May 21, 2022

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@RalfJung RalfJung commented May 20, 2022

In Miri, we would like to distinguish ptr::invalid from ptr::from_exposed_provenance, so that we can provide better diagnostics issues like rust-lang/miri#2134, and so that we can detect the UB in programs like

fn main() {
    let x = 0u8;
    let original_ptr = &x as *const u8;
    let addr = original_ptr.expose_addr();
    let new_ptr: *const u8 = core::ptr::invalid(addr);
    unsafe {
        dbg!(*new_ptr);
    }
}

To achieve that, the two functions need to have different implementations. Currently, both are just as casts. We could add an intrinsic for this, but it turns out transmute already has the right behavior, at least as far as Miri is concerned. So I propose we just use that.

Cc @Gankra

@rustbot rustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label May 20, 2022
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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 20, 2022
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thomcc commented May 20, 2022

@bors r+

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bors commented May 20, 2022

📌 Commit 31c3c04 has been approved by thomcc

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 20, 2022
bors added a commit to rust-lang-ci/rust that referenced this pull request May 21, 2022
…laumeGomez

Rollup of 7 pull requests

Successful merges:

 - rust-lang#97190 (Add implicit call to from_str via parse in documentation)
 - rust-lang#97218 (Add eslint checks)
 - rust-lang#97219 (make ptr::invalid not the same as a regular int2ptr cast)
 - rust-lang#97223 (Remove quadratic behaviour from -Zunpretty=hir-tree.)
 - rust-lang#97232 (typo)
 - rust-lang#97237 (Add some more weird-exprs)
 - rust-lang#97238 (Bump LLVM fetched from CI to fix run-make)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 6fef5f1 into rust-lang:master May 21, 2022
@rustbot rustbot added this to the 1.63.0 milestone May 21, 2022
@RalfJung RalfJung deleted the ptr-invalid branch May 22, 2022 06:02
@RalfJung RalfJung mentioned this pull request May 23, 2022
bors added a commit to rust-lang/miri that referenced this pull request May 23, 2022
Rustup

In particular, this contains rust-lang/rust#97219. Miri support for actually erroring on misuse of `ptr::invalid` will happen later.

Also move some more tests to better locations.
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6 participants