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remove const_raw_ptr_to_usize_cast feature #87020

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merged 3 commits into from Jul 10, 2021
Merged

remove const_raw_ptr_to_usize_cast feature #87020

merged 3 commits into from Jul 10, 2021

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RalfJung
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This feature currently has the strange status of "const-only unsafe", which was an experiment that we no longer think is a good idea. We need to find better ways to enable things like "messing with the low bits of a pointer" during CTFE.

r? @oli-obk

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 10, 2021
RalfJung
RalfJung commented Jul 10, 2021
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compiler/rustc_mir/src/transform/check_consts/ops.rs
@@ -397,9 +397,13 @@ impl NonConstOp for PanicNonStr {
}
}

/// Comparing raw pointers for equality.
/// Not currently intended to ever be allowed, even behind a feature gate: operation depends on
/// allocation base addresses that are not known at compile-time.
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Are there any other "ops" that should get a comment like this?

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well... there are similarly unallowable things. thread local statics, static mut, inline asm, ... they aren't really different, just more obvious?

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Hm yeah those are less subtle.

RalfJung
RalfJung commented Jul 10, 2021
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src/test/ui/consts/issue-52432.rs
//~| ERROR: type annotations needed
[(); &(static || {}) as *const _ as usize];
//~^ ERROR: closures cannot be static
//~| ERROR evaluation of constant value failed
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I think this has long stopped testing the right thing... looks like someone adjusted the expected errors without realizing that this makes the test pointless.

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Ah, looks like this was actually about testing an ICE: #66331.
But with the feature gate gone I don't think keeping the test makes a lot of sense.

@RalfJung RalfJung force-pushed the const_raw_ptr_to_usize_cast branch from 368cf15 to 1a40c3d Compare July 10, 2021 09:50
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@RalfJung RalfJung force-pushed the const_raw_ptr_to_usize_cast branch from 1a40c3d to 5f0dd6d Compare July 10, 2021 10:09
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@RalfJung RalfJung force-pushed the const_raw_ptr_to_usize_cast branch from 8c70d09 to f5094aa Compare July 10, 2021 11:48
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oli-obk commented Jul 10, 2021

@bors r+

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bors commented Jul 10, 2021

📌 Commit f5094aa has been approved by oli-obk

@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 Jul 10, 2021
@JohnTitor JohnTitor mentioned this pull request Jul 10, 2021
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bors added a commit to rust-lang-ci/rust that referenced this pull request Jul 10, 2021
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Auto merge of rust-lang#87029 - JohnTitor:rollup-0yapv7z, r=JohnTitor
a31431f 
Rollup of 5 pull requests

Successful merges:

 - rust-lang#87006 (Revert the revert of renaming traits::VTable to ImplSource)
 - rust-lang#87011 (avoid reentrant lock acquire when ThreadIds run out)
 - rust-lang#87013 (Fix several ICEs related to malformed `#[repr(...)]` attributes)
 - rust-lang#87020 (remove const_raw_ptr_to_usize_cast feature)
 - rust-lang#87028 (Fix type: `'satic` -> `'static`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit ad2a0fc into rust-lang:master Jul 10, 2021
@rustbot rustbot added this to the 1.55.0 milestone Jul 10, 2021
@RalfJung RalfJung deleted the const_raw_ptr_to_usize_cast branch July 11, 2021 12:04
@timothee-haudebourg timothee-haudebourg mentioned this pull request Jul 28, 2021
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@RalfJung RalfJung mentioned this pull request Sep 16, 2021
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