do not use const stability attribute when we don't even need to call the intrinsic in const #1497
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…the intrinsic in const
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r? @Amanieu (rustbot has picked a reviewer for you, use r? to override) |
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revert stabilization of const_intrinsic_copy `@rust-lang/wg-const-eval` I don't know what we were thinking when we approved rust-lang#97276... const-eval isn't supposed to be able to mutate anything yet! It's also near impossible to actually call `copy` in const on stable since `&mut` expressions are generally unstable. However, there's one exception... ```rust static mut INT: i32 = unsafe { let val = &mut [1]; // `&mut` on arrays is allowed in `static mut` (val as *mut [i32; 1]).copy_from(&[42], 1); val[0] }; fn main() { unsafe { dbg!(INT); } } ``` Inside `static mut`, we accept some `&mut` since ~forever, to make `static mut FOO: &mut [T] = &mut [...];` work. We reject any attempt to actually write to that mutable reference though... except for the `copy` functions. I think we should revert stabilizing these functions that take `*mut`, and then re-stabilize them together with `ptr.write` once mutable references are stable. (This will likely fail on PowerPC until rust-lang/stdarch#1497 lands. But we'll need a crater run first anyway.)
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Nov 14, 2023
revert stabilization of const_intrinsic_copy `@rust-lang/wg-const-eval` I don't know what we were thinking when we approved rust-lang#97276... const-eval isn't supposed to be able to mutate anything yet! It's also near impossible to actually call `copy` in const on stable since `&mut` expressions are generally unstable. However, there's one exception... ```rust static mut INT: i32 = unsafe { let val = &mut [1]; // `&mut` on arrays is allowed in `static mut` (val as *mut [i32; 1]).copy_from(&[42], 1); val[0] }; fn main() { unsafe { dbg!(INT); } } ``` Inside `static mut`, we accept some `&mut` since ~forever, to make `static mut FOO: &mut [T] = &mut [...];` work. We reject any attempt to actually write to that mutable reference though... except for the `copy` functions. I think we should revert stabilizing these functions that take `*mut`, and then re-stabilize them together with `ptr.write` once mutable references are stable. (This will likely fail on PowerPC until rust-lang/stdarch#1497 lands. But we'll need a crater run first anyway.)
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Strangely it looks like my branch is not actually merged in this repo? Did this get rebased? rust-lang projects usually use merging and I find that a lot nicer than rebase -- it preserves which state the repo was in when I actually worked on this branch. Also with rebasing there's no way to detect which of my feature branches have already been merged so I have to delete them all by hand. |
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I think the repo was configured this way when I inherited it: it doesn't allow merging, only rebasing for PR. I don't have permissions to change the settings though. |
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Ideally there is a setting to autodelete the branch on merge no matter the merge strategy used |
That would help, but doesn't take care of the local versions of these feature branches in my checkouts. |
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revert stabilization of const_intrinsic_copy `@rust-lang/wg-const-eval` I don't know what we were thinking when we approved rust-lang#97276... const-eval isn't supposed to be able to mutate anything yet! It's also near impossible to actually call `copy` in const on stable since `&mut` expressions are generally unstable. However, there's one exception... ```rust static mut INT: i32 = unsafe { let val = &mut [1]; // `&mut` on arrays is allowed in `static mut` (val as *mut [i32; 1]).copy_from(&[42], 1); val[0] }; fn main() { unsafe { dbg!(INT); } } ``` Inside `static mut`, we accept some `&mut` since ~forever, to make `static mut FOO: &mut [T] = &mut [...];` work. We reject any attempt to actually write to that mutable reference though... except for the `copy` functions. I think we should revert stabilizing these functions that take `*mut`, and then re-stabilize them together with `ptr.write` once mutable references are stable. (This will likely fail on PowerPC until rust-lang/stdarch#1497 lands. But we'll need a crater run first anyway.)
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Feb 6, 2024
revert stabilization of const_intrinsic_copy `@rust-lang/wg-const-eval` I don't know what we were thinking when we approved rust-lang#97276... const-eval isn't supposed to be able to mutate anything yet! It's also near impossible to actually call `copy` in const on stable since `&mut` expressions are generally unstable. However, there's one exception... ```rust static mut INT: i32 = unsafe { let val = &mut [1]; // `&mut` on arrays is allowed in `static mut` (val as *mut [i32; 1]).copy_from(&[42], 1); val[0] }; fn main() { unsafe { dbg!(INT); } } ``` Inside `static mut`, we accept some `&mut` since ~forever, to make `static mut FOO: &mut [T] = &mut [...];` work. We reject any attempt to actually write to that mutable reference though... except for the `copy` functions. I think we should revert stabilizing these functions that take `*mut`, and then re-stabilize them together with `ptr.write` once mutable references are stable. (This will likely fail on PowerPC until rust-lang/stdarch#1497 lands. But we'll need a crater run first anyway.)
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revert stabilization of const_intrinsic_copy `@rust-lang/wg-const-eval` I don't know what we were thinking when we approved rust-lang/rust#97276... const-eval isn't supposed to be able to mutate anything yet! It's also near impossible to actually call `copy` in const on stable since `&mut` expressions are generally unstable. However, there's one exception... ```rust static mut INT: i32 = unsafe { let val = &mut [1]; // `&mut` on arrays is allowed in `static mut` (val as *mut [i32; 1]).copy_from(&[42], 1); val[0] }; fn main() { unsafe { dbg!(INT); } } ``` Inside `static mut`, we accept some `&mut` since ~forever, to make `static mut FOO: &mut [T] = &mut [...];` work. We reject any attempt to actually write to that mutable reference though... except for the `copy` functions. I think we should revert stabilizing these functions that take `*mut`, and then re-stabilize them together with `ptr.write` once mutable references are stable. (This will likely fail on PowerPC until rust-lang/stdarch#1497 lands. But we'll need a crater run first anyway.)
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Id' like to revert rust-lang/rust#97276 since we didn't actually mean to support writing to mutable references in
const. But that won't work if stdarch uses the stability attribute. I hope we can just remove it here, otherwise this will be a pain to land...