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rust-lang#49496 introduced specialization based on: ``` unsafe impl<T: ?Sized> IsZero for *mut T { fn is_zero(&self) -> bool { (*self).is_null() } } ``` … to call `RawVec::with_capacity_zeroed` for creating `Vec<*mut T>`, which is incorrect for fat pointers since `<*mut T>::is_null` only looks at the data component. That is, a fat pointer can be “null” without being made entirely of zero bits. This commit fixes it by removing the `?Sized` bound on this impl (and the corresponding `*const T` one). This regresses `vec![x; n]` with `x` a null raw slice of length zero, but that seems exceptionally uncommon. (Vtable pointers are never null, so raw trait objects would not take the fast path anyway. An alternative to keep the `?Sized` bound (or even generalize to `impl<U: Copy> IsZero for U`) would be to cast to `&[u8]` of length `size_of::<U>()`, but the optimizer seems not to be able to propagate alignment information and sticks with comparing one byte at a time: https://rust.godbolt.org/z/xQFkwL ---- Without the library change, the new test fails as follows: ``` ---- vec::vec_macro_repeating_null_raw_fat_pointer stdout ---- [src/liballoc/tests/vec.rs:1301] ptr_metadata(raw_dyn) = 0x00005596ef95f9a8 [src/liballoc/tests/vec.rs:1306] ptr_metadata(vec[0]) = 0x0000000000000000 thread 'vec::vec_macro_repeating_null_raw_fat_pointer' panicked at 'assertion failed: vec[0] == null_raw_dyn', src/liballoc/tests/vec.rs:1307:5 ```
…d `Option<Box<T>>`
Add long error explanation for E0495 Part of rust-lang#61137.
Use https for curl when building for linux I noticed that the dist-x86_64-linux builder uses http to fetch curl and doesn't do any signature verification. It should probably use https. r? @alexcrichton @Mark-Simulacrum
…-e0550, r=oli-obk Add long error explanation for E0550 Part of rust-lang#61137
…ackler Fix `vec![x; n]` with null raw fat pointer zeroing the pointer metadata rust-lang#49496 introduced specialization based on: ```rust unsafe impl<T: ?Sized> IsZero for *mut T { fn is_zero(&self) -> bool { (*self).is_null() } } ``` … to call `RawVec::with_capacity_zeroed` for creating `Vec<*mut T>`, which is incorrect for fat pointers since `<*mut T>::is_null` only looks at the data component. That is, a fat pointer can be “null” without being made entirely of zero bits. This commit fixes it by removing the `?Sized` bound on this impl (and the corresponding `*const T` one). This regresses `vec![x; n]` with `x` a null raw slice of length zero, but that seems exceptionally uncommon. (Vtable pointers are never null, so raw trait objects would not take the fast path anyway.) An alternative to keep the `?Sized` bound (or even generalize to `impl<U: Copy> IsZero for U`) would be to cast to `&[u8]` of length `size_of::<U>()`, but the optimizer seems not to be able to propagate alignment information and sticks with comparing one byte at a time: https://rust.godbolt.org/z/xQFkwL ---- Without the library change, the new test fails as follows: ```rust ---- vec::vec_macro_repeating_null_raw_fat_pointer stdout ---- [src/liballoc/tests/vec.rs:1301] ptr_metadata(raw_dyn) = 0x00005596ef95f9a8 [src/liballoc/tests/vec.rs:1306] ptr_metadata(vec[0]) = 0x0000000000000000 thread 'vec::vec_macro_repeating_null_raw_fat_pointer' panicked at 'assertion failed: vec[0] == null_raw_dyn', src/liballoc/tests/vec.rs:1307:5 ```
…ckler Zero-initialize `vec![None; n]` for `Option<&T>`, `Option<&mut T>` and `Option<Box<T>>`
Fixed a misleading documentation issue rust-lang#64844 Made the suggested change from @steveklabnik on issue rust-lang#64844
Add test for issue-64662 Closes rust-lang#64662 r? @varkor
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@bors r+ p=7 rollup=never |
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📌 Commit 80739a9 has been approved by |
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⌛ Testing commit 80739a9 with merge 55b76427bf6e3a64b4a9e1bfd6ca6cf84000674a... |
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💔 Test failed - checks-azure |
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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Closing in favor of #64932 |
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Successful merges:
vec![x; n]with null raw fat pointer zeroing the pointer metadata #64891 (Fixvec![x; n]with null raw fat pointer zeroing the pointer metadata)vec![None; n]forOption<&T>,Option<&mut T>andOption<Box<T>>#64893 (Zero-initializevec![None; n]forOption<&T>,Option<&mut T>andOption<Box<T>>)std::optionmodule #64844)Failed merges:
r? @ghost