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454ae9fb8b
avoid mixing accesses of ptrs derived from a mutable ref and parent ptrs ``@Vanille-N`` is working on a successor for Stacked Borrows. It will mostly accept strictly more code than Stacked Borrows did, with one exception: the following pattern no longer works. ```rust let mut root = 6u8; let mref = &mut root; let ptr = mref as *mut u8; *ptr = 0; // Write assert_eq!(root, 0); // Parent Read *ptr = 0; // Attempted Write ``` This worked in Stacked Borrows kind of by accident: when doing the "parent read", under SB we Disable `mref`, but the raw ptrs derived from it remain usable. The fact that we can still use the "children" of a reference that is no longer usable is quite nasty and leads to some undesirable effects (in particular it is the major blocker for resolving https://github.com/rust-lang/unsafe-code-guidelines/issues/257). So in Tree Borrows we no longer do that; instead, reading from `root` makes `mref` and all its children read-only. Due to other improvements in Tree Borrows, the entire Miri test suite still passes with this new behavior, and even the entire libcore and liballoc test suite, except for these 2 cases this PR fixes. Both of these involve code where the programmer wrote `&mut` but then used pointers derived from that reference in ways that alias with the parent pointer, which arguably is violating uniqueness. They are fixed by properly using raw pointers throughout. |
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| rtstartup | ||
| rustc-std-workspace-alloc | ||
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| rustc-std-workspace-std | ||
| std | ||
| stdarch@a0c30f3e3c | ||
| test | ||
| unwind | ||