fix str mutating through a ptr derived from &self #58200
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r? @Kimundi (rust_highfive has picked a reviewer for you, use r? to override) |
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RalfJung
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Feb 6, 2019
| let len = self.end - self.start; | ||
| super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr as *mut u8, len)) | ||
| super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, len)) |
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Notice that this raw ptr cast here is the "canary" that gave away that the old code was wrong -- it was actually casting *const u8 to *mut u8, which should not have been necessary.
SimonSapin
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src/libcore/str/mod.rs
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| /// modified in a way that it remains valid UTF-8. | ||
| /// | ||
| /// [`u8`]: primitive.u8.html | ||
| #[unstable(feature = "str_as_mut_ptr", issue = "0")] |
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r+ with a tracking issue
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I opened a tracking issue in #58215, please check if that looks all right.
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@bors r=SimonSapin |
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📌 Commit a996f2c has been approved by |
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Turns out there was another bad use of @SimonSapin could you review? |
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@bors r+ |
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📌 Commit 66c894e has been approved by |
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Centril
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Feb 13, 2019
fix str mutating through a ptr derived from &self Found by Miri: In `get_unchecked_mut` (also used by the checked variants internally) uses `str::as_ptr` to create a mutable reference, but `as_ptr` takes `&self`. This means the mutable references we return here got created from a shared reference, which violates the shared-references-are-read-only discipline! For this by using a newly introduced `as_mut_ptr` instead.
Centril
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Feb 13, 2019
fix str mutating through a ptr derived from &self Found by Miri: In `get_unchecked_mut` (also used by the checked variants internally) uses `str::as_ptr` to create a mutable reference, but `as_ptr` takes `&self`. This means the mutable references we return here got created from a shared reference, which violates the shared-references-are-read-only discipline! For this by using a newly introduced `as_mut_ptr` instead.
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Feb 13, 2019
Rollup of 13 pull requests Successful merges: - #57693 (Doc rewording) - #57815 (Speed up the fast path for assert_eq! and assert_ne!) - #58034 (Stabilize the time_checked_add feature) - #58057 (Stabilize linker-plugin based LTO (aka cross-language LTO)) - #58137 (Cleanup: rename node_id_to_type(_opt)) - #58166 (allow shorthand syntax for deprecation reason) - #58196 (Add specific feature gate error for const-unstable features) - #58200 (fix str mutating through a ptr derived from &self) - #58273 (Rename rustc_errors dependency in rust 2018 crates) - #58289 (impl iter() for dyn Error) - #58387 (Disallow `auto` trait alias syntax) - #58404 (use Ubuntu keyserver for CloudABI ports) - #58405 (Remove some dead code from libcore) Failed merges: r? @ghost
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Feb 13, 2019
fix str mutating through a ptr derived from &self Found by Miri: In `get_unchecked_mut` (also used by the checked variants internally) uses `str::as_ptr` to create a mutable reference, but `as_ptr` takes `&self`. This means the mutable references we return here got created from a shared reference, which violates the shared-references-are-read-only discipline! For this by using a newly introduced `as_mut_ptr` instead.
bors
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Feb 13, 2019
Rollup of 12 pull requests Successful merges: - #57693 (Doc rewording) - #57815 (Speed up the fast path for assert_eq! and assert_ne!) - #58034 (Stabilize the time_checked_add feature) - #58057 (Stabilize linker-plugin based LTO (aka cross-language LTO)) - #58137 (Cleanup: rename node_id_to_type(_opt)) - #58166 (allow shorthand syntax for deprecation reason) - #58200 (fix str mutating through a ptr derived from &self) - #58273 (Rename rustc_errors dependency in rust 2018 crates) - #58289 (impl iter() for dyn Error) - #58387 (Disallow `auto` trait alias syntax) - #58404 (use Ubuntu keyserver for CloudABI ports) - #58405 (Remove some dead code from libcore) Failed merges: r? @ghost
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May 14, 2019
as_ptr returns a read-only pointer Add comments to `as_ptr` methods to warn that these are read-only pointers, and writing to them is UB. [It was pointed out](https://internals.rust-lang.org/t/as-ptr-vs-as-mut-ptr/9940) that `CStr` does not even have an `as_mut_ptr`. I originally was going to add one, but there is no method at all that would mutate a `CStr`. Was that a deliberate choice or should I add an `as_mut_ptr` (similar to [what I did for `str`](rust-lang#58200))?
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Found by Miri: In
get_unchecked_mut(also used by the checked variants internally) usesstr::as_ptrto create a mutable reference, butas_ptrtakes&self. This means the mutable references we return here got created from a shared reference, which violates the shared-references-are-read-only discipline!For this by using a newly introduced
as_mut_ptrinstead.