Added warning around code with reference to uninit bytes #64123
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Thanks! @bors r+ rollup |
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…ut_uninit_integers, r=Centril Added warning around code with reference to uninit bytes Officially, uninitialized integers, and therefore, Rust references to them are _invalid_ (note that this may evolve into official defined behavior (_c.f._, rust-lang/unsafe-code-guidelines#71)). However, `::std` uses references to uninitialized integers when working with the `Read::initializer` feature (rust-lang#42788), since it relies on this unstably having defined behavior with the current implementation of the compiler (IIUC). Hence the comment to disincentivize people from using this pattern outside the standard library.
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Rollup of 10 pull requests Successful merges: - #63166 (Add Result::cloned{,_err} and Result::copied{,_err}) - #63930 (Account for doc comments coming from proc macros without spans) - #63985 (Stabilize pin_into_inner in 1.39.0) - #64023 (libstd fuchsia fixes) - #64030 (Fix unlock ordering in SGX synchronization primitives) - #64041 (use TokenStream rather than &[TokenTree] for built-in macros) - #64043 (Add some more tests for underscore imports) - #64092 (Update xLTO compatibility table in rustc book.) - #64120 (Move path parsing earlier) - #64123 (Added warning around code with reference to uninit bytes) Failed merges: r? @ghost
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…ut_uninit_integers, r=Centril Added warning around code with reference to uninit bytes Officially, uninitialized integers, and therefore, Rust references to them are _invalid_ (note that this may evolve into official defined behavior (_c.f._, rust-lang/unsafe-code-guidelines#71)). However, `::std` uses references to uninitialized integers when working with the `Read::initializer` feature (rust-lang#42788), since it relies on this unstably having defined behavior with the current implementation of the compiler (IIUC). Hence the comment to disincentivize people from using this pattern outside the standard library.
Centril
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Sep 5, 2019
…ut_uninit_integers, r=Centril Added warning around code with reference to uninit bytes Officially, uninitialized integers, and therefore, Rust references to them are _invalid_ (note that this may evolve into official defined behavior (_c.f._, rust-lang/unsafe-code-guidelines#71)). However, `::std` uses references to uninitialized integers when working with the `Read::initializer` feature (rust-lang#42788), since it relies on this unstably having defined behavior with the current implementation of the compiler (IIUC). Hence the comment to disincentivize people from using this pattern outside the standard library.
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Sep 5, 2019
Rollup of 15 pull requests Successful merges: - #62860 (Stabilize checked_duration_since for 1.38.0) - #63549 (Rev::rposition counts from the wrong end) - #63985 (Stabilize pin_into_inner in 1.39.0) - #64005 (Add a `Place::is_indirect` method to determine whether a `Place` contains a `Deref` projection) - #64031 (Harden `param_attrs` test wrt. usage of a proc macro `#[attr]`) - #64038 (Check impl trait substs when checking for recursive types) - #64043 (Add some more tests for underscore imports) - #64092 (Update xLTO compatibility table in rustc book.) - #64110 (Refer to "`self` type" instead of "receiver type") - #64120 (Move path parsing earlier) - #64123 (Added warning around code with reference to uninit bytes) - #64128 (unused_parens: account for or-patterns and `&(mut x)`) - #64141 (Minimize uses of `LocalInternedString`) - #64142 (Fix doc links in `std::cmp` module) - #64148 (fix a few typos in comments) Failed merges: r? @ghost
RalfJung
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Sep 5, 2019
| // | ||
| // - Only the standard library gets to soundly "ignore" this, | ||
| // based on its privileged knowledge of unstable rustc | ||
| // internals; |
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Notice however that this calls out-of-libstd code (r.read). So the issue here is not entirely contaned within the standard library.
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Officially, uninitialized integers, and therefore, Rust references to them are invalid (note that this may evolve into official defined behavior (c.f., rust-lang/unsafe-code-guidelines#71)).
However,
::stduses references to uninitialized integers when working with theRead::initializerfeature (#42788), since it relies on this unstably having defined behavior with the current implementation of the compiler (IIUC).Hence the comment to disincentivize people from using this pattern outside the standard library.