Split large unsafe function slide #2406
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The old slice was doing several things at the same time: demonstrating both external functions as well as unsafe Rust functions. We now treat those two topics separately. In addition, the “Calling Unsafe Functions” heading has become its own slide with a non-crashing example that shows what can go wrong if an argument is misunderstood in a call to an unsafe function. The old example didn’t actually illustrate the danger clearly: it would produce mangled UTF-8 output, which the Playground server refuses to print.
djmitche
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Oct 28, 2024
| @@ -207,6 +207,9 @@ | |||
| - [Mutable Static Variables](unsafe-rust/mutable-static.md) | |||
| - [Unions](unsafe-rust/unions.md) | |||
| - [Unsafe Functions](unsafe-rust/unsafe-functions.md) | |||
| - [Unsafe External Functions](unsafe-rust/unsafe-extern-c-functions.md) | |||
| - [Unsafe Rust Functions](unsafe-rust/unsafe-rust-functions.md) | |||
| - [Calling Unsafe Functions](unsafe-rust/calling-unsafe-functions.md) | |||
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For subslides, we've used a subdirectory to contain the subslides. Also, only the top-level slide has the timing information. See src/methods-and-traits/traits for an example.
| /// | ||
| /// # Safety | ||
| /// | ||
| /// The pointers must be valid and properly aligned. |
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| Note that unsafe code is allowed within an unsafe function without an `unsafe` | ||
| block. We can prohibit this with `#[deny(unsafe_op_in_unsafe_fn)]`. Try adding | ||
| it and see what happens. This will likely change in a future Rust edition. |
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rust-lang/rust#120535 in the 2024 edition, in fact!
| `abs` is unsafe because it is an external function (FFI). Calling external | ||
| functions is usually only a problem when those functions do things with pointers | ||
| which might violate Rust's memory model, but in general any C function might | ||
| have undefined behaviour under any arbitrary circumstances. |
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Is it worth mentioning here that there is no automatic checking of the Rust function signature against that of the target function? For example, in this case the C function might take uint64_t and this would cause UB.
Co-authored-by: Dustin J. Mitchell <[email protected]>
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The old slice was doing several things at the same time: demonstrating
both external functions as well as unsafe Rust functions.
We now treat those two topics separately. In addition, the “Calling
Unsafe Functions” heading has become its own slide with a non-crashing
example that shows what can go wrong if an argument is misunderstood
in a call to an unsafe function. The old example didn’t actually
illustrate the danger clearly: it would produce mangled UTF-8 output,
which the Playground server refuses to print.
Part of #2445.