Unsafe 函数

调用 Unsafe 函数

如果函数或方法具有额外的前提条件，您必须遵守这些前提条件来避免未定义的行为， 则可以将该函数或方法标记为 unsafe：

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编写 Unsafe 函数

如果您自己编写的函数需要满足特定条件以避免未定义的行为， 您可以将这些函数标记为 unsafe。

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Speaker Notes

 This slide should take about 5 minutes.

调用 Unsafe 函数

get_unchecked, like most _unchecked functions, is unsafe, because it can create UB if the range is incorrect. abs is incorrect for a different reason: 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.

本例中的“C”是 ABI；也可以使用其他 ABI。

编写 Unsafe 函数

We wouldn’t actually use pointers for a swap function - it can be done safely with references.

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.