呼叫不安全的函式
呼叫不安全的函式
如果函式或方法具有額外先決條件,而您必須遵循這些條件才能避免未定義的行為,那麼就可以將該函式或方法標示為 unsafe
:
編寫不安全的函式
如果您的函式必須滿足特定條件才能避免未定義的行為,您可以將其標示為 unsafe
。
Speaker Notes
This slide should take about 5 minutes.
呼叫不安全的函式
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.
此例中的 "C"
為 ABI;您也可以使用其他 ABI。
編寫不安全的函式
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.