From 1c12b1be330dd9c3de0b4fe599686d7c0c45e720 Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Mon, 24 Jun 2019 22:58:53 +0200 Subject: call out explicitly that general read needs to be called with an initialized buffer --- src/libstd/io/mod.rs | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'src/libstd') diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs index 917199f8ea8..7fba844897f 100644 --- a/src/libstd/io/mod.rs +++ b/src/libstd/io/mod.rs @@ -506,9 +506,18 @@ pub trait Read { /// /// No guarantees are provided about the contents of `buf` when this /// function is called, implementations cannot rely on any property of the - /// contents of `buf` being true. It is recommended that implementations + /// contents of `buf` being true. It is recommended that *implementations* /// only write data to `buf` instead of reading its contents. /// + /// Correspondingly, however, *users* of this trait may not assume any guarantees + /// about how the implementation uses `buf`. The trait is safe to implement, + /// so it is perfectly possible that the implementation might inspect that data. + /// As a caller, it is your responsibility to make sure that `buf` is initialized + /// before calling `read`. Calling `read` with an uninitialized `buf` (of the kind one + /// obtains via [`MaybeUninit`]) is not safe, and can lead to undefined behavior. + /// + /// [`MaybeUninit`]: ../mem/union.MaybeUninit.html + /// /// # Errors /// /// If this function encounters any form of I/O or other error, an error -- cgit 1.4.1-3-g733a5