Undefined behavior: zero-initialization of Event

[askeksa]

As I understand it, we need to fix this to prevent this code from panicking in a future version of Rust.

Quoting @RalfJung from the discussion of #112:

The bug is here:

vst-rs/src/api.rs

Line 488 in d7d5b6f

/// # let mut event: *mut Event = &mut unsafe { std::mem::zeroed() };

and here:

vst-rs/src/api.rs

Line 503 in d7d5b6f

/// # let mut event: *mut Event = &mut unsafe { std::mem::zeroed() };

EventType contains no variant with tag discriminant 0, so creating one via mem::zeroed() is Undefined Behavior.

[RalfJung]

Yes, thanks for opening an issue. :)

The easiest fix is probably to have some variant with discriminant 0, that would then be the one that is used by a std::mem::zeroed() event. Alternatively, maybe you could avoid unsafe code entirely and derive(Default) for Event, and then impl Default for EventType to determine what the default event type should be.

[Boscop]

I just ran into this, my plugin panics when I try to load it, e.g. in the simple_host that's part of the examples.
It crashes in this line:

vst-rs/src/buffer.rs

Line 397 in f0b7fd3

let api_events = vec![unsafe { mem::zeroed::<PlaceholderEvent>() }; capacity];

because SysExEvent contains an EventType.

Could we please fix this soon? :)
(I really need this VST to function..)

thread '<unnamed>' panicked at 'attempted to zero-initialize type `api::SysExEve
nt`, which is invalid', /rustc/b1496c6e606dd908dd651ac2cce89815e10d7fc5\library\
core\src\mem\mod.rs:623:9
stack backtrace:
   0: std::panicking::begin_panic_handler
             at /rustc/b1496c6e606dd908dd651ac2cce89815e10d7fc5\/library\std\src
\panicking.rs:483
   1: core::panicking::panic_fmt
             at /rustc/b1496c6e606dd908dd651ac2cce89815e10d7fc5\/library\core\sr
c\panicking.rs:85
   2: core::panicking::panic
             at /rustc/b1496c6e606dd908dd651ac2cce89815e10d7fc5\/library\core\sr
c\panicking.rs:50
   3: core::mem::zeroed
             at /rustc/b1496c6e606dd908dd651ac2cce89815e10d7fc5\library\core\src
\mem\mod.rs:623
   4: vst::buffer::SendEventBuffer::new
             at C:\Users\me\.cargo\registry\src\github.com-1ecc6299db9ec823\vst-
0.2.0\src\buffer.rs:397
   5: vst::buffer::{{impl}}::default
             at C:\Users\me\.cargo\registry\src\github.com-1ecc6299db9ec823\vst-
0.2.0\src\buffer.rs:386

[RalfJung]

Indeed, the UB check that causes a panic here has landed in the mean time. Cc rust-lang/rust#66151

[askeksa]

I will take a look at this over the weekend.