[SOLVED] Jack audio client name longer than 4 characters breaks client

Jack audio client name longer than 4 characters breaks client

Trying to use the JACK-AUDIO-CONNECTION-KIT from Rust (documentation), I run into problems calling

jack_client_t* jack_client_open (   const char *    client_name,
                                    jack_options_t  options,
                                    jack_status_t *     status,
                                    ... )

In Rust I use

#[link(name = "jack")]
extern "C" {
    pub fn jack_client_open(name: *const libc::c_char,
                        options: JackOptions,
                        status: &JackStatus)
                        -> *mut JackClientT;
}

(complete code)

When I use a name with four characters it works, e.g.

let name = CString::new("yass").unwrap().as_ptr();

but if I use 5 or more characters it doesn't work. In the JACK docs linked to above, it says that the name can be at most int jack_client_name_size() characters long, which is 64 in my case. Why does this happen?

Solution

let name = CString::new("yass").unwrap().as_ptr(); allocates a string, gets a pointer to it... then throws away the string, so you get a use-after-free. Don't do this. Write let name = CString::new("yass").unwrap();, then use name.as_ptr(). See also CStr::as_ptr and this RFC proposal.

Any suggestions to improve the documentation would be welcome.