您可以将 mut i8 转换为 i32 吗?
Can you convert a mut i8 into an i32?
我正在尝试构建一个小型终端仿真器,但 运行 与 libc 发生了一些有趣的类型冲突。当我尝试设置 pty 连接的从属部分时,我需要通过对 ptsname() 的系统调用来创建从属部分,以便获取 pts 的名称,以便我可以访问它。但是,我收到一个类型错误,指出 libc::ptsname() 需要 i32 作为输入。这与说明应该传递文件描述符的手册页直接冲突。我只是想知道我是否可以将文件描述符的 libc::c_int 转换为 i32 以传递给 ptsname。
代码如下:
use libc::{self, c_int, grantpt, posix_openpt, ptsname, unlockpt, O_RDWR};
use std::os::unix::io::FromRawFd;
use std::process::{Child, Command, Stdio};
#[derive(Debug)]
pub struct Pty {
process: Child,
fd: i32,
}
fn create_pty(process: &str) -> Pty {
let master: c_int;
unsafe {
// create master/slave pair of fd
master = posix_openpt(O_RDWR);
if master == -1 {
panic!("Failed to posix_openpt");
}
// set slave ownership and mode as master
let mut result = grantpt(master);
if result == -1 {
panic!("Failed to grantpt");
}
// unlock slave
result = unlockpt(master);
if result == -1 {
panic!("Failed to unlockpt");
}
}
let slave: c_int = ptsname(master as i32);
slave = libc::open(slave);
let mut builder = Command::new(process);
match builder.spawn() {
Ok(process) => {
let pty = Pty {
process,
fd: master,
};
pty
}
Err(e) => {
panic!("Failed to create pty: {}", e);
}
}
}
fn main() {
let shell = "/bin/bish";
let pty = create_pty(shell);
println!("{:?}", pty);
}
和控制台输出(第二个错误暂时可以忽略):
error[E0308]: mismatched types
--> src/main.rs:42:24
|
42 | let slave: c_int = ptsname(master as i32);
| ^^^^^^^^^^^^^^^^^^^^^^ expected i32, found *-ptr
|
= note: expected type `i32`
found type `*mut i8`
error[E0060]: this function takes at least 2 parameters but 1 parameter was supplied
--> src/main.rs:43:13
|
43 | slave = libc::open(slave);
| ^^^^^^^^^^^^^^^^^ expected at least 2 parameters
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0060, E0308.
For more information about an error, try `rustc --explain E0060`.
error: could not compile `experiment`.
这并不是说它需要 i32
的 输入 ,而是你要问 ptsname(master as i32);
的类型是 i32
.这可能有点令人困惑,因为 c_int
是 i32
的别名,所以它听起来像是在要求一个不相关的类型。
问题是您给 slave
类型 c_int
,而 ptsname
returns *mut c_char
(c_char
也是别名,这次是 i8
).
我正在尝试构建一个小型终端仿真器,但 运行 与 libc 发生了一些有趣的类型冲突。当我尝试设置 pty 连接的从属部分时,我需要通过对 ptsname() 的系统调用来创建从属部分,以便获取 pts 的名称,以便我可以访问它。但是,我收到一个类型错误,指出 libc::ptsname() 需要 i32 作为输入。这与说明应该传递文件描述符的手册页直接冲突。我只是想知道我是否可以将文件描述符的 libc::c_int 转换为 i32 以传递给 ptsname。
代码如下:
use libc::{self, c_int, grantpt, posix_openpt, ptsname, unlockpt, O_RDWR};
use std::os::unix::io::FromRawFd;
use std::process::{Child, Command, Stdio};
#[derive(Debug)]
pub struct Pty {
process: Child,
fd: i32,
}
fn create_pty(process: &str) -> Pty {
let master: c_int;
unsafe {
// create master/slave pair of fd
master = posix_openpt(O_RDWR);
if master == -1 {
panic!("Failed to posix_openpt");
}
// set slave ownership and mode as master
let mut result = grantpt(master);
if result == -1 {
panic!("Failed to grantpt");
}
// unlock slave
result = unlockpt(master);
if result == -1 {
panic!("Failed to unlockpt");
}
}
let slave: c_int = ptsname(master as i32);
slave = libc::open(slave);
let mut builder = Command::new(process);
match builder.spawn() {
Ok(process) => {
let pty = Pty {
process,
fd: master,
};
pty
}
Err(e) => {
panic!("Failed to create pty: {}", e);
}
}
}
fn main() {
let shell = "/bin/bish";
let pty = create_pty(shell);
println!("{:?}", pty);
}
和控制台输出(第二个错误暂时可以忽略):
error[E0308]: mismatched types
--> src/main.rs:42:24
|
42 | let slave: c_int = ptsname(master as i32);
| ^^^^^^^^^^^^^^^^^^^^^^ expected i32, found *-ptr
|
= note: expected type `i32`
found type `*mut i8`
error[E0060]: this function takes at least 2 parameters but 1 parameter was supplied
--> src/main.rs:43:13
|
43 | slave = libc::open(slave);
| ^^^^^^^^^^^^^^^^^ expected at least 2 parameters
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0060, E0308.
For more information about an error, try `rustc --explain E0060`.
error: could not compile `experiment`.
这并不是说它需要 i32
的 输入 ,而是你要问 ptsname(master as i32);
的类型是 i32
.这可能有点令人困惑,因为 c_int
是 i32
的别名,所以它听起来像是在要求一个不相关的类型。
问题是您给 slave
类型 c_int
,而 ptsname
returns *mut c_char
(c_char
也是别名,这次是 i8
).