https://github.com/rust-lang/rust/issues/97889
https://dev-doc.rust-lang.org/beta/unstable-book/language-features/unix-sigpipe.html#unix_sigpipe
自 2014 年起，Unix 平台上的 Rust 运行时就将SIGPIPE信号处理器设置为SIG_IGN（忽略）。然而，应用程序可能有充分理由需要不同的行为，因此提供了一个-Zon-broken-pipe编译器标志，可用于在fn main()被调用前选择如何设置SIGPIPE（如果要更改的话）。
-Z 开头的参数是不稳定的编译器特性，只能在 nightly 版本中使用
如果使用的是 stable 版本的 Rust，这个参数将不被支持// std/src/rt.rs
// One-time runtime initialization.
// Runs before `main`.
// SAFETY: must be called only once during runtime initialization.
// NOTE: this is not guaranteed to run, for example when Rust code is called externally.
//
// # The `sigpipe` parameter
//
// Since 2014, the Rust runtime on Unix has set the `SIGPIPE` handler to
// `SIG_IGN`. Applications have good reasons to want a different behavior
// though, so there is a `-Zon-broken-pipe` compiler flag that
// can be used to select how `SIGPIPE` shall be setup (if changed at all) before
// `fn main()` is called. See <https://github.com/rust-lang/rust/issues/97889>
// for more info.
//
// The `sigpipe` parameter to this function gets its value via the code that
// rustc generates to invoke `fn lang_start()`. The reason we have `sigpipe` for
// all platforms and not only Unix, is because std is not allowed to have `cfg`
// directives as this high level. See the module docs in
// `src/tools/tidy/src/pal.rs` for more info. On all other platforms, `sigpipe`
// has a value, but its value is ignored.
//
// Even though it is an `u8`, it only ever has 4 values. These are documented in
// `compiler/rustc_session/src/config/sigpipe.rs`.
#[cfg_attr(test, allow(dead_code))]
unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
#[cfg_attr(target_os = "teeos", allow(unused_unsafe))]
unsafe {
sys::init(argc, argv, sigpipe)
};
// Remember the main thread ID to give it the correct name.
// SAFETY: this is the only time and place where we call this function.
unsafe { main_thread::set(thread::current_id()) };
}