3 //! The `rt` module provides a narrow set of runtime services,
4 //! including the global heap (exported in `heap`) and unwinding and
5 //! backtrace support. The APIs in this module are highly unstable,
6 //! and should be considered as private implementation details for the
11 reason
= "this public module should not exist and is highly likely \
16 #![deny(unsafe_op_in_unsafe_fn)]
17 #![allow(unused_macros)]
19 use crate::ffi
::CString
;
21 // Re-export some of our utilities which are expected by other crates.
22 pub use crate::panicking
::{begin_panic, panic_count}
;
23 pub use core
::panicking
::{panic_display, panic_fmt}
;
25 use crate::sync
::Once
;
27 use crate::sys_common
::thread_info
;
28 use crate::thread
::Thread
;
30 // Prints to the "panic output", depending on the platform this may be:
31 // - the standard error output
32 // - some dedicated platform specific output
33 // - nothing (so this macro is a no-op)
34 macro_rules
! rtprintpanic
{
36 if let Some(mut out
) = crate::sys
::stdio
::panic_output() {
37 let _
= crate::io
::Write
::write_fmt(&mut out
, format_args
!($
($t
)*));
42 macro_rules
! rtabort
{
45 rtprintpanic
!("fatal runtime error: {}\n", format_args
!($
($t
)*));
46 crate::sys
::abort_internal();
51 macro_rules
! rtassert
{
54 rtabort
!(concat
!("assertion failed: ", stringify
!($e
)));
59 macro_rules
! rtunwrap
{
60 ($ok
:ident
, $e
:expr
) => {
64 let err
= err
.as_ref().map(drop
); // map Ok/Some which might not be Debug
65 rtabort
!(concat
!("unwrap failed: ", stringify
!($e
), " = {:?}"), err
)
71 // One-time runtime initialization.
72 // Runs before `main`.
73 // SAFETY: must be called only once during runtime initialization.
74 // NOTE: this is not guaranteed to run, for example when Rust code is called externally.
75 #[cfg_attr(test, allow(dead_code))]
76 unsafe fn init(argc
: isize, argv
: *const *const u8) {
78 sys
::init(argc
, argv
);
80 let main_guard
= sys
::thread
::guard
::init();
81 // Next, set up the current Thread with the guard information we just
82 // created. Note that this isn't necessary in general for new threads,
83 // but we just do this to name the main thread and to give it correct
84 // info about the stack bounds.
85 let thread
= Thread
::new(Some(rtunwrap
!(Ok
, CString
::new("main"))));
86 thread_info
::set(main_guard
, thread
);
90 // One-time runtime cleanup.
91 // Runs after `main` or at program exit.
92 // NOTE: this is not guaranteed to run, for example when the program aborts.
93 pub(crate) fn cleanup() {
94 static CLEANUP
: Once
= Once
::new();
95 CLEANUP
.call_once(|| unsafe {
96 // Flush stdout and disable buffering.
98 // SAFETY: Only called once during runtime cleanup.
103 // To reduce the generated code of the new `lang_start`, this function is doing
106 fn lang_start_internal(
107 main
: &(dyn Fn() -> i32 + Sync
+ crate::panic
::RefUnwindSafe
),
109 argv
: *const *const u8,
110 ) -> Result
<isize, !> {
111 use crate::{mem, panic}
;
112 let rt_abort
= move |e
| {
114 rtabort
!("initialization or cleanup bug");
116 // Guard against the code called by this function from unwinding outside of the Rust-controlled
117 // code, which is UB. This is a requirement imposed by a combination of how the
118 // `#[lang="start"]` attribute is implemented as well as by the implementation of the panicking
121 // There are a couple of instances where unwinding can begin. First is inside of the
122 // `rt::init`, `rt::cleanup` and similar functions controlled by libstd. In those instances a
123 // panic is a libstd implementation bug. A quite likely one too, as there isn't any way to
124 // prevent libstd from accidentally introducing a panic to these functions. Another is from
125 // user code from `main` or, more nefariously, as described in e.g. issue #86030.
126 // SAFETY: Only called once during runtime initialization.
127 panic
::catch_unwind(move || unsafe { init(argc, argv) }
).map_err(rt_abort
)?
;
128 let ret_code
= panic
::catch_unwind(move || panic
::catch_unwind(main
).unwrap_or(101) as isize)
131 rtabort
!("drop of the panic payload panicked");
133 panic
::catch_unwind(cleanup
).map_err(rt_abort
)?
;
139 fn lang_start
<T
: crate::process
::Termination
+ '
static>(
142 argv
: *const *const u8,
144 let Ok(v
) = lang_start_internal(
145 &move || crate::sys_common
::backtrace
::__rust_begin_short_backtrace(main
).report(),