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a7813a04 XL |
1 | //! Implementation of various bits and pieces of the `panic!` macro and |
2 | //! associated runtime pieces. | |
3 | //! | |
4 | //! Specifically, this module contains the implementation of: | |
5 | //! | |
6 | //! * Panic hooks | |
7 | //! * Executing a panic up to doing the actual implementation | |
8 | //! * Shims around "try" | |
9 | ||
3dfed10e XL |
10 | #![deny(unsafe_op_in_unsafe_fn)] |
11 | ||
dfeec247 | 12 | use core::panic::{BoxMeUp, Location, PanicInfo}; |
532ac7d7 XL |
13 | |
14 | use crate::any::Any; | |
15 | use crate::fmt; | |
16 | use crate::intrinsics; | |
e74abb32 | 17 | use crate::mem::{self, ManuallyDrop}; |
dfeec247 | 18 | use crate::process; |
e74abb32 | 19 | use crate::sync::atomic::{AtomicBool, Ordering}; |
532ac7d7 | 20 | use crate::sys::stdio::panic_output; |
dfeec247 | 21 | use crate::sys_common::backtrace::{self, RustBacktrace}; |
17df50a5 XL |
22 | use crate::sys_common::rwlock::StaticRWLock; |
23 | use crate::sys_common::thread_info; | |
532ac7d7 XL |
24 | use crate::thread; |
25 | ||
26 | #[cfg(not(test))] | |
fc512014 | 27 | use crate::io::set_output_capture; |
532ac7d7 XL |
28 | // make sure to use the stderr output configured |
29 | // by libtest in the real copy of std | |
30 | #[cfg(test)] | |
fc512014 | 31 | use realstd::io::set_output_capture; |
1a4d82fc | 32 | |
a7813a04 XL |
33 | // Binary interface to the panic runtime that the standard library depends on. |
34 | // | |
35 | // The standard library is tagged with `#![needs_panic_runtime]` (introduced in | |
36 | // RFC 1513) to indicate that it requires some other crate tagged with | |
37 | // `#![panic_runtime]` to exist somewhere. Each panic runtime is intended to | |
38 | // implement these symbols (with the same signatures) so we can get matched up | |
39 | // to them. | |
40 | // | |
41 | // One day this may look a little less ad-hoc with the compiler helping out to | |
42 | // hook up these functions, but it is not this day! | |
43 | #[allow(improper_ctypes)] | |
dfeec247 | 44 | extern "C" { |
ba9703b0 | 45 | fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static); |
60c5eb7d | 46 | |
5869c6ff XL |
47 | /// `payload` is passed through another layer of raw pointers as `&mut dyn Trait` is not |
48 | /// FFI-safe. `BoxMeUp` lazily performs allocation only when needed (this avoids allocations | |
49 | /// when using the "abort" panic runtime). | |
83c7162d | 50 | #[unwind(allowed)] |
5869c6ff | 51 | fn __rust_start_panic(payload: *mut &mut dyn BoxMeUp) -> u32; |
a7813a04 XL |
52 | } |
53 | ||
dfeec247 XL |
54 | /// This function is called by the panic runtime if FFI code catches a Rust |
55 | /// panic but doesn't rethrow it. We don't support this case since it messes | |
56 | /// with our panic count. | |
57 | #[cfg(not(test))] | |
58 | #[rustc_std_internal_symbol] | |
59 | extern "C" fn __rust_drop_panic() -> ! { | |
60 | rtabort!("Rust panics must be rethrown"); | |
61 | } | |
62 | ||
1b1a35ee XL |
63 | /// This function is called by the panic runtime if it catches an exception |
64 | /// object which does not correspond to a Rust panic. | |
65 | #[cfg(not(test))] | |
66 | #[rustc_std_internal_symbol] | |
67 | extern "C" fn __rust_foreign_exception() -> ! { | |
68 | rtabort!("Rust cannot catch foreign exceptions"); | |
69 | } | |
70 | ||
9cc50fc6 | 71 | #[derive(Copy, Clone)] |
54a0048b | 72 | enum Hook { |
9cc50fc6 | 73 | Default, |
532ac7d7 | 74 | Custom(*mut (dyn Fn(&PanicInfo<'_>) + 'static + Sync + Send)), |
9cc50fc6 SL |
75 | } |
76 | ||
17df50a5 | 77 | static HOOK_LOCK: StaticRWLock = StaticRWLock::new(); |
54a0048b | 78 | static mut HOOK: Hook = Hook::Default; |
9cc50fc6 | 79 | |
54a0048b | 80 | /// Registers a custom panic hook, replacing any that was previously registered. |
9cc50fc6 | 81 | /// |
a7813a04 XL |
82 | /// The panic hook is invoked when a thread panics, but before the panic runtime |
83 | /// is invoked. As such, the hook will run with both the aborting and unwinding | |
84 | /// runtimes. The default hook prints a message to standard error and generates | |
85 | /// a backtrace if requested, but this behavior can be customized with the | |
83c7162d XL |
86 | /// `set_hook` and [`take_hook`] functions. |
87 | /// | |
88 | /// [`take_hook`]: ./fn.take_hook.html | |
9cc50fc6 | 89 | /// |
54a0048b | 90 | /// The hook is provided with a `PanicInfo` struct which contains information |
9cc50fc6 SL |
91 | /// about the origin of the panic, including the payload passed to `panic!` and |
92 | /// the source code location from which the panic originated. | |
93 | /// | |
54a0048b | 94 | /// The panic hook is a global resource. |
9cc50fc6 SL |
95 | /// |
96 | /// # Panics | |
97 | /// | |
98 | /// Panics if called from a panicking thread. | |
9e0c209e SL |
99 | /// |
100 | /// # Examples | |
101 | /// | |
102 | /// The following will print "Custom panic hook": | |
103 | /// | |
104 | /// ```should_panic | |
105 | /// use std::panic; | |
106 | /// | |
107 | /// panic::set_hook(Box::new(|_| { | |
108 | /// println!("Custom panic hook"); | |
109 | /// })); | |
110 | /// | |
111 | /// panic!("Normal panic"); | |
112 | /// ``` | |
a7813a04 | 113 | #[stable(feature = "panic_hooks", since = "1.10.0")] |
532ac7d7 | 114 | pub fn set_hook(hook: Box<dyn Fn(&PanicInfo<'_>) + 'static + Sync + Send>) { |
9cc50fc6 | 115 | if thread::panicking() { |
54a0048b | 116 | panic!("cannot modify the panic hook from a panicking thread"); |
9cc50fc6 SL |
117 | } |
118 | ||
9cc50fc6 | 119 | unsafe { |
17df50a5 | 120 | let guard = HOOK_LOCK.write(); |
54a0048b SL |
121 | let old_hook = HOOK; |
122 | HOOK = Hook::Custom(Box::into_raw(hook)); | |
17df50a5 | 123 | drop(guard); |
9cc50fc6 | 124 | |
54a0048b | 125 | if let Hook::Custom(ptr) = old_hook { |
dfeec247 XL |
126 | #[allow(unused_must_use)] |
127 | { | |
dc9dc135 XL |
128 | Box::from_raw(ptr); |
129 | } | |
9cc50fc6 SL |
130 | } |
131 | } | |
132 | } | |
133 | ||
54a0048b | 134 | /// Unregisters the current panic hook, returning it. |
9cc50fc6 | 135 | /// |
83c7162d XL |
136 | /// *See also the function [`set_hook`].* |
137 | /// | |
138 | /// [`set_hook`]: ./fn.set_hook.html | |
139 | /// | |
54a0048b | 140 | /// If no custom hook is registered, the default hook will be returned. |
9cc50fc6 SL |
141 | /// |
142 | /// # Panics | |
143 | /// | |
144 | /// Panics if called from a panicking thread. | |
9e0c209e SL |
145 | /// |
146 | /// # Examples | |
147 | /// | |
148 | /// The following will print "Normal panic": | |
149 | /// | |
150 | /// ```should_panic | |
151 | /// use std::panic; | |
152 | /// | |
153 | /// panic::set_hook(Box::new(|_| { | |
154 | /// println!("Custom panic hook"); | |
155 | /// })); | |
156 | /// | |
157 | /// let _ = panic::take_hook(); | |
158 | /// | |
159 | /// panic!("Normal panic"); | |
160 | /// ``` | |
a7813a04 | 161 | #[stable(feature = "panic_hooks", since = "1.10.0")] |
532ac7d7 | 162 | pub fn take_hook() -> Box<dyn Fn(&PanicInfo<'_>) + 'static + Sync + Send> { |
9cc50fc6 | 163 | if thread::panicking() { |
54a0048b | 164 | panic!("cannot modify the panic hook from a panicking thread"); |
9cc50fc6 SL |
165 | } |
166 | ||
167 | unsafe { | |
17df50a5 | 168 | let guard = HOOK_LOCK.write(); |
54a0048b SL |
169 | let hook = HOOK; |
170 | HOOK = Hook::Default; | |
17df50a5 | 171 | drop(guard); |
9cc50fc6 | 172 | |
54a0048b SL |
173 | match hook { |
174 | Hook::Default => Box::new(default_hook), | |
476ff2be | 175 | Hook::Custom(ptr) => Box::from_raw(ptr), |
9cc50fc6 SL |
176 | } |
177 | } | |
178 | } | |
179 | ||
532ac7d7 | 180 | fn default_hook(info: &PanicInfo<'_>) { |
9cc50fc6 SL |
181 | // If this is a double panic, make sure that we print a backtrace |
182 | // for this panic. Otherwise only print it if logging is enabled. | |
17df50a5 | 183 | let backtrace_env = if panic_count::get_count() >= 2 { |
3dfed10e | 184 | RustBacktrace::Print(crate::backtrace_rs::PrintFmt::Full) |
e1599b0c | 185 | } else { |
e74abb32 | 186 | backtrace::rust_backtrace_env() |
5bcae85e | 187 | }; |
9cc50fc6 | 188 | |
dc9dc135 XL |
189 | // The current implementation always returns `Some`. |
190 | let location = info.location().unwrap(); | |
9cc50fc6 | 191 | |
0531ce1d | 192 | let msg = match info.payload().downcast_ref::<&'static str>() { |
1a4d82fc | 193 | Some(s) => *s, |
0531ce1d | 194 | None => match info.payload().downcast_ref::<String>() { |
85aaf69f | 195 | Some(s) => &s[..], |
17df50a5 | 196 | None => "Box<dyn Any>", |
dfeec247 | 197 | }, |
1a4d82fc | 198 | }; |
d9579d0f AL |
199 | let thread = thread_info::current_thread(); |
200 | let name = thread.as_ref().and_then(|t| t.name()).unwrap_or("<unnamed>"); | |
b039eaaf | 201 | |
532ac7d7 | 202 | let write = |err: &mut dyn crate::io::Write| { |
dfeec247 | 203 | let _ = writeln!(err, "thread '{}' panicked at '{}', {}", name, msg, location); |
7453a54e | 204 | |
e74abb32 | 205 | static FIRST_PANIC: AtomicBool = AtomicBool::new(true); |
5bcae85e | 206 | |
e74abb32 XL |
207 | match backtrace_env { |
208 | RustBacktrace::Print(format) => drop(backtrace::print(err, format)), | |
209 | RustBacktrace::Disabled => {} | |
210 | RustBacktrace::RuntimeDisabled => { | |
211 | if FIRST_PANIC.swap(false, Ordering::SeqCst) { | |
dfeec247 XL |
212 | let _ = writeln!( |
213 | err, | |
f035d41b | 214 | "note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace" |
dfeec247 | 215 | ); |
e74abb32 | 216 | } |
5bcae85e | 217 | } |
b039eaaf SL |
218 | } |
219 | }; | |
220 | ||
fc512014 XL |
221 | if let Some(local) = set_output_capture(None) { |
222 | write(&mut *local.lock().unwrap_or_else(|e| e.into_inner())); | |
223 | set_output_capture(Some(local)); | |
0731742a XL |
224 | } else if let Some(mut out) = panic_output() { |
225 | write(&mut out); | |
1a4d82fc | 226 | } |
b039eaaf | 227 | } |
1a4d82fc | 228 | |
5bcae85e SL |
229 | #[cfg(not(test))] |
230 | #[doc(hidden)] | |
dfeec247 | 231 | #[unstable(feature = "update_panic_count", issue = "none")] |
f035d41b | 232 | pub mod panic_count { |
532ac7d7 | 233 | use crate::cell::Cell; |
f035d41b XL |
234 | use crate::sync::atomic::{AtomicUsize, Ordering}; |
235 | ||
17df50a5 XL |
236 | pub const ALWAYS_ABORT_FLAG: usize = 1 << (usize::BITS - 1); |
237 | ||
f035d41b XL |
238 | // Panic count for the current thread. |
239 | thread_local! { static LOCAL_PANIC_COUNT: Cell<usize> = Cell::new(0) } | |
240 | ||
241 | // Sum of panic counts from all threads. The purpose of this is to have | |
242 | // a fast path in `is_zero` (which is used by `panicking`). In any particular | |
243 | // thread, if that thread currently views `GLOBAL_PANIC_COUNT` as being zero, | |
244 | // then `LOCAL_PANIC_COUNT` in that thread is zero. This invariant holds before | |
245 | // and after increase and decrease, but not necessarily during their execution. | |
17df50a5 XL |
246 | // |
247 | // Additionally, the top bit of GLOBAL_PANIC_COUNT (GLOBAL_ALWAYS_ABORT_FLAG) | |
248 | // records whether panic::always_abort() has been called. This can only be | |
249 | // set, never cleared. | |
250 | // | |
251 | // This could be viewed as a struct containing a single bit and an n-1-bit | |
252 | // value, but if we wrote it like that it would be more than a single word, | |
253 | // and even a newtype around usize would be clumsy because we need atomics. | |
254 | // But we use such a tuple for the return type of increase(). | |
255 | // | |
256 | // Stealing a bit is fine because it just amounts to assuming that each | |
257 | // panicking thread consumes at least 2 bytes of address space. | |
f035d41b XL |
258 | static GLOBAL_PANIC_COUNT: AtomicUsize = AtomicUsize::new(0); |
259 | ||
17df50a5 XL |
260 | pub fn increase() -> (bool, usize) { |
261 | ( | |
262 | GLOBAL_PANIC_COUNT.fetch_add(1, Ordering::Relaxed) & ALWAYS_ABORT_FLAG != 0, | |
263 | LOCAL_PANIC_COUNT.with(|c| { | |
264 | let next = c.get() + 1; | |
265 | c.set(next); | |
266 | next | |
267 | }), | |
268 | ) | |
f035d41b XL |
269 | } |
270 | ||
17df50a5 | 271 | pub fn decrease() { |
f035d41b XL |
272 | GLOBAL_PANIC_COUNT.fetch_sub(1, Ordering::Relaxed); |
273 | LOCAL_PANIC_COUNT.with(|c| { | |
274 | let next = c.get() - 1; | |
275 | c.set(next); | |
276 | next | |
17df50a5 XL |
277 | }); |
278 | } | |
279 | ||
280 | pub fn set_always_abort() { | |
281 | GLOBAL_PANIC_COUNT.fetch_or(ALWAYS_ABORT_FLAG, Ordering::Relaxed); | |
f035d41b XL |
282 | } |
283 | ||
17df50a5 XL |
284 | // Disregards ALWAYS_ABORT_FLAG |
285 | pub fn get_count() -> usize { | |
f035d41b XL |
286 | LOCAL_PANIC_COUNT.with(|c| c.get()) |
287 | } | |
5bcae85e | 288 | |
17df50a5 | 289 | // Disregards ALWAYS_ABORT_FLAG |
f035d41b | 290 | #[inline] |
17df50a5 XL |
291 | pub fn count_is_zero() -> bool { |
292 | if GLOBAL_PANIC_COUNT.load(Ordering::Relaxed) & !ALWAYS_ABORT_FLAG == 0 { | |
f035d41b XL |
293 | // Fast path: if `GLOBAL_PANIC_COUNT` is zero, all threads |
294 | // (including the current one) will have `LOCAL_PANIC_COUNT` | |
295 | // equal to zero, so TLS access can be avoided. | |
296 | // | |
297 | // In terms of performance, a relaxed atomic load is similar to a normal | |
298 | // aligned memory read (e.g., a mov instruction in x86), but with some | |
299 | // compiler optimization restrictions. On the other hand, a TLS access | |
300 | // might require calling a non-inlinable function (such as `__tls_get_addr` | |
301 | // when using the GD TLS model). | |
302 | true | |
303 | } else { | |
304 | is_zero_slow_path() | |
305 | } | |
306 | } | |
307 | ||
308 | // Slow path is in a separate function to reduce the amount of code | |
309 | // inlined from `is_zero`. | |
310 | #[inline(never)] | |
311 | #[cold] | |
312 | fn is_zero_slow_path() -> bool { | |
313 | LOCAL_PANIC_COUNT.with(|c| c.get() == 0) | |
314 | } | |
5bcae85e SL |
315 | } |
316 | ||
317 | #[cfg(test)] | |
f035d41b | 318 | pub use realstd::rt::panic_count; |
5bcae85e | 319 | |
a7813a04 | 320 | /// Invoke a closure, capturing the cause of an unwinding panic if one occurs. |
532ac7d7 | 321 | pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> { |
8bb4bdeb | 322 | union Data<F, R> { |
e74abb32 XL |
323 | f: ManuallyDrop<F>, |
324 | r: ManuallyDrop<R>, | |
ba9703b0 | 325 | p: ManuallyDrop<Box<dyn Any + Send>>, |
5bcae85e | 326 | } |
a7813a04 | 327 | |
5bcae85e | 328 | // We do some sketchy operations with ownership here for the sake of |
ba9703b0 XL |
329 | // performance. We can only pass pointers down to `do_call` (can't pass |
330 | // objects by value), so we do all the ownership tracking here manually | |
331 | // using a union. | |
5bcae85e | 332 | // |
8bb4bdeb | 333 | // We go through a transition where: |
5bcae85e | 334 | // |
ba9703b0 | 335 | // * First, we set the data field `f` to be the argumentless closure that we're going to call. |
5bcae85e | 336 | // * When we make the function call, the `do_call` function below, we take |
ba9703b0 | 337 | // ownership of the function pointer. At this point the `data` union is |
8bb4bdeb | 338 | // entirely uninitialized. |
5bcae85e | 339 | // * If the closure successfully returns, we write the return value into the |
ba9703b0 XL |
340 | // data's return slot (field `r`). |
341 | // * If the closure panics (`do_catch` below), we write the panic payload into field `p`. | |
342 | // * Finally, when we come back out of the `try` intrinsic we're | |
5bcae85e SL |
343 | // in one of two states: |
344 | // | |
345 | // 1. The closure didn't panic, in which case the return value was | |
ba9703b0 XL |
346 | // filled in. We move it out of `data.r` and return it. |
347 | // 2. The closure panicked, in which case the panic payload was | |
348 | // filled in. We move it out of `data.p` and return it. | |
5bcae85e SL |
349 | // |
350 | // Once we stack all that together we should have the "most efficient' | |
351 | // method of calling a catch panic whilst juggling ownership. | |
dfeec247 | 352 | let mut data = Data { f: ManuallyDrop::new(f) }; |
b039eaaf | 353 | |
ba9703b0 | 354 | let data_ptr = &mut data as *mut _ as *mut u8; |
3dfed10e XL |
355 | // SAFETY: |
356 | // | |
357 | // Access to the union's fields: this is `std` and we know that the `r#try` | |
358 | // intrinsic fills in the `r` or `p` union field based on its return value. | |
359 | // | |
360 | // The call to `intrinsics::r#try` is made safe by: | |
361 | // - `do_call`, the first argument, can be called with the initial `data_ptr`. | |
362 | // - `do_catch`, the second argument, can be called with the `data_ptr` as well. | |
363 | // See their safety preconditions for more informations | |
364 | unsafe { | |
365 | return if intrinsics::r#try(do_call::<F, R>, data_ptr, do_catch::<F, R>) == 0 { | |
366 | Ok(ManuallyDrop::into_inner(data.r)) | |
367 | } else { | |
368 | Err(ManuallyDrop::into_inner(data.p)) | |
369 | }; | |
370 | } | |
a7813a04 | 371 | |
ba9703b0 XL |
372 | // We consider unwinding to be rare, so mark this function as cold. However, |
373 | // do not mark it no-inline -- that decision is best to leave to the | |
374 | // optimizer (in most cases this function is not inlined even as a normal, | |
375 | // non-cold function, though, as of the writing of this comment). | |
376 | #[cold] | |
377 | unsafe fn cleanup(payload: *mut u8) -> Box<dyn Any + Send + 'static> { | |
3dfed10e XL |
378 | // SAFETY: The whole unsafe block hinges on a correct implementation of |
379 | // the panic handler `__rust_panic_cleanup`. As such we can only | |
380 | // assume it returns the correct thing for `Box::from_raw` to work | |
381 | // without undefined behavior. | |
382 | let obj = unsafe { Box::from_raw(__rust_panic_cleanup(payload)) }; | |
f035d41b | 383 | panic_count::decrease(); |
ba9703b0 XL |
384 | obj |
385 | } | |
386 | ||
3dfed10e XL |
387 | // SAFETY: |
388 | // data must be non-NUL, correctly aligned, and a pointer to a `Data<F, R>` | |
389 | // Its must contains a valid `f` (type: F) value that can be use to fill | |
390 | // `data.r`. | |
391 | // | |
392 | // This function cannot be marked as `unsafe` because `intrinsics::r#try` | |
393 | // expects normal function pointers. | |
f9f354fc | 394 | #[inline] |
5bcae85e | 395 | fn do_call<F: FnOnce() -> R, R>(data: *mut u8) { |
3dfed10e | 396 | // SAFETY: this is the responsibilty of the caller, see above. |
5bcae85e SL |
397 | unsafe { |
398 | let data = data as *mut Data<F, R>; | |
e74abb32 XL |
399 | let data = &mut (*data); |
400 | let f = ManuallyDrop::take(&mut data.f); | |
401 | data.r = ManuallyDrop::new(f()); | |
5bcae85e | 402 | } |
a7813a04 | 403 | } |
ba9703b0 XL |
404 | |
405 | // We *do* want this part of the catch to be inlined: this allows the | |
406 | // compiler to properly track accesses to the Data union and optimize it | |
407 | // away most of the time. | |
3dfed10e XL |
408 | // |
409 | // SAFETY: | |
410 | // data must be non-NUL, correctly aligned, and a pointer to a `Data<F, R>` | |
411 | // Since this uses `cleanup` it also hinges on a correct implementation of | |
412 | // `__rustc_panic_cleanup`. | |
413 | // | |
414 | // This function cannot be marked as `unsafe` because `intrinsics::r#try` | |
415 | // expects normal function pointers. | |
ba9703b0 XL |
416 | #[inline] |
417 | fn do_catch<F: FnOnce() -> R, R>(data: *mut u8, payload: *mut u8) { | |
3dfed10e XL |
418 | // SAFETY: this is the responsibilty of the caller, see above. |
419 | // | |
420 | // When `__rustc_panic_cleaner` is correctly implemented we can rely | |
421 | // on `obj` being the correct thing to pass to `data.p` (after wrapping | |
422 | // in `ManuallyDrop`). | |
ba9703b0 XL |
423 | unsafe { |
424 | let data = data as *mut Data<F, R>; | |
425 | let data = &mut (*data); | |
426 | let obj = cleanup(payload); | |
427 | data.p = ManuallyDrop::new(obj); | |
428 | } | |
429 | } | |
a7813a04 XL |
430 | } |
431 | ||
432 | /// Determines whether the current thread is unwinding because of panic. | |
f035d41b | 433 | #[inline] |
a7813a04 | 434 | pub fn panicking() -> bool { |
17df50a5 | 435 | !panic_count::count_is_zero() |
a7813a04 XL |
436 | } |
437 | ||
a7813a04 XL |
438 | /// The entry point for panicking with a formatted message. |
439 | /// | |
440 | /// This is designed to reduce the amount of code required at the call | |
441 | /// site as much as possible (so that `panic!()` has as low an impact | |
442 | /// on (e.g.) the inlining of other functions as possible), by moving | |
443 | /// the actual formatting into this shared place. | |
dfeec247 | 444 | #[unstable(feature = "libstd_sys_internals", reason = "used by the panic! macro", issue = "none")] |
a1dfa0c6 XL |
445 | #[cold] |
446 | // If panic_immediate_abort, inline the abort call, | |
447 | // otherwise avoid inlining because of it is cold path. | |
dfeec247 XL |
448 | #[cfg_attr(not(feature = "panic_immediate_abort"), track_caller)] |
449 | #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))] | |
450 | #[cfg_attr(feature = "panic_immediate_abort", inline)] | |
451 | pub fn begin_panic_fmt(msg: &fmt::Arguments<'_>) -> ! { | |
a1dfa0c6 | 452 | if cfg!(feature = "panic_immediate_abort") { |
f035d41b | 453 | intrinsics::abort() |
a1dfa0c6 XL |
454 | } |
455 | ||
dfeec247 | 456 | let info = PanicInfo::internal_constructor(Some(msg), Location::caller()); |
60c5eb7d | 457 | begin_panic_handler(&info) |
94b46f34 | 458 | } |
83c7162d | 459 | |
60c5eb7d XL |
460 | /// Entry point of panics from the libcore crate (`panic_impl` lang item). |
461 | #[cfg_attr(not(test), panic_handler)] | |
462 | #[unwind(allowed)] | |
463 | pub fn begin_panic_handler(info: &PanicInfo<'_>) -> ! { | |
8faf50e0 XL |
464 | struct PanicPayload<'a> { |
465 | inner: &'a fmt::Arguments<'a>, | |
466 | string: Option<String>, | |
83c7162d XL |
467 | } |
468 | ||
8faf50e0 XL |
469 | impl<'a> PanicPayload<'a> { |
470 | fn new(inner: &'a fmt::Arguments<'a>) -> PanicPayload<'a> { | |
471 | PanicPayload { inner, string: None } | |
472 | } | |
83c7162d | 473 | |
8faf50e0 | 474 | fn fill(&mut self) -> &mut String { |
532ac7d7 | 475 | use crate::fmt::Write; |
83c7162d | 476 | |
8faf50e0 | 477 | let inner = self.inner; |
60c5eb7d | 478 | // Lazily, the first time this gets called, run the actual string formatting. |
8faf50e0 XL |
479 | self.string.get_or_insert_with(|| { |
480 | let mut s = String::new(); | |
481 | drop(s.write_fmt(*inner)); | |
482 | s | |
483 | }) | |
484 | } | |
94b46f34 | 485 | } |
83c7162d | 486 | |
8faf50e0 | 487 | unsafe impl<'a> BoxMeUp for PanicPayload<'a> { |
60c5eb7d | 488 | fn take_box(&mut self) -> *mut (dyn Any + Send) { |
dfeec247 XL |
489 | // We do two allocations here, unfortunately. But (a) they're required with the current |
490 | // scheme, and (b) we don't handle panic + OOM properly anyway (see comment in | |
491 | // begin_panic below). | |
416331ca | 492 | let contents = mem::take(self.fill()); |
8faf50e0 XL |
493 | Box::into_raw(Box::new(contents)) |
494 | } | |
041b39d2 | 495 | |
8faf50e0 XL |
496 | fn get(&mut self) -> &(dyn Any + Send) { |
497 | self.fill() | |
498 | } | |
499 | } | |
94b46f34 | 500 | |
29967ef6 XL |
501 | struct StrPanicPayload(&'static str); |
502 | ||
503 | unsafe impl BoxMeUp for StrPanicPayload { | |
504 | fn take_box(&mut self) -> *mut (dyn Any + Send) { | |
505 | Box::into_raw(Box::new(self.0)) | |
506 | } | |
507 | ||
508 | fn get(&mut self) -> &(dyn Any + Send) { | |
509 | &self.0 | |
510 | } | |
511 | } | |
512 | ||
94b46f34 XL |
513 | let loc = info.location().unwrap(); // The current implementation always returns Some |
514 | let msg = info.message().unwrap(); // The current implementation always returns Some | |
3dfed10e | 515 | crate::sys_common::backtrace::__rust_end_short_backtrace(move || { |
29967ef6 XL |
516 | if let Some(msg) = msg.as_str() { |
517 | rust_panic_with_hook(&mut StrPanicPayload(msg), info.message(), loc); | |
518 | } else { | |
519 | rust_panic_with_hook(&mut PanicPayload::new(msg), info.message(), loc); | |
520 | } | |
3dfed10e | 521 | }) |
94b46f34 XL |
522 | } |
523 | ||
60c5eb7d XL |
524 | /// This is the entry point of panicking for the non-format-string variants of |
525 | /// panic!() and assert!(). In particular, this is the only entry point that supports | |
526 | /// arbitrary payloads, not just format strings. | |
dfeec247 XL |
527 | #[unstable(feature = "libstd_sys_internals", reason = "used by the panic! macro", issue = "none")] |
528 | #[cfg_attr(not(test), lang = "begin_panic")] | |
529 | // lang item for CTFE panic support | |
a1dfa0c6 XL |
530 | // never inline unless panic_immediate_abort to avoid code |
531 | // bloat at the call sites as much as possible | |
dfeec247 | 532 | #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))] |
a1dfa0c6 | 533 | #[cold] |
dfeec247 | 534 | #[track_caller] |
74b04a01 | 535 | pub fn begin_panic<M: Any + Send>(msg: M) -> ! { |
a1dfa0c6 | 536 | if cfg!(feature = "panic_immediate_abort") { |
f035d41b | 537 | intrinsics::abort() |
a1dfa0c6 XL |
538 | } |
539 | ||
3dfed10e XL |
540 | let loc = Location::caller(); |
541 | return crate::sys_common::backtrace::__rust_end_short_backtrace(move || { | |
542 | rust_panic_with_hook(&mut PanicPayload::new(msg), None, loc) | |
543 | }); | |
83c7162d XL |
544 | |
545 | struct PanicPayload<A> { | |
546 | inner: Option<A>, | |
547 | } | |
548 | ||
549 | impl<A: Send + 'static> PanicPayload<A> { | |
550 | fn new(inner: A) -> PanicPayload<A> { | |
551 | PanicPayload { inner: Some(inner) } | |
552 | } | |
553 | } | |
554 | ||
555 | unsafe impl<A: Send + 'static> BoxMeUp for PanicPayload<A> { | |
60c5eb7d | 556 | fn take_box(&mut self) -> *mut (dyn Any + Send) { |
dfeec247 XL |
557 | // Note that this should be the only allocation performed in this code path. Currently |
558 | // this means that panic!() on OOM will invoke this code path, but then again we're not | |
559 | // really ready for panic on OOM anyway. If we do start doing this, then we should | |
560 | // propagate this allocation to be performed in the parent of this thread instead of the | |
561 | // thread that's panicking. | |
83c7162d | 562 | let data = match self.inner.take() { |
8faf50e0 | 563 | Some(a) => Box::new(a) as Box<dyn Any + Send>, |
60c5eb7d | 564 | None => process::abort(), |
83c7162d XL |
565 | }; |
566 | Box::into_raw(data) | |
567 | } | |
568 | ||
8faf50e0 | 569 | fn get(&mut self) -> &(dyn Any + Send) { |
83c7162d XL |
570 | match self.inner { |
571 | Some(ref a) => a, | |
60c5eb7d | 572 | None => process::abort(), |
83c7162d XL |
573 | } |
574 | } | |
575 | } | |
a7813a04 XL |
576 | } |
577 | ||
83c7162d | 578 | /// Central point for dispatching panics. |
a7813a04 | 579 | /// |
83c7162d XL |
580 | /// Executes the primary logic for a panic, including checking for recursive |
581 | /// panics, panic hooks, and finally dispatching to the panic runtime to either | |
582 | /// abort or unwind. | |
dfeec247 XL |
583 | fn rust_panic_with_hook( |
584 | payload: &mut dyn BoxMeUp, | |
585 | message: Option<&fmt::Arguments<'_>>, | |
586 | location: &Location<'_>, | |
587 | ) -> ! { | |
17df50a5 | 588 | let (must_abort, panics) = panic_count::increase(); |
a7813a04 | 589 | |
0731742a | 590 | // If this is the third nested call (e.g., panics == 2, this is 0-indexed), |
a7813a04 XL |
591 | // the panic hook probably triggered the last panic, otherwise the |
592 | // double-panic check would have aborted the process. In this case abort the | |
593 | // process real quickly as we don't want to try calling it again as it'll | |
594 | // probably just panic again. | |
17df50a5 XL |
595 | if must_abort || panics > 2 { |
596 | if panics > 2 { | |
597 | // Don't try to print the message in this case | |
598 | // - perhaps that is causing the recursive panics. | |
599 | rtprintpanic!("thread panicked while processing panic. aborting.\n"); | |
600 | } else { | |
601 | // Unfortunately, this does not print a backtrace, because creating | |
602 | // a `Backtrace` will allocate, which we must to avoid here. | |
603 | let panicinfo = PanicInfo::internal_constructor(message, location); | |
604 | rtprintpanic!("{}\npanicked after panic::always_abort(), aborting.\n", panicinfo); | |
605 | } | |
f035d41b | 606 | intrinsics::abort() |
b039eaaf SL |
607 | } |
608 | ||
9cc50fc6 | 609 | unsafe { |
dfeec247 | 610 | let mut info = PanicInfo::internal_constructor(message, location); |
17df50a5 | 611 | let _guard = HOOK_LOCK.read(); |
54a0048b | 612 | match HOOK { |
60c5eb7d | 613 | // Some platforms (like wasm) know that printing to stderr won't ever actually |
83c7162d | 614 | // print anything, and if that's the case we can skip the default |
60c5eb7d XL |
615 | // hook. Since string formatting happens lazily when calling `payload` |
616 | // methods, this means we avoid formatting the string at all! | |
617 | // (The panic runtime might still call `payload.take_box()` though and trigger | |
618 | // formatting.) | |
0731742a | 619 | Hook::Default if panic_output().is_none() => {} |
83c7162d XL |
620 | Hook::Default => { |
621 | info.set_payload(payload.get()); | |
622 | default_hook(&info); | |
623 | } | |
624 | Hook::Custom(ptr) => { | |
625 | info.set_payload(payload.get()); | |
626 | (*ptr)(&info); | |
627 | } | |
0731742a | 628 | }; |
9cc50fc6 | 629 | } |
b039eaaf | 630 | |
5bcae85e | 631 | if panics > 1 { |
b039eaaf SL |
632 | // If a thread panics while it's already unwinding then we |
633 | // have limited options. Currently our preference is to | |
634 | // just abort. In the future we may consider resuming | |
635 | // unwinding or otherwise exiting the thread cleanly. | |
17df50a5 | 636 | rtprintpanic!("thread panicked while panicking. aborting.\n"); |
f035d41b | 637 | intrinsics::abort() |
1a4d82fc | 638 | } |
a7813a04 | 639 | |
0531ce1d | 640 | rust_panic(payload) |
a7813a04 XL |
641 | } |
642 | ||
60c5eb7d XL |
643 | /// This is the entry point for `resume_unwind`. |
644 | /// It just forwards the payload to the panic runtime. | |
645 | pub fn rust_panic_without_hook(payload: Box<dyn Any + Send>) -> ! { | |
f035d41b | 646 | panic_count::increase(); |
83c7162d | 647 | |
8faf50e0 | 648 | struct RewrapBox(Box<dyn Any + Send>); |
83c7162d XL |
649 | |
650 | unsafe impl BoxMeUp for RewrapBox { | |
60c5eb7d | 651 | fn take_box(&mut self) -> *mut (dyn Any + Send) { |
83c7162d XL |
652 | Box::into_raw(mem::replace(&mut self.0, Box::new(()))) |
653 | } | |
654 | ||
8faf50e0 | 655 | fn get(&mut self) -> &(dyn Any + Send) { |
83c7162d XL |
656 | &*self.0 |
657 | } | |
658 | } | |
659 | ||
60c5eb7d | 660 | rust_panic(&mut RewrapBox(payload)) |
5bcae85e SL |
661 | } |
662 | ||
0bf4aa26 XL |
663 | /// An unmangled function (through `rustc_std_internal_symbol`) on which to slap |
664 | /// yer breakpoints. | |
665 | #[inline(never)] | |
666 | #[cfg_attr(not(test), rustc_std_internal_symbol)] | |
667 | fn rust_panic(mut msg: &mut dyn BoxMeUp) -> ! { | |
a7813a04 | 668 | let code = unsafe { |
8faf50e0 | 669 | let obj = &mut msg as *mut &mut dyn BoxMeUp; |
5869c6ff | 670 | __rust_start_panic(obj) |
a7813a04 XL |
671 | }; |
672 | rtabort!("failed to initiate panic, error {}", code) | |
1a4d82fc | 673 | } |