Commit 06d261daf62620e3449ba451898c7ad9ae750f41 | rust

author	bors <bors@rust-lang.org> 2024-10-17 04:34:51 UTC
committer	bors <bors@rust-lang.org> 2024-10-17 04:34:51 UTC
log	06d261daf62620e3449ba451898c7ad9ae750f41
tree	35b821155357b77c05b8bb049a9384b0f59addf1
parent	dd5127615ad626741a1116d022cf784637ac05df
parent	bb531083cc0301d2152dc59746eb30472564948d

Auto merge of #129582 - nbdd0121:unwind, r=nnethercote

Make destructors on `extern "C"` frames to be executed

This would make the example in #123231 print "Noisy Drop". I didn't mark this as fixing the issue because the behaviour is yet to be spec'ed.

Tracking:

- https://github.com/rust-lang/rust/issues/74990

8 files changed, 99 insertions(+), 17 deletions(-)

compiler/rustc_mir_transform/src/abort_unwinding_calls.rs+19-6

...	...	@@ -51,11 +51,20 @@ impl<'tcx> crate::MirPass<'tcx> for AbortUnwindingCalls {
51	51	// This will filter to functions with `extern "C-unwind"` ABIs, for
52	52	// example.
53	53	for block in body.basic_blocks.as_mut() {
	54	let Some(terminator) = &mut block.terminator else { continue };
	55	let span = terminator.source_info.span;
	56
	57	// If we see an `UnwindResume` terminator inside a function that cannot unwind, we need
	58	// to replace it with `UnwindTerminate`.
	59	if let TerminatorKind::UnwindResume = &terminator.kind
	60	&& !body_can_unwind
	61	{
	62	terminator.kind = TerminatorKind::UnwindTerminate(UnwindTerminateReason::Abi);
	63	}
	64
54	65	if block.is_cleanup {
55	66	continue;
56	67	}
57		let Some(terminator) = &block.terminator else { continue };
58		let span = terminator.source_info.span;
59	68
60	69	let call_can_unwind = match &terminator.kind {
61	70	TerminatorKind::Call { func, .. } => {
...	...	@@ -87,14 +96,18 @@ impl<'tcx> crate::MirPass<'tcx> for AbortUnwindingCalls {
87	96	if !call_can_unwind {
88	97	// If this function call can't unwind, then there's no need for it
89	98	// to have a landing pad. This means that we can remove any cleanup
90		// registered for it.
	99	// registered for it (and turn it into `UnwindAction::Unreachable`).
91	100	let cleanup = block.terminator_mut().unwind_mut().unwrap();
92	101	*cleanup = UnwindAction::Unreachable;
93		} else if !body_can_unwind {
	102	} else if !body_can_unwind
	103	&& matches!(terminator.unwind(), Some(UnwindAction::Continue))
	104	{
94	105	// Otherwise if this function can unwind, then if the outer function
95	106	// can also unwind there's nothing to do. If the outer function
96		// can't unwind, however, we need to change the landing pad for this
97		// function call to one that aborts.
	107	// can't unwind, however, we need to ensure that any `UnwindAction::Continue`
	108	// is replaced with terminate. For those with `UnwindAction::Cleanup`,
	109	// cleanup will still happen, and terminate will happen afterwards handled by
	110	// the `UnwindResume` -> `UnwindTerminate` terminator replacement.
98	111	let cleanup = block.terminator_mut().unwind_mut().unwrap();
99	112	*cleanup = UnwindAction::Terminate(UnwindTerminateReason::Abi);
100	113	}

tests/mir-opt/asm_unwind_panic_abort.main.AbortUnwindingCalls.after.mir+5-1

...	...	@@ -7,7 +7,7 @@ fn main() -> () {
7	7	bb0: {
8	8	StorageLive(_1);
9	9	_1 = const ();
10		asm!("", options(MAY_UNWIND)) -> [return: bb1, unwind terminate(abi)];
	10	asm!("", options(MAY_UNWIND)) -> [return: bb1, unwind: bb2];
11	11	}
12	12
13	13	bb1: {
...	...	@@ -15,4 +15,8 @@ fn main() -> () {
15	15	_0 = const ();
16	16	return;
17	17	}
	18
	19	bb2 (cleanup): {
	20	terminate(abi);
	21	}
18	22	}

tests/mir-opt/asm_unwind_panic_abort.rs+3-1

...	...	@@ -10,7 +10,9 @@
10	10	fn main() {
11	11	// CHECK-LABEL: fn main(
12	12	// CHECK: asm!(
13		// CHECK-SAME: unwind terminate(abi)
	13	// CHECK-SAME: unwind: [[unwind:bb.*]]]
	14	// CHECK: [[unwind]] (cleanup)
	15	// CHECK-NEXT: terminate(abi)
14	16	unsafe {
15	17	std::arch::asm!("", options(may_unwind));
16	18	}

tests/mir-opt/c_unwind_terminate.rs created+25

...	...	@@ -0,0 +1,25 @@
	1	//@ needs-unwind
	2
	3	struct Noise;
	4	impl Drop for Noise {
	5	fn drop(&mut self) {
	6	eprintln!("Noisy Drop");
	7	}
	8	}
	9
	10	fn panic() {
	11	panic!();
	12	}
	13
	14	// EMIT_MIR c_unwind_terminate.test.AbortUnwindingCalls.after.mir
	15	extern "C" fn test() {
	16	// CHECK-LABEL: fn test(
	17	// CHECK: drop
	18	// CHECK-SAME: unwind: [[unwind:bb.*]]]
	19	// CHECK: [[unwind]] (cleanup)
	20	// CHECK-NEXT: terminate(abi)
	21	let _val = Noise;
	22	panic();
	23	}
	24
	25	fn main() {}

tests/mir-opt/c_unwind_terminate.test.AbortUnwindingCalls.after.mir created+36

...	...	@@ -0,0 +1,36 @@
	1	// MIR for `test` after AbortUnwindingCalls
	2
	3	fn test() -> () {
	4	let mut _0: ();
	5	let _1: Noise;
	6	let _2: ();
	7	scope 1 {
	8	debug _val => _1;
	9	}
	10
	11	bb0: {
	12	StorageLive(_1);
	13	_1 = Noise;
	14	StorageLive(_2);
	15	_2 = panic() -> [return: bb1, unwind: bb3];
	16	}
	17
	18	bb1: {
	19	StorageDead(_2);
	20	_0 = const ();
	21	drop(_1) -> [return: bb2, unwind: bb4];
	22	}
	23
	24	bb2: {
	25	StorageDead(_1);
	26	return;
	27	}
	28
	29	bb3 (cleanup): {
	30	drop(_1) -> [return: bb4, unwind terminate(cleanup)];
	31	}
	32
	33	bb4 (cleanup): {
	34	terminate(abi);
	35	}
	36	}

tests/run-make/longjmp-across-rust/main.rs-8

...	...	@@ -10,19 +10,11 @@ fn main() {
10	10	}
11	11	}
12	12
13		struct A;
14
15		impl Drop for A {
16		fn drop(&mut self) {}
17		}
18
19	13	extern "C" fn test_middle() {
20		let _a = A;
21	14	foo();
22	15	}
23	16
24	17	fn foo() {
25		let _a = A;
26	18	unsafe {
27	19	test_end();
28	20	}

tests/ui/panics/panic-in-ffi.rs+9

...	...	@@ -2,13 +2,22 @@
2	2	//@ exec-env:RUST_BACKTRACE=0
3	3	//@ check-run-results
4	4	//@ error-pattern: panic in a function that cannot unwind
	5	//@ error-pattern: Noisy Drop
5	6	//@ normalize-stderr-test: "\n +[0-9]+:[^\n]+" -> ""
6	7	//@ normalize-stderr-test: "\n +at [^\n]+" -> ""
7	8	//@ normalize-stderr-test: "(core/src/panicking\.rs):[0-9]+:[0-9]+" -> "$1:$$LINE:$$COL"
8	9	//@ needs-unwind
9	10	//@ ignore-emscripten "RuntimeError" junk in output
10	11
	12	struct Noise;
	13	impl Drop for Noise {
	14	fn drop(&mut self) {
	15	eprintln!("Noisy Drop");
	16	}
	17	}
	18
11	19	extern "C" fn panic_in_ffi() {
	20	let _val = Noise;
12	21	panic!("Test");
13	22	}
14	23

tests/ui/panics/panic-in-ffi.run.stderr+2-1

...	...	@@ -1,6 +1,7 @@
1		thread 'main' panicked at $DIR/panic-in-ffi.rs:12:5:
	1	thread 'main' panicked at $DIR/panic-in-ffi.rs:21:5:
2	2	Test
3	3	note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
	4	Noisy Drop
4	5	thread 'main' panicked at core/src/panicking.rs:$LINE:$COL:
5	6	panic in a function that cannot unwind
6	7	stack backtrace: