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a52f2b9617
The main contribution of this CL is unification of disparate
handling of various functions like `Future.timeout`,
`Future.wait`, `_SuspendState.createAsyncCallbacks` and
`_SuspendState._createAsyncStarCallback` into a single
`@pragma('vm:awaiter-link')` which allows Dart developers
to specify where awaiter unwinder should look for the next
awaiter.
For example this allows unwinding to succeed for the code like this:
Future<int> outer(Future<int> inner) {
@pragma('vm:awaiter-link')
final completer = Completer<int>();
inner.then((v) => completer.complete(v));
return completer.future;
}
This refactoring also ensures that we preserve information
(including Function & Code objects) required for awaiter
unwinding across all modes (JIT, AOT and AOT with DWARF stack
traces). This guarantees users will get the same information
no matter which mode they are running in. Previously
we have been disabling awaiter_stacks tests in some AOT
modes - which led to regressions in the quality of produced
stacks.
This CL also cleans up relationship between debugger and awaiter
stack returned by StackTrace.current - which makes stack trace
displayed by debugger (used for stepping out and determinining
whether exception is caught or not) and `StackTrace.current`
consistent.
Finally we make one user visible change to the stack trace:
awaiter stack will no always include intermediate listeners
created through `Future.then`. Previously we would sometimes
include these listeners at the tail of the stack trace,
which was inconsistent.
Ultimately this means that code like this:
Future<int> inner() async {
await null; // asynchronous gap
print(StackTrace.current); // (*)
return 0;
}
Future<int> outer() async {
int process(int v) {
return v + 1;
}
return await inner().then(process);
}
void main() async {
await outer();
}
Produces stack trace like this:
inner
<asynchronous suspension>
outer.process
<asynchronous suspension>
outer
<asynchronous suspension>
main
<asynchronous suspension>
And when stepping out of `inner` execution will stop at `outer.process`
first and the next step out will bring execution to `outer` next.
Fixes https://github.com/dart-lang/sdk/issues/52797
Fixes https://github.com/dart-lang/sdk/issues/52203
Issue https://github.com/dart-lang/sdk/issues/47985
TEST=ci
Bug: b/279929839
CoreLibraryReviewExempt: CL just adds @pragma to facilitate unwinding
Cq-Include-Trybots: luci.dart.try:vm-aot-linux-product-x64-try,vm-aot-linux-debug-x64-try,vm-aot-linux-release-x64-try,vm-aot-obfuscate-linux-release-x64-try,vm-aot-dwarf-linux-product-x64-try
Change-Id: If377d5329d6a11c86effb9369dc603a7ae616fe7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/311680
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Commit-Queue: Slava Egorov <vegorov@google.com>
68 lines
2.2 KiB
C++
68 lines
2.2 KiB
C++
// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#ifndef RUNTIME_VM_STACK_TRACE_H_
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#define RUNTIME_VM_STACK_TRACE_H_
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#include <functional>
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#include "vm/allocation.h"
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#include "vm/flag_list.h"
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#include "vm/object.h"
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#include "vm/symbols.h"
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namespace dart {
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class StackTraceUtils : public AllStatic {
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public:
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static constexpr uword kFutureListenerPcOffset = 1;
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struct Frame {
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// Corresponding on stack frame or |nullptr| if this is an awaiter frame
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// or a gap.
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StackFrame* frame;
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// Code object corresponding to this frame.
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const Code& code;
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// Offset into the code object corresponding to this frame.
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//
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// Will be set to |kFutureListenerPcOffset| if this frame corresponds to
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// future listener that is not yet executing.
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uword pc_offset;
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// Closure corresponding to the awaiter frame or |null| if this is
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// a synchronous frame or a gap.
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const Closure& closure;
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// |true| if an asynchronous exception would be caught by a |catchError|
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// listener somewhere between the previous frame and this frame.
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bool has_async_catch_error;
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};
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// Returns |true| if this function is needed to correctly unwind through
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// awaiter chains. This means AOT compiler should retain |Function| object,
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// its signature and the corresponding |Code| object (so that we could
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// perform the reverse lookup).
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static bool IsNeededForAsyncAwareUnwinding(const Function& function);
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/// Collects all frames on the current stack until an async/async* frame is
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/// hit which has yielded before (i.e. is not in sync-async case).
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///
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/// From there on finds the closure of the async/async* frame and starts
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/// traversing the listeners.
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static void CollectFrames(
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Thread* thread,
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int skip_frames,
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const std::function<void(const Frame&)>& handle_frame);
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// If |closure| has an awaiter-link pointing to the |SuspendState|
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// the return that object.
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static bool GetSuspendState(const Closure& closure, Object* suspend_state);
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};
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} // namespace dart
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#endif // RUNTIME_VM_STACK_TRACE_H_
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