Fix asyncMainDrainQueue noreturn warning #61692
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
@swift-ci please test |
|
macOS: Linux: Windows: |
etcwilde
force-pushed
the
ewilde/fix-noreturn-warning
branch
from
b931348 to
d635a2d
Compare
|
@swift-ci please test |
|
Linux: Windows: |
The async main drain queue function is noreturn, but was emitting a warning due to the override compatibility returning the result of the overridden function in the wrapper override function. To work around this, I've added the `OVERRIDE_TASK_NORETURN` macro, which provides an override point for noreturn functions in the concurrency library that doesn't return the result from the wrapped function, avoiding the warning. In the event that the function is not set, the macro is set to the normal `OVERRIDE` with the return type set to `void`.
etcwilde
force-pushed
the
ewilde/fix-noreturn-warning
branch
from
d635a2d to
ec7a926
Compare
The swift_task_asyncMainDrainQueue function acts as the entrypoint into driving the main queues, ultimately running the whole program and acting as the backing driver of the main actor. Making the function hookable means that custom concurrency runtimes can implement their own async entrypoints, allowing async top-level code and async-main to "just work".
This patch tests that the hook actually works. Not going to lie, the test is pretty disgusting. The function we're testing is a noreturn function, which introduces some interesting challenges when we need to return to finish the test. I need to somehow exit the function without killing the process, but also without returning. If I just use a loop properly, the test will hang for the age of the universe. If I don't and return from the hook, the test will abort or crash. I tried removing the abort after the hook in the hook override macro to see if we could sneak past the compiler, and no, that explodes on the return pointer. So, here's the workaround. C++11 threads don't seem to have a way to kill themselves, but you can use `pthread_exit` or `pthread_kill` to either kill yourself or kill another thread. So the override function sets the `Ran` to true, and then exits (which is noreturn, so we haven't broken that contract), killing itself and allowing us to join without returning from the inferior. The main thread immediately waits for the original thread to die. Since it blocks, we avoid the possible race on setting the state of `Ran` in the override hook and where it gets checked in the test. If that becomes an issue, we could probably just wrap the `Ran` bool in an atomic and call it a day. Anyway, it's well past my bedtime and I'm playing with threads. This can only end in a creative disaster. :D
|
@swift-ci please test |
|
@mikeash I had some fun writing that test. Turns out it's pretty tricky testing a |
|
I don't think I have any better ideas. You could get out of it by throwing an exception, but I don't think that qualifies as "better." |
|
macOS failure: Not my fault this time. |
|
@swift-ci please test macOS |
|
macOS failure should be fixed by: #64029 |
|
@swift-ci please test macOS |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The async main drain queue function is noreturn, but was emitting a warning due to the override compatibility returning the result of the overridden function in the wrapper override function. To work around this, I've added the
OVERRIDE_TASK_NORETURNmacro, which provides an override point for noreturn functions in the concurrency library that doesn't return the result from the wrapped function, avoiding the warning. In the event that the function is not set, the macro is set to the normalOVERRIDEwith the return type set tovoid.rdar://85521851