[SR-13247] Crash when using enum case as protocol witness #55687
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Comment by Stephen Emery Cotner (JIRA) Thanks very much for reporting this bug, Suyash. I'm glad my Evaluating experiment is making the rounds! I'm afraid there might be important context missing, though. Here is the complete example I originally posted on Twitter (cleaned up a little), which will crash in a playground. There are two essential things to notice:
This results in the error: error: Execution was interrupted, reason: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0).
The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.Here's the code: protocol Evaluating {
associatedtype Action: EvaluatorAction
func evaluate(_ action: Action)
}
protocol EvaluatorAction {}
protocol Evaluating_TextField: Evaluating where Action: Action_TextField {}
protocol Action_TextField: EvaluatorAction {
static func textFieldDidChange(text: String) -> Self
}
class Evaluator: Evaluating, Evaluating_TextField {
enum Action: Action_TextField {
case textFieldDidChange(text: String)
}
func evaluate(_ action: Action) {
switch action {
case .textFieldDidChange(let text):
print("text: \(text)")
}
}
}
struct SomethingLikeAView<E: Evaluating_TextField> {
let evaluator: E
init(evaluator: E) {
self.evaluator = evaluator
}
func type() {
let string: String = "thioahsdlfkjds lfjoidsjflkjds flkjds lkf aslkjfldsjf lkjsd flkjsd fl;kjsd a;fklj asdfkljdsa"
evaluator.evaluate(.textFieldDidChange(text: "\(string)")) // note: this is "\(string)", not the string itself
}
}
let evaluator = Evaluator()
let view = SomethingLikeAView(evaluator: evaluator)
view.type()I'm not very knowledgeable about heap allocations, but as far as I can tell, the string is freed from the heap as soon as it's added. When it comes time to print out the interpolated string, it's already gone. This problem does not happen if an evaluator is referred to by its concrete type. For instance, if you replace the line: struct SomethingLikeAView<E: Evaluating_TextField> {with: struct SomethingLikeAView<E: Evaluator> {then there is no crash. It is only when the evaluator is known by a protocol — when an enum case is really acting as a protocol witness — that we see this problem. |
AnthonyLatsis
added
the
crash
Environment
Swift version 5.3-dev (LLVM 9437a19, Swift d2f131f)
Target: x86_64-apple-darwin19.5.0
Additional Detail from JIRA
md5: d642963c32dd1a1d81246575bc705fa7
relates to:
Issue Description:
The following causes a segmentation fault when running:
When running in JIT, you get the following message:
Strangely, renaming some things fixes the crash. For example, if you rename
Evaluatingto something that has less characters, likePthen it doesn't crash.The text was updated successfully, but these errors were encountered: