Ask Foundation to capture NSError/CFError backtraces for us.
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On Apple platforms, when an error occurs in an Objective-C method or C function, convention is to return the error as an instance of `NSError`/`CFError` via an out-parameter. When that Objective-C method or C function is called by a Swift function, the Swift function detects the error, then effectively rethrows it, at which point our `swift_willThrow` hook is triggered. This can obscure the real origin of the error which may be many stack frames down from the point Swift takes over. This PR asks Foundation, via a relatively new internal function, to capture backtraces for instances of `NSError` and `CFError` at the point they are created. Then, when Swift Testing attempts to look up the backtrace for an error it has caught, if Foundation has generated one, then Swift Testing can substitute it in place of the one it generated in the `swift_willThrow` hook. Resolves rdar://114386243.
grynspan
added
enhancement
grynspan
requested review from
stmontgomery,
dennisweissmann,
briancroom,
SeanROlszewski and
suzannaratcliff
as code owners
stmontgomery
reviewed
Sep 9, 2024
stmontgomery
reviewed
Sep 9, 2024
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@swift-ci test |
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@swift-ci test |
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On Apple platforms, when an error occurs in an Objective-C method or C function, convention is to return the error as an instance of
NSError/CFErrorvia an out-parameter. When that Objective-C method or C function is called by a Swift function, the Swift function detects the error, then effectively rethrows it, at which point ourswift_willThrowhook is triggered. This can obscure the real origin of the error which may be many stack frames down from the point Swift takes over.This PR asks Foundation, via a relatively new internal function, to capture backtraces for instances of
NSErrorandCFErrorat the point they are created. Then, when Swift Testing attempts to look up the backtrace for an error it has caught, if Foundation has generated one, then Swift Testing can substitute it in place of the one it generated in theswift_willThrowhook.Resolves rdar://114386243.
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