Tailored error reporting when dynamic casts have nonsensical type args #75151
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This inserts a suitably named function into the stack trace whenever a dynamic cast failure involves a NULL source or target type. Very often, crash logs include backtraces with function names but no log output; with this change, such a backtrace might look like the following -- note `TARGET_TYPE_NULL` in the function name here to mark the missing type information: ``` frame #0: __pthread_kill + 8 frame swiftlang#1: pthread_kill + 288 frame swiftlang#2: abort + 128 frame swiftlang#3: swift::fatalErrorv() frame swiftlang#4: swift::fatalError() frame swiftlang#5: swift_dynamicCastFailure_TARGET_TYPE_NULL() frame swiftlang#6: swift::swift_dynamicCastFailure() frame swiftlang#7: ::swift_dynamicCast() ``` Resolves rdar://130630157
mikeash
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Jul 11, 2024
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mikeash
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Lovely. There are probably a bunch more places where we should adopt this technique.
I'm worried about the compiler getting too clever for us and emitting fatalError as a tail call. The std::string destructor at the end of scope might prevent this, but on the other hand the noreturn attribute on fatalError might prevent that. We could annotate fatalError with __attribute__((not_tail_called)) or annotate these functions with __attribute__((disable_tail_calls)). The former would apply to all callers, but that might be a good thing.
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@swift-ci Please test |
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Cool!! |
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This inserts a suitably named function into the stack trace whenever a dynamic cast failure involves a NULL source or target type. Very often, crash logs include backtraces with function names but no log output; with this change, such a backtrace might look like the following -- note
TARGET_TYPE_NULLin the function name here to mark the missing type information:Resolves rdar://130630157