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3fa07a0e7a
`swift_willThrow` is called with an error right before it is thrown. This existing entrypoint requires an already-boxed error existential; with typed errors, we don't have the error existential on hand, so we would need to allocate the box to throw a typed error. That's not okay. Introduce a new `swift_willThrowTypedImpl` entry point into the runtime that will first check for the presence of an error handler and, if one is present, box the error to provide to the error handler. This maintains the no-allocations path for typed errors while still allowing existing error handlers to work. This new entrypoint isn't available on older Swift runtimes, so create a back-deployable shim called by the compiler. On new-enough platforms, this will call through to `swift_willThrowTypedImpl`. On older platforms, we drop the error and don't call the registered will-throw handler at all. This is a compromise that avoids boxing when throwing typed errors, at the cost of a slightly different experience for this new feature on older runtimes. Fixes rdar://119828459.
104 lines
3.7 KiB
C++
104 lines
3.7 KiB
C++
//===--- Error.h - Swift Runtime ABI for error values -----------*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// Swift runtime support for working with error values.
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//
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// The ABI here is quite different in ObjC and non-ObjC modes.
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// In ObjC mode, SwiftError is closely related to the NSError class:
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// native errors are boxed as a subclass of NSError, but non-native
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// errors may simply be NSError objects directly from Objective-C.
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// In non-ObjC mode, SwiftError boxes are always native.
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//
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//===----------------------------------------------------------------------===//
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#ifndef SWIFT_RUNTIME_ERROR_H
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#define SWIFT_RUNTIME_ERROR_H
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#include "swift/Runtime/HeapObject.h"
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#include "swift/Runtime/Metadata.h"
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namespace swift {
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struct SwiftError;
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/// Allocate a catchable error object.
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///
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/// If value is nonnull, it should point to a value of \c type, which will be
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/// copied (or taken if \c isTake is true) into the newly-allocated error box.
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/// If value is null, the box's contents will be left uninitialized, and
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/// \c isTake should be false.
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SWIFT_CC(swift) SWIFT_RUNTIME_STDLIB_API
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BoxPair swift_allocError(const Metadata *type,
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const WitnessTable *errorConformance,
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OpaqueValue *value, bool isTake);
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/// Deallocate an error object whose contained object has already been
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/// destroyed.
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SWIFT_RUNTIME_STDLIB_API
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void swift_deallocError(SwiftError *error, const Metadata *type);
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struct ErrorValueResult {
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const OpaqueValue *value;
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const Metadata *type;
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const WitnessTable *errorConformance;
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};
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/// Extract a pointer to the value, the type metadata, and the Error
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/// protocol witness from an error object.
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///
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/// The "scratch" pointer should point to an uninitialized word-sized
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/// temporary buffer. The implementation may write a reference to itself to
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/// that buffer if the error object is a toll-free-bridged NSError instead of
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/// a native Swift error, in which case the object itself is the "boxed" value.
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SWIFT_RUNTIME_STDLIB_API
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void swift_getErrorValue(const SwiftError *errorObject,
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void **scratch,
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ErrorValueResult *out);
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/// Called when throwing an error. Serves as a breakpoint hook
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/// for debuggers.
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SWIFT_CC(swift)
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SWIFT_RUNTIME_STDLIB_API void
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swift_willThrow(SWIFT_CONTEXT void *unused,
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SWIFT_ERROR_RESULT SwiftError **object);
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/// Called when throwing a typed error. Serves as a breakpoint hook
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/// for debuggers.
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SWIFT_CC(swift)
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SWIFT_RUNTIME_STDLIB_API void
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swift_willThrowTypedImpl(OpaqueValue *value,
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const Metadata *type,
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const WitnessTable *errorConformance);
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/// Called when an error is thrown out of the top level of a script.
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SWIFT_CC(swift)
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SWIFT_RUNTIME_STDLIB_API SWIFT_NORETURN void
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swift_errorInMain(SwiftError *object);
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/// Called when the try! operator fails.
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SWIFT_CC(swift)
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SWIFT_RUNTIME_STDLIB_API SWIFT_NORETURN void
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swift_unexpectedError(SwiftError *object, OpaqueValue *filenameStart,
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long filenameLength, bool isAscii, unsigned long line);
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/// Retain an error box.
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SWIFT_RUNTIME_STDLIB_API
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SwiftError *swift_errorRetain(SwiftError *object);
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/// Release an error box.
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SWIFT_RUNTIME_STDLIB_API
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void swift_errorRelease(SwiftError *object);
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} // end namespace swift
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#endif
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