ErrorObjectCommon.cpp

//===--- ErrorObjectCommon.cpp - Recoverable error object -----------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This implements the parts of the standard Error protocol type which are
// shared between the ObjC-interoperable implementation and the native
// implementation. The parts specific to each implementation can be found in
// ErrorObject.mm (for the ObjC-interoperable parts) and ErrorObjectNative.cpp.
//
//===----------------------------------------------------------------------===//

#include "swift/Runtime/Concurrent.h"
#include "swift/Runtime/Config.h"
#include "ErrorObject.h"
#include "ErrorObjectTestSupport.h"

using namespace swift;

std::atomic<void (*)(SwiftError *error)> swift::_swift_willThrow;

void swift::_swift_setWillThrowHandler(void (* handler)(SwiftError *error)) {
  _swift_willThrow.store(handler, std::memory_order_release);
}

/// Breakpoint hook for debuggers that is called for untyped throws, and
/// calls _swift_willThrow if set.
SWIFT_CC(swift) void
swift::swift_willThrow(SWIFT_CONTEXT void *unused,
                       SWIFT_ERROR_RESULT SwiftError **error) {
  // Cheap check to bail out early, since we expect there to be no callbacks
  // the vast majority of the time.
  auto handler = _swift_willThrow.load(std::memory_order_acquire);
  if (SWIFT_UNLIKELY(handler)) {
    (* handler)(*error);
  }
}

std::atomic<void (*)(
  OpaqueValue *value,
  const Metadata *type,
  const WitnessTable *errorConformance
)> swift::_swift_willThrowTypedImpl;

/// Breakpoint hook for debuggers that is called for typed throws, and calls
/// _swift_willThrowTypedImpl if set. If not set and _swift_willThrow is set, this calls
/// that hook instead and implicitly boxes the typed error in an any Error for that call.
SWIFT_CC(swift) void
swift::swift_willThrowTypedImpl(OpaqueValue *value,
                                const Metadata *type,
                                const WitnessTable *errorConformance) {
  // Cheap check to bail out early, since we expect there to be no callbacks
  // the vast majority of the time.
  auto handler = _swift_willThrowTypedImpl.load(std::memory_order_acquire);
  if (SWIFT_UNLIKELY(handler)) {
    (* handler)(value, type, errorConformance);
  } else {
    auto fallbackHandler = _swift_willThrow.load(std::memory_order_acquire);
    if (SWIFT_UNLIKELY(fallbackHandler)) {
      // Form an error box containing the error.
      BoxPair boxedError = swift_allocError(
        type, errorConformance, value, /*isTake=*/false);

      // Hand the boxed error off to the handler.
      auto errorBox = reinterpret_cast<SwiftError *>(boxedError.object);
      (* fallbackHandler)(errorBox);

      // Release the error box.
      swift_errorRelease(errorBox);
    }
  }
}