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f5bdb858e0
Moved all the threading code to one place. Added explicit support for Darwin, Linux, Pthreads, C11 threads and Win32 threads, including new implementations of Once for Linux, Pthreads, C11 and Win32. rdar://90776105
110 lines
3.9 KiB
C++
110 lines
3.9 KiB
C++
//===--- ProtocolConformance.cpp - Swift protocol conformance checking ----===//
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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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// Checking and caching of Swift protocol conformances.
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//
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// This implementation is intended to be backward-deployed into Swift 5.0
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// runtimes.
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//
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//===----------------------------------------------------------------------===//
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#include "Overrides.h"
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#include "../../public/runtime/Private.h"
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#include "swift/Threading/Once.h"
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#include <dlfcn.h>
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#include <mach-o/dyld.h>
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#include <mach-o/getsect.h>
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#include <objc/runtime.h>
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using namespace swift;
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#if __POINTER_WIDTH__ == 64
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using mach_header_platform = mach_header_64;
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#else
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using mach_header_platform = mach_header;
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#endif
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/// The Mach-O section name for the section containing protocol conformances.
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/// This lives within SEG_TEXT.
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constexpr const char ProtocolConformancesSection[] = "__swift5_proto";
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// A dummy target context descriptor to use in conformance records which point
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// to a NULL descriptor. It doesn't have to be completely valid, just something
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// that code reading conformance descriptors will ignore.
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struct {
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ContextDescriptorFlags flags;
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int32_t offset;
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} DummyTargetContextDescriptor = {
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ContextDescriptorFlags().withKind(ContextDescriptorKind::Extension),
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0
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};
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// Search for any protocol conformance descriptors with a NULL type descriptor
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// and rewrite those to point to the dummy descriptor. This occurs when an
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// extension is used to declare a conformance on a weakly linked type and that
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// type is not present at runtime.
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static void addImageCallback(const mach_header *mh, intptr_t vmaddr_slide) {
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unsigned long size;
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const uint8_t *section =
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getsectiondata(reinterpret_cast<const mach_header_platform *>(mh),
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SEG_TEXT, ProtocolConformancesSection,
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&size);
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if (!section)
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return;
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auto recordsBegin
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= reinterpret_cast<const ProtocolConformanceRecord*>(section);
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auto recordsEnd
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= reinterpret_cast<const ProtocolConformanceRecord*>
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(section + size);
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for (auto record = recordsBegin; record != recordsEnd; ++record) {
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auto descriptor = record->get();
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if (auto typePtr = descriptor->_getTypeDescriptorLocation()) {
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if (*typePtr == nullptr)
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*typePtr = reinterpret_cast<TargetContextDescriptor<InProcess> *>(
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&DummyTargetContextDescriptor);
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}
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}
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}
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// Register the add image callback with dyld.
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static void registerAddImageCallback(void *) {
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_dyld_register_func_for_add_image(addImageCallback);
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}
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// Defined in libswiftCompatibility51, which is always linked if we link against
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// libswiftCompatibility50
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const Metadata *_swiftoverride_class_getSuperclass(const Metadata *theClass);
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const WitnessTable *
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swift::swift50override_conformsToProtocol(const Metadata *type,
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const ProtocolDescriptor *protocol,
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ConformsToProtocol_t *original_conformsToProtocol)
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{
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// Register our add image callback if necessary.
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static swift::once_t token;
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swift::once(token, registerAddImageCallback, nullptr);
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// The implementation of swift_conformsToProtocol in Swift 5.0 would return
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// a false negative answer when asking whether a subclass conforms using
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// a conformance from a superclass. Work around this by walking up the
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// superclass chain in cases where the original implementation returns
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// null.
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do {
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auto result = original_conformsToProtocol(type, protocol);
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if (result)
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return result;
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} while ((type = _swiftoverride_class_getSuperclass(type)));
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return nullptr;
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}
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