mirror of
https://github.com/apple/swift.git
synced 2025-12-14 20:36:38 +01:00
110 lines
3.9 KiB
C++
110 lines
3.9 KiB
C++
//===--- ProtocolConformance.cpp - Swift protocol conformance checking ----===//
|
|
//
|
|
// This source file is part of the Swift.org open source project
|
|
//
|
|
// Copyright (c) 2014 - 2017 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
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// Checking and caching of Swift protocol conformances.
|
|
//
|
|
// This implementation is intended to be backward-deployed into Swift 5.0
|
|
// runtimes.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "Overrides.h"
|
|
#include "../../public/runtime/Private.h"
|
|
#include "swift/Basic/Lazy.h"
|
|
#include <dlfcn.h>
|
|
#include <mach-o/dyld.h>
|
|
#include <mach-o/getsect.h>
|
|
#include <objc/runtime.h>
|
|
|
|
using namespace swift;
|
|
|
|
#if __POINTER_WIDTH__ == 64
|
|
using mach_header_platform = mach_header_64;
|
|
#else
|
|
using mach_header_platform = mach_header;
|
|
#endif
|
|
|
|
/// The Mach-O section name for the section containing protocol conformances.
|
|
/// This lives within SEG_TEXT.
|
|
constexpr const char ProtocolConformancesSection[] = "__swift5_proto";
|
|
|
|
// A dummy target context descriptor to use in conformance records which point
|
|
// to a NULL descriptor. It doesn't have to be completely valid, just something
|
|
// that code reading conformance descriptors will ignore.
|
|
struct {
|
|
ContextDescriptorFlags flags;
|
|
int32_t offset;
|
|
} DummyTargetContextDescriptor = {
|
|
ContextDescriptorFlags().withKind(ContextDescriptorKind::Extension),
|
|
0
|
|
};
|
|
|
|
// Search for any protocol conformance descriptors with a NULL type descriptor
|
|
// and rewrite those to point to the dummy descriptor. This occurs when an
|
|
// extension is used to declare a conformance on a weakly linked type and that
|
|
// type is not present at runtime.
|
|
static void addImageCallback(const mach_header *mh, intptr_t vmaddr_slide) {
|
|
unsigned long size;
|
|
const uint8_t *section =
|
|
getsectiondata(reinterpret_cast<const mach_header_platform *>(mh),
|
|
SEG_TEXT, ProtocolConformancesSection,
|
|
&size);
|
|
if (!section)
|
|
return;
|
|
|
|
auto recordsBegin
|
|
= reinterpret_cast<const ProtocolConformanceRecord*>(section);
|
|
auto recordsEnd
|
|
= reinterpret_cast<const ProtocolConformanceRecord*>
|
|
(section + size);
|
|
for (auto record = recordsBegin; record != recordsEnd; ++record) {
|
|
auto descriptor = record->get();
|
|
if (auto typePtr = descriptor->_getTypeDescriptorLocation()) {
|
|
if (*typePtr == nullptr)
|
|
*typePtr = reinterpret_cast<TargetContextDescriptor<InProcess> *>(
|
|
&DummyTargetContextDescriptor);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Register the add image callback with dyld.
|
|
static void registerAddImageCallback(void *) {
|
|
_dyld_register_func_for_add_image(addImageCallback);
|
|
}
|
|
|
|
// Defined in libswiftCompatibility51, which is always linked if we link against
|
|
// libswiftCompatibility50
|
|
const Metadata *_swiftoverride_class_getSuperclass(const Metadata *theClass);
|
|
|
|
const WitnessTable *
|
|
swift::swift50override_conformsToProtocol(const Metadata *type,
|
|
const ProtocolDescriptor *protocol,
|
|
ConformsToProtocol_t *original_conformsToProtocol)
|
|
{
|
|
// Register our add image callback if necessary.
|
|
static OnceToken_t token;
|
|
SWIFT_ONCE_F(token, registerAddImageCallback, nullptr);
|
|
|
|
// The implementation of swift_conformsToProtocol in Swift 5.0 would return
|
|
// a false negative answer when asking whether a subclass conforms using
|
|
// a conformance from a superclass. Work around this by walking up the
|
|
// superclass chain in cases where the original implementation returns
|
|
// null.
|
|
do {
|
|
auto result = original_conformsToProtocol(type, protocol);
|
|
if (result)
|
|
return result;
|
|
} while ((type = _swiftoverride_class_getSuperclass(type)));
|
|
|
|
return nullptr;
|
|
}
|