Tests: Add integration tests for @_backDeploy.

test/attr/Inputs/BackDeployHelper.swift

@@ -0,0 +1,195 @@
+
+/// Returns the dsohandle for the dynamic library.
+public func libraryHandle() -> UnsafeRawPointer {
+  return #dsohandle
+}
+
+/// Prepends "client:" or "library:" to the given string (depending on whether
+/// the dsohandle belongs to the library or not) and then prints it.
+public func testPrint(handle: UnsafeRawPointer, _ string: String) {
+  let libraryHandle = #dsohandle
+  let prefix = (handle == libraryHandle) ? "library" : "client"
+  print("\(prefix): \(string)")
+}
+
+/// Returns true if the host OS version is BackDeploy 2.0 or later, indicating
+/// that APIs back deployed before 2.0 should run in the library.
+public func isV2OrLater() -> Bool {
+  if #available(BackDeploy 2.0, *) {
+    return true
+  } else {
+    return false
+  }
+}
+
+/// Returns true if BackDeploy 2.0 APIs have been stripped from the binary.
+public func v2APIsAreStripped() -> Bool {
+#if STRIP_V2_APIS
+  return true
+#else
+  return false
+#endif // STRIP_V2_APIS
+}
+
+public enum BadError: Error, Equatable {
+  /// Indicates badness
+  case bad
+}
+
+/// A totally unnecessary wrapper for `Int` that adds mutability.
+public struct MutableInt {
+  @usableFromInline
+  internal var _value: Int
+
+  public init(_ value: Int) { _value = value }
+}
+
+/// A totally unnecessary wrapper for `Int` that provides reference semantics.
+public class ReferenceInt {
+  @usableFromInline
+  internal var _value: Int
+
+  public init(_ value: Int) { _value = value }
+}
+
+/// Describes types that can be incremented.
+public protocol Incrementable {
+  associatedtype Operand
+
+  mutating func incrementByOne() -> String
+  mutating func increment(by amount: Operand) -> Operand
+}
+
+extension MutableInt: Incrementable {
+  public mutating func incrementByOne() -> String {
+    _value += 1
+    return String(_value)
+  }
+
+  public mutating func increment(by amount: Int) -> Int {
+    _value += amount
+    return _value
+  }
+}
+
+extension ReferenceInt: Incrementable {
+  public func incrementByOne() -> String {
+    _value += 1
+    return String(_value)
+  }
+
+  public func increment(by amount: Int) -> Int {
+    _value += amount
+    return _value
+  }
+}
+
+extension Int {
+  @usableFromInline internal func byte(at index: Int) -> UInt8 {
+    UInt8(truncatingIfNeeded: self >> (index * 8))
+  }
+}
+
+// MARK: - Back deployed APIs
+
+#if !STRIP_V2_APIS
+
+@available(BackDeploy 1.0, *)
+@_backDeploy(BackDeploy 2.0)
+public func trivial() {
+  testPrint(handle: #dsohandle, "trivial")
+}
+
+@available(BackDeploy 1.0, *)
+@_backDeploy(BackDeploy 2.0)
+public func pleaseThrow(_ shouldThrow: Bool) throws -> Bool {
+  if shouldThrow { throw BadError.bad }
+  return !shouldThrow
+}
+
+@available(BackDeploy 1.0, *)
+@_backDeploy(BackDeploy 2.0)
+public func genericIncrement<T: Incrementable>(
+  _ x: inout T,
+  by amount: T.Operand
+) -> T.Operand {
+  return x.increment(by: amount)
+}
+
+@available(BackDeploy 1.0, *)
+@_backDeploy(BackDeploy 2.0)
+public func existentialIncrementByOne(_ x: inout any Incrementable) {
+  testPrint(handle: #dsohandle, x.incrementByOne())
+}
+
+extension MutableInt {
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public var value: Int { _value }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public func print() {
+    // Tests recursive @_backDeploy since `value` is also @_backDeploy
+    testPrint(handle: #dsohandle, String(value))
+  }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public static var zero: Self { MutableInt(0) }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public mutating func decrement(by amount: Int) -> Int {
+    _value -= amount
+    return _value
+  }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public func toIncrementable() -> any Incrementable { self }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public subscript(byteAt index: Int) -> UInt8 { _value.byte(at: index) }
+}
+
+extension ReferenceInt {
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public final var value: Int { _value }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public final func print() {
+    // Tests recursive use of back deployed APIs, since `value` is also
+    testPrint(handle: #dsohandle, String(value))
+  }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public final func copy() -> ReferenceInt {
+    return ReferenceInt(value)
+  }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public final class var zero: ReferenceInt { ReferenceInt(0) }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public final func decrement(by amount: Int) -> Int {
+    _value -= amount
+    return _value
+  }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public final func toIncrementable() -> any Incrementable { self }
+
+  @available(BackDeploy 1.0, *)
+  @_backDeploy(BackDeploy 2.0)
+  public final subscript(byteAt index: Int) -> UInt8 { _value.byte(at: index) }
+}
+
+#endif // !STRIP_V2_APIS

test/attr/attr_backDeploy_evolution.swift

@@ -0,0 +1,190 @@
+//
+// At a high level, this test is designed to verify that use of declarations
+// annotated with @_backDeploy behave as expected when running a client binary
+// on an older OS that does not have the back deployed APIs. The
+// BackDeployHelper framework has a number of APIs that are available in the
+// OSes identified by the "BackDeploy 1.0" availability macro and are back
+// deployed before OSes identified "BackDeploy 2.0". Verification is performed
+// the following way:
+//
+//  1. Build the helper framework with both BackDeploy 1.0 defined to an
+//     OS version before Swift ABI stability and 2.0 defined to an OS version
+//     after Swift ABI stability. Note that stradling ABI stability is not
+//     a necessary requirement of this test; it's just convenient to use OS
+//     versions that correspond to existing lit substitutions.
+//  2. Build the client executable with a deployment target set to the same
+//     OS version as BackDeploy 2.0.
+//  3. Run the client executable, verifying that the copies of the functions in
+//     the framework are used (verified by runtime logic using #dsohandle).
+//  4. Build a new copy of the helper framework, this time with BackDeploy 2.0
+//     set to a distant future OS version.
+//  5. Build a new copy of the client executable using the new framework and
+//     the deployment target set to the same OS version as BackDeploy 1.0.
+//  6. Run the new executable, verifying with #dsohandle that client copies of
+//     the APIs are used.
+//  7. Re-build the framework in place, this time stripping the definitions of
+//     the back deployed APIs entirely.
+//  8. Re-run the unmodified executable, with the same expectations as in (6).
+//     However, this time we're also verifying that the executable can run even
+//     without the original API symbols present in the linked dylib.
+//
+
+// REQUIRES: executable_test
+// REQUIRES: VENDOR=apple
+
+// ---- (0) Prepare SDK
+// RUN: %empty-directory(%t)
+// RUN: %empty-directory(%t/SDK_ABI)
+// RUN: %empty-directory(%t/SDK_BD)
+
+// ---- (1) Build famework with BackDeploy 2.0 in the past
+// RUN: mkdir -p %t/SDK_ABI/Frameworks/BackDeployHelper.framework/Modules/BackDeployHelper.swiftmodule
+// RUN: %target-build-swift-dylib(%t/SDK_ABI/Frameworks/BackDeployHelper.framework/BackDeployHelper) \
+// RUN:   -emit-module-path %t/SDK_ABI/Frameworks/BackDeployHelper.framework/Modules/BackDeployHelper.swiftmodule/%module-target-triple.swiftmodule \
+// RUN:   -module-name BackDeployHelper -emit-module %S/Inputs/BackDeployHelper.swift \
+// RUN:   -Xfrontend -target -Xfrontend %target-next-stable-abi-triple \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 1.0:macOS 10.14.3, iOS 12.1, tvOS 12.1, watchOS 5.1' \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 2.0:macOS 10.15, iOS 13, tvOS 13, watchOS 6' \
+// RUN:   -Xlinker -install_name -Xlinker @rpath/BackDeployHelper.framework/BackDeployHelper \
+// RUN:   -enable-library-evolution
+
+// ---- (2) Build executable
+// RUN: %target-build-swift -emit-executable %s -g -o %t/test_ABI \
+// RUN:   -Xfrontend -target -Xfrontend %target-pre-stable-abi-triple \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 1.0:macOS 10.14.3, iOS 12.1, tvOS 12.1, watchOS 5.1' \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 2.0:macOS 10.15, iOS 13, tvOS 13, watchOS 6' \
+// RUN:   -F %t/SDK_ABI/Frameworks/ -framework BackDeployHelper \
+// RUN:   %target-rpath(@executable_path/SDK_ABI/Frameworks)
+
+// ---- (3) Run executable
+// RUN: %target-codesign %t/test_ABI
+// RUN: %target-run %t/test_ABI %t/SDK_ABI/Frameworks/BackDeployHelper.framework/BackDeployHelper | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-ABI %s
+
+// ---- (4) Build famework with BackDeploy 2.0 in the future
+// RUN: mkdir -p %t/SDK_BD/Frameworks/BackDeployHelper.framework/Modules/BackDeployHelper.swiftmodule
+// RUN: %target-build-swift-dylib(%t/SDK_BD/Frameworks/BackDeployHelper.framework/BackDeployHelper) \
+// RUN:   -emit-module-path %t/SDK_BD/Frameworks/BackDeployHelper.framework/Modules/BackDeployHelper.swiftmodule/%module-target-triple.swiftmodule \
+// RUN:   -module-name BackDeployHelper -emit-module %S/Inputs/BackDeployHelper.swift \
+// RUN:   -Xfrontend -target -Xfrontend %target-next-stable-abi-triple \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 1.0:macOS 10.14.3, iOS 12.1, tvOS 12.1, watchOS 5.1' \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 2.0:macOS 999.0, iOS 999.0, watchOS 999.0, tvOS 999.0' \
+// RUN:   -Xlinker -install_name -Xlinker @rpath/BackDeployHelper.framework/BackDeployHelper \
+// RUN:   -enable-library-evolution
+
+// ---- (5) Build executable
+// RUN: %target-build-swift -emit-executable %s -g -o %t/test_BD \
+// RUN:   -Xfrontend -target -Xfrontend %target-next-stable-abi-triple \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 1.0:macOS 10.14.3, iOS 12.1, tvOS 12.1, watchOS 5.1' \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 2.0:macOS 999.0, iOS 999.0, watchOS 999.0, tvOS 999.0' \
+// RUN:   -F %t/SDK_BD/Frameworks/ -framework BackDeployHelper \
+// RUN:   %target-rpath(@executable_path/SDK_BD/Frameworks)
+
+// ---- (6) Run executable
+// RUN: %target-codesign %t/test_BD
+// RUN: %target-run %t/test_BD %t/SDK_BD/Frameworks/BackDeployHelper.framework/BackDeployHelper | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-BD %s
+
+// ---- (7) Re-build famework with the back deployed APIs stripped
+// RUN: mkdir -p %t/SDK_BD/Frameworks/BackDeployHelper.framework/Modules/BackDeployHelper.swiftmodule
+// RUN: %target-build-swift-dylib(%t/SDK_BD/Frameworks/BackDeployHelper.framework/BackDeployHelper) \
+// RUN:   -emit-module-path %t/SDK_BD/Frameworks/BackDeployHelper.framework/Modules/BackDeployHelper.swiftmodule/%module-target-triple.swiftmodule \
+// RUN:   -module-name BackDeployHelper -emit-module %S/Inputs/BackDeployHelper.swift \
+// RUN:   -Xfrontend -target -Xfrontend %target-next-stable-abi-triple \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 1.0:macOS 10.14.3, iOS 12.1, tvOS 12.1, watchOS 5.1' \
+// RUN:   -Xfrontend -define-availability \
+// RUN:     -Xfrontend 'BackDeploy 2.0:macOS 999.0, iOS 999.0, watchOS 999.0, tvOS 999.0' \
+// RUN:   -Xlinker -install_name -Xlinker @rpath/BackDeployHelper.framework/BackDeployHelper \
+// RUN:   -enable-library-evolution -DSTRIP_V2_APIS
+
+// ---- (8) Re-run executable
+// RUN: %target-codesign %t/test_BD
+// RUN: %target-run %t/test_BD %t/SDK_BD/Frameworks/BackDeployHelper.framework/BackDeployHelper | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-BD %s
+
+import BackDeployHelper
+
+// CHECK: client: check
+testPrint(handle: #dsohandle, "check")
+// CHECK: library: check
+testPrint(handle: libraryHandle(), "check")
+
+if isV2OrLater() {
+  assert(!v2APIsAreStripped())
+}
+
+// CHECK-ABI: library: trivial
+// CHECK-BD: client: trivial
+trivial()
+
+assert(try! pleaseThrow(false))
+do {
+  _ = try pleaseThrow(true)
+  fatalError("Should have thrown")
+} catch {
+  assert(error as? BadError == BadError.bad)
+}
+
+do {
+  let zero = MutableInt.zero
+  assert(zero.value == 0)
+
+  var int = MutableInt(5)
+
+  // CHECK-ABI: library: 5
+  // CHECK-BD: client: 5
+  int.print()
+
+  assert(int.increment(by: 2) == 7)
+  assert(genericIncrement(&int, by: 3) == 10)
+  assert(int.decrement(by: 1) == 9)
+
+  var incrementable: any Incrementable = int.toIncrementable()
+
+  // CHECK-ABI: library: 10
+  // CHECK-BD: client: 10
+  existentialIncrementByOne(&incrementable)
+
+  let int2 = MutableInt(0x7BB7914B)
+  for (i, expectedByte) in [0x4B, 0x91, 0xB7, 0x7B].enumerated() {
+    assert(int2[byteAt: i] == expectedByte)
+  }
+}
+
+do {
+  let zero = ReferenceInt.zero
+  assert(zero.value == 0)
+
+  var int = ReferenceInt(42)
+
+  // CHECK-ABI: library: 42
+  // CHECK-BD: client: 42
+  int.print()
+
+  do {
+    let copy = int.copy()
+    assert(int !== copy)
+    assert(copy.value == 42)
+  }
+
+  assert(int.increment(by: 2) == 44)
+  assert(genericIncrement(&int, by: 3) == 47)
+  assert(int.decrement(by: 46) == 1)
+
+  var incrementable: any Incrementable = int.toIncrementable()
+
+  // CHECK-ABI: library: 2
+  // CHECK-BD: client: 2
+  existentialIncrementByOne(&incrementable)
+
+  let int2 = MutableInt(0x08AFAB76)
+  for (i, expectedByte) in [0x76, 0xAB, 0xAF, 0x08].enumerated() {
+    assert(int2[byteAt: i] == expectedByte)
+  }
+}