[5.0] DynamicReplacement: Don't fail when a library is closed and reloaded

stdlib/public/runtime/MetadataLookup.cpp

@@ -1677,11 +1677,15 @@ void DynamicReplacementDescriptor::enableReplacement() const {
       replacedFunctionKey->root.get());
 
   // Make sure this entry is not already enabled.
+  // This does not work until we make sure that when a dynamic library is
+  // unloaded all descriptors are removed.
+#if 0
   for (auto *curr = chainRoot; curr != nullptr; curr = curr->next) {
     if (curr == chainEntry.get()) {
       swift::swift_abortDynamicReplacementEnabling();
     }
   }
+#endif
 
   // Unlink the previous entry if we are not chaining.
   if (!shouldChain() && chainRoot->next) {

test/Interpreter/Inputs/dynamic_replacement_dlclose.swift

@@ -0,0 +1,9 @@
+struct A {
+  dynamic var value : Int {
+    return 1
+  }
+}
+
+public func test() -> Int{
+  return A().value
+}

test/Interpreter/Inputs/dynamic_replacement_dlclose2.swift

@@ -0,0 +1,8 @@
+@_private(sourceFile: "dynamic_replacement_dlclose.swift") import Module1
+
+extension A {
+  @_dynamicReplacement(for: value)
+  var repl: Int {
+    return 2
+  }
+}

test/Interpreter/dynamic_replacement_dlclose.swift

@@ -0,0 +1,70 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift-dylib(%t/libModule1.%target-dylib-extension) -DMODULE -module-name Module1 -emit-module -emit-module-path %t/Module1.swiftmodule -swift-version 5 %S/Inputs/dynamic_replacement_dlclose.swift -Xfrontend -enable-private-imports
+// RUN: %target-build-swift-dylib(%t/libModule2.%target-dylib-extension) -I%t -L%t -lModule1 -Xlinker -rpath -Xlinker %t -DMODULE2 -module-name Module2 -emit-module -emit-module-path %t/Module2.swiftmodule -swift-version 5 %S/Inputs/dynamic_replacement_dlclose2.swift
+// RUN: %target-build-swift -I%t -L%t -lModule1 -DMAIN -o %t/main -Xlinker -rpath -Xlinker %t %s -swift-version 5
+// RUN: %target-codesign %t/main %t/libModule1.%target-dylib-extension %t/libModule2.%target-dylib-extension
+// RUN: %target-run %t/main %t/libModule1.%target-dylib-extension %t/libModule2.%target-dylib-extension
+
+
+import Module1
+
+import StdlibUnittest
+
+#if os(Linux)
+  import Glibc
+#elseif os(Windows)
+  import MSVCRT
+  import WinSDK
+#else
+  import Darwin
+#endif
+
+var DynamicallyReplaceable = TestSuite("DynamicallyReplaceable")
+
+
+
+private func target_library_name(_ name: String) -> String {
+#if os(iOS) || os(macOS) || os(tvOS) || os(watchOS)
+  return "lib\(name).dylib"
+#elseif os(Windows)
+  return "\(name).dll"
+#else
+  return "lib\(name).so"
+#endif
+}
+
+
+DynamicallyReplaceable.test("DynamicallyReplaceable") {
+  var executablePath = CommandLine.arguments[0]
+  executablePath.removeLast(4)
+  expectEqual(1, test())
+  // Now, test with the module containing the replacements.
+
+#if os(Linux)
+	let h = dlopen(target_library_name("Module2"), RTLD_NOW)
+#elseif os(Windows)
+  let h = LoadLibraryA(target_library_name("Module2"))
+#else
+	let h = dlopen(executablePath+target_library_name("Module2"), RTLD_NOW)
+#endif
+
+  expectEqual(2, test())
+
+#if os(Linux)
+  dlclose(h!)
+#elseif os(Windows)
+#else
+  dlclose(h)
+#endif
+
+#if os(Linux)
+  _ = dlopen(target_library_name("Module2"), RTLD_NOW)
+#elseif os(Windows)
+#else
+	_ = dlopen(executablePath+target_library_name("Module2"), RTLD_NOW)
+#endif
+  expectEqual(2, test())
+
+}
+
+runAllTests()