[immediate] Load Foundation early enough for bridging

Foundation needs to be loaded early in the process for Swift's runtime
to properly initialize bridging support; otherwise it may cause issues
like unrecognized selectors. When scripting, load Foundation early in
performFrontend before any swift code runs.

rdar://129528115

Author: benlangmuir

include/swift/AST/DiagnosticsFrontend.def

@@ -115,6 +115,8 @@ ERROR(error_immediate_mode_missing_library,none,
       (unsigned, StringRef))
 ERROR(error_immediate_mode_primary_file,none,
       "immediate mode is incompatible with -primary-file", ())
+WARNING(warning_immediate_mode_cannot_load_foundation,none,
+        "immediate mode failed to load Foundation: %0", (StringRef))
 ERROR(error_missing_frontend_action,none,
       "no frontend action was selected", ())
 ERROR(error_invalid_source_location_str,none,

include/swift/Immediate/Immediate.h

@@ -24,6 +24,7 @@
 
 namespace swift {
   class CompilerInstance;
+  class DiagnosticEngine;
   class IRGenOptions;
   class SILOptions;
   class SILModule;
@@ -44,6 +45,9 @@ namespace swift {
 
   int RunImmediatelyFromAST(CompilerInstance &CI);
 
+  /// On platforms that support ObjC bridging from the Foundation framework,
+  /// ensure that Foundation is loaded early enough. Otherwise does nothing.
+  void loadFoundationIfNeeded(DiagnosticEngine &Diags);
 } // end namespace swift
 
 #endif // SWIFT_IMMEDIATE_IMMEDIATE_H

lib/FrontendTool/FrontendTool.cpp

@@ -1955,6 +1955,13 @@ int swift::performFrontend(ArrayRef<const char *> Args,
     return finishDiagProcessing(1, /*verifierEnabled*/ false);
   }
 
+  // Scripts that use the Foundation framework need it loaded early for bridging
+  // to work correctly on Darwin platforms. On other platforms this is a no-op.
+  if (Invocation.getFrontendOptions().RequestedAction ==
+      FrontendOptions::ActionType::Immediate) {
+    loadFoundationIfNeeded(Instance->getDiags());
+  }
+
   // Don't ask clients to report bugs when running a script in immediate mode.
   // When a script asserts the compiler reports the error with the same
   // stacktrace as a compiler crash. From here we can't tell which is which,

lib/Immediate/Immediate.cpp

@@ -432,3 +432,30 @@ int swift::RunImmediatelyFromAST(CompilerInstance &CI) {
 
   return *Result;
 }
+
+void swift::loadFoundationIfNeeded(DiagnosticEngine &Diags) {
+#if defined(__APPLE__)
+  const char *FoundationPath =
+      "/System/Library/Frameworks/Foundation.framework/Foundation";
+  void *handle = dlopen(FoundationPath, RTLD_NOLOAD);
+  if (handle) {
+    // Foundation is already loaded. Use dlclose to release the ref-count that
+    // was incremented by dlopen and return.
+    dlclose(handle);
+    return;
+  } else {
+    // Foundation is not yet loaded. Load it now and leak the handle.
+    // FIXME: it is fragile to load here, as there is no guarantee the swift
+    // runtime has not initialized already. As the compiler adds more swift code
+    // we may need to move this or find another solution.
+    handle = dlopen(FoundationPath, RTLD_LAZY | RTLD_GLOBAL);
+    if (!handle)
+      Diags.diagnose(SourceLoc(),
+                     diag::warning_immediate_mode_cannot_load_foundation,
+                     dlerror());
+  }
+
+#else
+  // Nothing to do.
+#endif
+}

test/Interpreter/foundation-bridge-error.swift

@@ -0,0 +1,25 @@
+// Check that we can access localizedDescription, which crashes in the runtime
+// if Foundation is loaded after the runtime is already initialized on Darwin.
+
+// REQUIRES: executable_test
+// REQUIRES: objc_interop
+// REQUIRES: OS=macosx
+
+// FIXME: There's a separate bridging error with the just-built stdlib on CI
+// nodes.
+// REQUIRES: use_os_stdlib
+
+// RUN: %target-jit-run %s
+// RUN: DYLD_INSERT_LIBRARIES=/System/Library/Frameworks/Foundation.framework/Foundation %target-jit-run %s
+
+import Foundation
+
+print("Insert Libraries: \(ProcessInfo.processInfo.environment["DYLD_INSERT_LIBRARIES"] ?? "<nil>")")
+
+enum SomeError: LocalizedError {
+ case fail
+}
+
+let err = SomeError.fail
+let path = (#file as NSString).lastPathComponent
+let desc = err.localizedDescription