[Runtime] Look up Error bridging symbols indirectly through special symbols that won't be stripped in static builds.

stdlib/public/SDK/Foundation/CMakeLists.txt

@@ -26,6 +26,7 @@ add_swift_library(swiftFoundation ${SWIFT_SDK_OVERLAY_LIBRARY_BUILD_TYPES} IS_SD
   NSCoder.swift
   NSDate.swift
   NSDictionary.swift
+  NSError.c
   NSError.swift
   NSExpression.swift
   NSFastEnumeration.swift

stdlib/public/SDK/Foundation/NSError.c

@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2018 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "swift/Runtime/Config.h"
+
+#if SWIFT_OBJC_INTEROP
+#include "swift/Demangling/ManglingMacros.h"
+
+// Declare dynamic lookup points for ErrorObject.mm. It uses dlsym to
+// find these symbols to locate NS/CFError Error conformance tables and
+// related items. The .desc asm directive ensures that they are
+// preserved even when statically linked into an executable and
+// stripped, so that the dlsym lookup still works.
+#define ERROROBJECT_DYNAMIC_LOOKUP_POINT(symbol) \
+  extern void *MANGLE_SYM(symbol); \
+  void **MANGLING_CONCAT2(ErrorObjectLookup_, MANGLE_SYM(symbol)) = &MANGLE_SYM(symbol); \
+  asm(".desc _ErrorObjectLookup_" MANGLE_AS_STRING(MANGLE_SYM(symbol)) ", 0x10");
+
+ERROROBJECT_DYNAMIC_LOOKUP_POINT(So10CFErrorRefas5Error10FoundationWa)
+ERROROBJECT_DYNAMIC_LOOKUP_POINT(So8NSObjectCs8Hashable10ObjectiveCWa)
+ERROROBJECT_DYNAMIC_LOOKUP_POINT(10Foundation24_getErrorDefaultUserInfoyyXlSgxs0C0RzlF)
+ERROROBJECT_DYNAMIC_LOOKUP_POINT(10Foundation21_bridgeNSErrorToError_3outSbSo0C0C_SpyxGtAA021_ObjectiveCBridgeableE0RzlF)
+ERROROBJECT_DYNAMIC_LOOKUP_POINT(10Foundation26_ObjectiveCBridgeableErrorMp)
+
+#endif

stdlib/public/runtime/ErrorObject.mm

@@ -220,6 +220,21 @@ static Class getSwiftNativeNSErrorClass() {
   object_dispose((id)error);
 }
 
+/// Look up a symbol that points to something else. Treats the symbol as
+/// a void** and dereferences it if it's non-NULL. Returns NULL if the
+/// symbol can't be found or if the value is NULL.
+static void *dynamicLookupSymbol(const char *name) {
+  void **ptr = reinterpret_cast<void **>(dlsym(RTLD_DEFAULT, name));
+  if (!ptr) return nullptr;
+  return *ptr;
+}
+
+/// Look up an indirect pointer to a mangled Swift symbol, automatically
+/// prepending the ErrorObjectLookup_ prefix. Used to find the various
+/// Foundation overlay symbols for Error bridging.
+#define DYNAMIC_LOOKUP_SYMBOL(symbol) \
+  dynamicLookupSymbol("ErrorObjectLookup_" MANGLE_AS_STRING(MANGLE_SYM(symbol)))
+
 static const WitnessTable *getNSErrorConformanceToError() {
   // CFError and NSError are toll-free-bridged, so we can use either type's
   // witness table interchangeably. CFError's is potentially slightly more
@@ -228,8 +243,7 @@ static Class getSwiftNativeNSErrorClass() {
   // to assume that that's been linked in if a user is using NSError in their
   // Swift source.
 
-  auto TheWitnessTable = SWIFT_LAZY_CONSTANT(dlsym(RTLD_DEFAULT,
-      MANGLE_AS_STRING(MANGLE_SYM(So10CFErrorRefas5Error10FoundationWa))));
+  auto TheWitnessTable = SWIFT_LAZY_CONSTANT(DYNAMIC_LOOKUP_SYMBOL(So10CFErrorRefas5Error10FoundationWa));
   assert(TheWitnessTable &&
          "Foundation overlay not loaded, or 'CFError : Error' conformance "
          "not available");
@@ -238,8 +252,7 @@ static Class getSwiftNativeNSErrorClass() {
 }
 
 static const HashableWitnessTable *getNSErrorConformanceToHashable() {
-  auto TheWitnessTable = SWIFT_LAZY_CONSTANT(dlsym(RTLD_DEFAULT,
-           MANGLE_AS_STRING(MANGLE_SYM(So8NSObjectCs8Hashable10ObjectiveCWa))));
+  auto TheWitnessTable = SWIFT_LAZY_CONSTANT(DYNAMIC_LOOKUP_SYMBOL(So8NSObjectCs8Hashable10ObjectiveCWa));
   assert(TheWitnessTable &&
          "ObjectiveC overlay not loaded, or 'NSObject : Hashable' conformance "
          "not available");
@@ -379,8 +392,7 @@ typedef SWIFT_CC(swift)
   // public func Foundation._getErrorDefaultUserInfo<T: Error>(_ error: T)
   //   -> AnyObject?
   auto foundationGetDefaultUserInfo = SWIFT_LAZY_CONSTANT(
-    reinterpret_cast<GetDefaultFn*> (dlsym(RTLD_DEFAULT,
-    MANGLE_AS_STRING(MANGLE_SYM(10Foundation24_getErrorDefaultUserInfoyyXlSgxs0C0RzlF)))));
+    reinterpret_cast<GetDefaultFn*> (DYNAMIC_LOOKUP_SYMBOL(10Foundation24_getErrorDefaultUserInfoyyXlSgxs0C0RzlF)));
   if (!foundationGetDefaultUserInfo) {
     SWIFT_CC_PLUSONE_GUARD(T->vw_destroy(error));
     return nullptr;
@@ -520,12 +532,10 @@ typedef SWIFT_CC(swift)
     bool BridgeFn(NSError *, OpaqueValue*, const Metadata *,
                   const WitnessTable *);
   auto bridgeNSErrorToError = SWIFT_LAZY_CONSTANT(
-    reinterpret_cast<BridgeFn*>(dlsym(RTLD_DEFAULT,
-    MANGLE_AS_STRING(MANGLE_SYM(10Foundation21_bridgeNSErrorToError_3outSbSo0C0C_SpyxGtAA021_ObjectiveCBridgeableE0RzlF)))));
+    reinterpret_cast<BridgeFn*>(DYNAMIC_LOOKUP_SYMBOL(10Foundation21_bridgeNSErrorToError_3outSbSo0C0C_SpyxGtAA021_ObjectiveCBridgeableE0RzlF)));
   // protocol _ObjectiveCBridgeableError
   auto TheObjectiveCBridgeableError = SWIFT_LAZY_CONSTANT(
-    reinterpret_cast<const ProtocolDescriptor *>(dlsym(RTLD_DEFAULT,
-    MANGLE_AS_STRING(MANGLE_SYM(10Foundation26_ObjectiveCBridgeableErrorMp)))));
+    reinterpret_cast<const ProtocolDescriptor *>(DYNAMIC_LOOKUP_SYMBOL(10Foundation26_ObjectiveCBridgeableErrorMp)));
 
   // If the Foundation overlay isn't loaded, then arbitrary NSErrors can't be
   // bridged.

test/stdlib/ErrorBridgedStatic.swift

@@ -14,6 +14,10 @@ class Bar: Foo {
   override func foo(_ x: Int32) throws {
     try super.foo(5)
   }
+
+  override func foothrows(_ x: Int32) throws {
+    try super.foothrows(5)
+  }
 }
 
 var ErrorBridgingStaticTests = TestSuite("ErrorBridging with static libs")
@@ -24,4 +28,14 @@ ErrorBridgingStaticTests.test("round-trip Swift override of ObjC method") {
   } catch { }
 }
 
+ErrorBridgingStaticTests.test("round-trip Swift override of throwing ObjC method") {
+  do {
+    try (Bar() as Foo).foothrows(5)
+  } catch {
+    print(error)
+    expectEqual(error._domain, "abcd")
+    expectEqual(error._code, 1234)
+  }
+}
+
 runAllTests()

test/stdlib/Inputs/ErrorBridgedStaticImpl.h

@@ -3,5 +3,6 @@
 @interface Foo: NSObject
 
 - (BOOL)foo:(int)x error:(NSError**)error;
+- (BOOL)foothrows:(int)x error:(NSError**)error;
 
 @end

test/stdlib/Inputs/ErrorBridgedStaticImpl.m

@@ -7,5 +7,10 @@ - (BOOL)foo:(int)x error:(NSError**)error {
   return NO;
 }
 
+- (BOOL)foothrows:(int)x error:(NSError**)error {
+  *error = [NSError errorWithDomain: @"abcd" code: 1234 userInfo: nil];
+  return NO;
+}
+
 @end