Ignore -no_exported_symbols when the debug dylib is used (rdar://152244838) (#554)

The stub executor needs to trampoline to the entry point in the debug dylib. But linking with `-no_exported_symbols` strips it and launching the app fails to find the symbol.

Handles both the `LD_EXPORT_SYMBOLS` build setting and manual flags added to `OTHER_LDFLAGS`.

Author: jonathanpenn

Sources/SWBCore/Settings/BuiltinMacros.swift

@@ -805,6 +805,7 @@ public final class BuiltinMacros {
     public static let LD_DEPENDENCY_INFO_FILE = BuiltinMacros.declarePathMacro("LD_DEPENDENCY_INFO_FILE")
     public static let LD_DYLIB_INSTALL_NAME = BuiltinMacros.declareStringMacro("LD_DYLIB_INSTALL_NAME")
     public static let LD_ENTRY_POINT = BuiltinMacros.declareStringMacro("LD_ENTRY_POINT")
+    public static let LD_EXPORT_SYMBOLS = BuiltinMacros.declareBooleanMacro("LD_EXPORT_SYMBOLS")
     public static let LD_EXPORT_GLOBAL_SYMBOLS = BuiltinMacros.declareBooleanMacro("LD_EXPORT_GLOBAL_SYMBOLS")
     public static let LD_LTO_OBJECT_FILE = BuiltinMacros.declarePathMacro("LD_LTO_OBJECT_FILE")
     public static let LD_NO_PIE = BuiltinMacros.declareBooleanMacro("LD_NO_PIE")
@@ -1871,6 +1872,7 @@ public final class BuiltinMacros {
         LD_ENTRY_POINT,
         LD_ENTITLEMENTS_SECTION,
         LD_ENTITLEMENTS_SECTION_DER,
+        LD_EXPORT_SYMBOLS,
         LD_EXPORT_GLOBAL_SYMBOLS,
         LD_LTO_OBJECT_FILE,
         LD_NO_PIE,

Sources/SWBCore/SpecImplementations/Tools/LinkerTools.swift

@@ -314,6 +314,8 @@ public final class LdLinkerSpec : GenericLinkerSpec, SpecIdentifierType, @unchec
                 delegate.emit(Diagnostic(behavior: dyldEnvDiagnosticBehavior, location: .buildSetting(BuiltinMacros.OTHER_LDFLAGS), data: DiagnosticData("The \(BuiltinMacros.OTHER_LDFLAGS.name) build setting is not allowed to contain \(arg), use the dedicated LD_ENVIRONMENT build setting instead.")))
             case "-client_name":
                 delegate.emit(Diagnostic(behavior: dyldEnvDiagnosticBehavior, location: .buildSetting(BuiltinMacros.OTHER_LDFLAGS), data: DiagnosticData("The \(BuiltinMacros.OTHER_LDFLAGS.name) build setting is not allowed to contain \(arg), use the dedicated LD_CLIENT_NAME build setting instead.")))
+            case "-no_exported_symbols":
+                delegate.emit(Diagnostic(behavior: dyldEnvDiagnosticBehavior, location: .buildSetting(BuiltinMacros.OTHER_LDFLAGS), data: DiagnosticData("The \(BuiltinMacros.OTHER_LDFLAGS.name) build setting is not allowed to contain \(arg), use the dedicated LD_EXPORT_SYMBOLS build setting instead.")))
             default:
                 break
             }
@@ -504,6 +506,15 @@ public final class LdLinkerSpec : GenericLinkerSpec, SpecIdentifierType, @unchec
                     return nil
                 }
                 return cbc.scope.namespace.parseLiteralString(name)
+            case BuiltinMacros.DEAD_CODE_STRIPPING where isPreviewDylib:
+                // We need to keep otherwise unused stub executor library symbols present so
+                // PreviewsInjection can call them when doing the XOJIT handshake.
+                return cbc.scope.namespace.parseLiteralString("NO")
+            case BuiltinMacros.LD_EXPORT_SYMBOLS where isPreviewDylib,
+                BuiltinMacros.LD_EXPORT_GLOBAL_SYMBOLS where isPreviewDylib:
+                // We need to keep otherwise unused stub executor library symbols present so
+                // PreviewsInjection can call them when doing the XOJIT handshake.
+                return cbc.scope.namespace.parseLiteralString("YES")
             case BuiltinMacros.OTHER_LDFLAGS where isPreviewDylib:
                 let ldFlagsToEvaluate: [String]
                 if dyldEnvDiagnosticBehavior == .warning {
@@ -774,7 +785,7 @@ public final class LdLinkerSpec : GenericLinkerSpec, SpecIdentifierType, @unchec
             switch macro {
             case BuiltinMacros.LD_ENTRY_POINT where cbc.scope.previewStyle == .xojit:
                 return cbc.scope.namespace.parseLiteralString("___debug_blank_executor_main")
-            case BuiltinMacros.LD_EXPORT_GLOBAL_SYMBOLS:
+            case BuiltinMacros.LD_EXPORT_SYMBOLS, BuiltinMacros.LD_EXPORT_GLOBAL_SYMBOLS:
                 // We need to keep otherwise unused stub executor library symbols present so
                 // PreviewsInjection can call them when doing the XOJIT handshake.
                 return cbc.scope.namespace.parseLiteralString("YES")
@@ -1821,6 +1832,23 @@ fileprivate func filterLinkerFlagsWhenUnderPreviewsDylib(_ flags: [String]) -> [
             }
             continue
         }
+        else if flag == "-Wl,-no_exported_symbols" {
+            continue
+        }
+        else if flag == "-no_exported_symbols" && newFlags.last == "-Xlinker" {
+            // Filter out `-no_exported_symbols` when using the previews dylib, since this
+            // strips important symbols that are needed for the stub executor trampoline..
+            // Transition from `OTHER_LD_FLAGS` to the dedicated `LD_EXPORT_SYMBOLS` (by
+            // defining both at once) in order to remain compatible with Xcode versions both
+            // before and after this change.
+            newFlags.removeLast()
+            while let next = it.next() {
+                if next != "-Xlinker" {
+                    break
+                }
+            }
+            continue
+        }
         newFlags.append(flag)
     }
     return newFlags

Tests/SWBBuildSystemTests/PreviewsBuildOperationTests.swift

@@ -308,7 +308,7 @@ fileprivate struct PreviewsBuildOperationTests: CoreBasedTests {
                                 linkerCommandLine.remove(at: idx)
                             }
                         }
-                        XCTAssertEqualSequences(linkerCommandLine, ["\(core.developerPath.path.str)/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang", "-Xlinker", "-reproducible", "-target", "\(results.runDestinationTargetArchitecture)-apple-ios\(core.loadSDK(.iOSSimulator).defaultDeploymentTarget)-simulator", "-dynamiclib", "-isysroot", core.loadSDK(.iOSSimulator).path.str, "-Os", "-Xlinker", "-warn_unused_dylibs", "-L\(srcRoot.str)/build/EagerLinkingTBDs/Debug-iphonesimulator", "-L\(srcRoot.str)/build/Debug-iphonesimulator", "-F\(srcRoot.str)/build/EagerLinkingTBDs/Debug-iphonesimulator", "-F\(srcRoot.str)/build/Debug-iphonesimulator", "-filelist", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget.LinkFileList", "-install_name", "@rpath/AppTarget.debug.dylib", "-dead_strip", "-Xlinker", "-object_path_lto", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget_lto.o", "-Xlinker", "-objc_abi_version", "-Xlinker", "2", "-Xlinker", "-dependency_info", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget_dependency_info.dat", "-L\(core.developerPath.path.str)/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/iphonesimulator", "-L/usr/lib/swift", "-Xlinker", "-add_ast_path", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget.swiftmodule", "-Xlinker", "-alias", "-Xlinker", "_main", "-Xlinker", "___debug_main_executable_dylib_entry_point", "-Xlinker", "-no_adhoc_codesign", "-o", "\(srcRoot.str)/build/Debug-iphonesimulator/AppTarget.app/AppTarget.debug.dylib"])
+                        XCTAssertEqualSequences(linkerCommandLine, ["\(core.developerPath.path.str)/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang", "-Xlinker", "-reproducible", "-target", "\(results.runDestinationTargetArchitecture)-apple-ios\(core.loadSDK(.iOSSimulator).defaultDeploymentTarget)-simulator", "-dynamiclib", "-isysroot", core.loadSDK(.iOSSimulator).path.str, "-Os", "-Xlinker", "-warn_unused_dylibs", "-L\(srcRoot.str)/build/EagerLinkingTBDs/Debug-iphonesimulator", "-L\(srcRoot.str)/build/Debug-iphonesimulator", "-F\(srcRoot.str)/build/EagerLinkingTBDs/Debug-iphonesimulator", "-F\(srcRoot.str)/build/Debug-iphonesimulator", "-filelist", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget.LinkFileList", "-install_name", "@rpath/AppTarget.debug.dylib", "-Xlinker", "-object_path_lto", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget_lto.o", "-rdynamic", "-Xlinker", "-objc_abi_version", "-Xlinker", "2", "-Xlinker", "-dependency_info", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget_dependency_info.dat", "-L\(core.developerPath.path.str)/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/iphonesimulator", "-L/usr/lib/swift", "-Xlinker", "-add_ast_path", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget.swiftmodule", "-Xlinker", "-alias", "-Xlinker", "_main", "-Xlinker", "___debug_main_executable_dylib_entry_point", "-Xlinker", "-no_adhoc_codesign", "-o", "\(srcRoot.str)/build/Debug-iphonesimulator/AppTarget.app/AppTarget.debug.dylib"])
                     }
                 }
 
@@ -615,7 +615,7 @@ fileprivate struct PreviewsBuildOperationTests: CoreBasedTests {
                                 linkerCommandLine.remove(at: idx)
                             }
                         }
-                        XCTAssertEqualSequences(linkerCommandLine, ["\(core.developerPath.path.str)/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang", "-Xlinker", "-reproducible", "-target", "\(results.runDestinationTargetArchitecture)-apple-ios\(core.loadSDK(.iOSSimulator).defaultDeploymentTarget)-simulator", "-dynamiclib", "-isysroot", core.loadSDK(.iOSSimulator).path.str, "-Os", "-L\(srcRoot.str)/build/EagerLinkingTBDs/Debug-iphonesimulator", "-L\(srcRoot.str)/build/Debug-iphonesimulator", "-F\(srcRoot.str)/build/EagerLinkingTBDs/Debug-iphonesimulator", "-F\(srcRoot.str)/build/Debug-iphonesimulator", "-filelist", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget.LinkFileList", "-install_name", "@rpath/AppTarget.debug.dylib", "-dead_strip", "-Xlinker", "-object_path_lto", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget_lto.o", "-Xlinker", "-objc_abi_version", "-Xlinker", "2", "-Xlinker", "-dependency_info", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget_dependency_info.dat", "-fobjc-link-runtime", "-L\(core.developerPath.path.str)/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/iphonesimulator", "-L/usr/lib/swift", "-Xlinker", "-add_ast_path", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget.swiftmodule", "-Xlinker", "-alias", "-Xlinker", "_main", "-Xlinker", "___debug_main_executable_dylib_entry_point", "-Xlinker", "-no_adhoc_codesign", "-o", "\(srcRoot.str)/build/Debug-iphonesimulator/AppTarget.app/AppTarget.debug.dylib"])
+                        XCTAssertEqualSequences(linkerCommandLine, ["\(core.developerPath.path.str)/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang", "-Xlinker", "-reproducible", "-target", "\(results.runDestinationTargetArchitecture)-apple-ios\(core.loadSDK(.iOSSimulator).defaultDeploymentTarget)-simulator", "-dynamiclib", "-isysroot", core.loadSDK(.iOSSimulator).path.str, "-Os", "-L\(srcRoot.str)/build/EagerLinkingTBDs/Debug-iphonesimulator", "-L\(srcRoot.str)/build/Debug-iphonesimulator", "-F\(srcRoot.str)/build/EagerLinkingTBDs/Debug-iphonesimulator", "-F\(srcRoot.str)/build/Debug-iphonesimulator", "-filelist", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget.LinkFileList", "-install_name", "@rpath/AppTarget.debug.dylib", "-Xlinker", "-object_path_lto", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget_lto.o", "-rdynamic", "-Xlinker", "-objc_abi_version", "-Xlinker", "2", "-Xlinker", "-dependency_info", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget_dependency_info.dat", "-fobjc-link-runtime", "-L\(core.developerPath.path.str)/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/iphonesimulator", "-L/usr/lib/swift", "-Xlinker", "-add_ast_path", "-Xlinker", "\(srcRoot.str)/build/ProjectName.build/Debug-iphonesimulator/AppTarget.build/Objects-normal/\(results.runDestinationTargetArchitecture)/AppTarget.swiftmodule", "-Xlinker", "-alias", "-Xlinker", "_main", "-Xlinker", "___debug_main_executable_dylib_entry_point", "-Xlinker", "-no_adhoc_codesign", "-o", "\(srcRoot.str)/build/Debug-iphonesimulator/AppTarget.app/AppTarget.debug.dylib"])
                     }
                 }
             }

Tests/SWBTaskConstructionTests/PreviewsTaskConstructionTests.swift

@@ -932,7 +932,7 @@ fileprivate struct PreviewsTaskConstructionTests: CoreBasedTests {
 
     /// Test that the `__info_plist` section ends up in the stub executor instead of the preview dylib when `CREATE_INFOPLIST_SECTION_IN_BINARY` is enabled.
     @Test(.requireSDKs(.iOS))
-    func xOJITEmbeddedInfoPlist() async throws {
+    func XOJITEmbeddedInfoPlist() async throws {
         try await withTemporaryDirectory { tmpDirPath in
             let srcRoot = tmpDirPath.join("srcroot")
 
@@ -1019,9 +1019,9 @@ fileprivate struct PreviewsTaskConstructionTests: CoreBasedTests {
         }
     }
 
-    /// Test that any `-dyld_env` arguments end up in the stub executor instead of the preview dylib when is enabled.
+    /// Test that any `OTHER_LDFLAGS` arguments end up in the stub executor instead of the debug dylib when is enabled.
     @Test(.requireSDKs(.iOS))
-    func xOJITDyldEnv() async throws {
+    func XOJITOtherLDFlags() async throws {
         try await withTemporaryDirectory { tmpDirPath in
             let srcRoot = tmpDirPath.join("srcroot")
 
@@ -1037,7 +1037,11 @@ fileprivate struct PreviewsTaskConstructionTests: CoreBasedTests {
                 buildConfigurations: [
                     TestBuildConfiguration("Debug", buildSettings: [
                         "LD_ENVIRONMENT": "DYLD_X_PATH=/foo",
-                        "OTHER_LDFLAGS": "-Wl,-dyld_env,NOT=allowed_here -Xlinker -dyld_env -Xlinker NOR=this",
+                        "OTHER_LDFLAGS": """
+                            -Wl,-dyld_env,NOT=allowed_here -Xlinker -dyld_env -Xlinker NOR=this \
+                            -Wl,-no_exported_symbols -Xlinker -no_exported_symbols
+                            """,
+                        "LD_EXPORT_SYMBOLS": "NO",
                         "GENERATE_INFOPLIST_FILE": "YES",
                         "PRODUCT_NAME": "$(TARGET_NAME)",
                         "PRODUCT_BUNDLE_IDENTIFIER": "com.test.ProjectName",
@@ -1100,20 +1104,26 @@ fileprivate struct PreviewsTaskConstructionTests: CoreBasedTests {
                     // from OTHER_LDFLAGS, which is overridden to a custom set of flags _without_ $(inherited), so the stub executor doesn't get them
                     task.checkCommandLineDoesNotContain("-Wl,-dyld_env,NOT=allowed_here")
                     task.checkCommandLineDoesNotContain("NOR=this")
+                    task.checkCommandLineDoesNotContain("-Wl,-no_exported_symbols")
+                    task.checkCommandLineDoesNotContain("-no_exported_symbols")
                 }
 
                 results.checkTask(.matchRule(["Ld", "\(srcRoot.str)/build/Debug-iphonesimulator/Tool.debug.dylib", "normal"])) { task in
-                    // from LD_ENVIRONMENT, which is conditional on MACH_O_TYPE=mh_execute, so the previews dylib (which overrides MACH_O_TYPE=mh_dylib) doesn't get it
+                    // from LD_ENVIRONMENT, which is conditional on MACH_O_TYPE=mh_execute, so the debug dylib (which overrides MACH_O_TYPE=mh_dylib) doesn't get it
                     task.checkCommandLineDoesNotContain("-dyld_env")
                     task.checkCommandLineDoesNotContain("DYLD_X_PATH=/foo")
 
-                    // from OTHER_LDFLAGS, which is passed through unchanged to the previews dylib
+                    // from OTHER_LDFLAGS, which is passed through unchanged to the debug dylib
                     task.checkCommandLineDoesNotContain("-Wl,-dyld_env,NOT=allowed_here")
                     task.checkCommandLineDoesNotContain("NOR=this")
+                    task.checkCommandLineDoesNotContain("-Wl,-no_exported_symbols")
+                    task.checkCommandLineDoesNotContain("-no_exported_symbols")
                 }
 
                 results.checkWarning(.equal("The OTHER_LDFLAGS build setting is not allowed to contain -dyld_env, use the dedicated LD_ENVIRONMENT build setting instead. (in target 'Tool' from project 'ProjectName')"))
                 results.checkWarning(.equal("The OTHER_LDFLAGS build setting is not allowed to contain -dyld_env, use the dedicated LD_ENVIRONMENT build setting instead. (in target 'Tool' from project 'ProjectName')"))
+                results.checkWarning(.equal("The OTHER_LDFLAGS build setting is not allowed to contain -no_exported_symbols, use the dedicated LD_EXPORT_SYMBOLS build setting instead. (in target 'Tool' from project 'ProjectName')"))
+                results.checkWarning(.equal("The OTHER_LDFLAGS build setting is not allowed to contain -no_exported_symbols, use the dedicated LD_EXPORT_SYMBOLS build setting instead. (in target 'Tool' from project 'ProjectName')"))
 
                 results.checkNoTask()
                 results.checkNoDiagnostics()
@@ -1123,7 +1133,7 @@ fileprivate struct PreviewsTaskConstructionTests: CoreBasedTests {
     }
 
     @Test(.requireSDKs(.iOS))
-    func xOJITPropagatingRpaths() async throws {
+    func XOJITPropagatingRpaths() async throws {
         try await withTemporaryDirectory { tmpDirPath in
             let srcRoot = tmpDirPath.join("srcroot")
 

Tests/SwiftBuildTests/GeneratePreviewInfoTests.swift

@@ -229,11 +229,11 @@ fileprivate struct GeneratePreviewInfoTests: CoreBasedTests {
                                 "\(tmpDir.str)/Test/build/Test.build/Debug-iphoneos/App.build/Objects-normal/\(activeRunDestination.targetArchitecture)/App.LinkFileList",
                                 "-install_name",
                                 "@rpath/App.debug.dylib",
-                                "-dead_strip",
                                 "-Xlinker",
                                 "-object_path_lto",
                                 "-Xlinker",
                                 "\(tmpDir.str)/Test/build/Test.build/Debug-iphoneos/App.build/Objects-normal/\(activeRunDestination.targetArchitecture)/App_lto.o",
+                                "-rdynamic",
                                 "-Xlinker",
                                 "-dependency_info",
                                 "-Xlinker",