[6.0] Support macros when cross-compiling

CHANGELOG.md

@@ -27,13 +27,18 @@ Swift 6.0
 
   `// swift-tools-version:` can now be specified on subsequent lines of `Package.swift`, for example when first few lines are required to contain a licensing comment header.
 
+* [#7118]
+
+  Macros cross-compiled by SwiftPM with Swift SDKs are now correctly built, loaded, and evaluated for the host triple.
+
 Swift 5.10
 -----------
+
 * [#7010]
 
   On macOS, `swift build` and `swift run` now produce binaries that allow backtraces in debug builds. Pass `SWIFT_BACKTRACE=enable=yes` environment variable to enable backtraces on such binaries when running them.
 
-* [7101]
+* [#7101]
 
    Binary artifacts are now cached along side repository checkouts so they do not need to be re-downloaded across projects.
 

Sources/Basics/Collections/IdentifiableSet.swift

@@ -47,13 +47,22 @@ public struct IdentifiableSet<Element: Identifiable>: Collection {
     }
 
     public subscript(id: Element.ID) -> Element? {
-        self.storage[id]
+        get {
+            self.storage[id]
+        }
+        set {
+            self.storage[id] = newValue
+        }
     }
 
     public func index(after i: Index) -> Index {
         Index(storageIndex: self.storage.elements.index(after: i.storageIndex))
     }
 
+    public mutating func insert(_ element: Element) {
+        self.storage[element.id] = element
+    }
+
     public func union(_ otherSequence: some Sequence<Element>) -> Self {
         var result = self
         for element in otherSequence {

Sources/Basics/Errors.swift

@@ -21,8 +21,7 @@ public struct InternalError: Error {
     private let description: String
     public init(_ description: String) {
         assertionFailure(description)
-        self
-            .description =
+        self.description =
             "Internal error. Please file a bug at https://github.com/apple/swift-package-manager/issues with this info. \(description)"
     }
 }

Sources/Build/BuildDescription/ClangTargetBuildDescription.swift

@@ -53,7 +53,7 @@ public final class ClangTargetBuildDescription {
 
     /// Path to the bundle generated for this module (if any).
     var bundlePath: AbsolutePath? {
-        guard !resources.isEmpty else {
+        guard !self.resources.isEmpty else {
             return .none
         }
 
@@ -133,7 +133,7 @@ public final class ClangTargetBuildDescription {
         self.target = target
         self.toolsVersion = toolsVersion
         self.buildParameters = buildParameters
-        self.tempsPath = buildParameters.buildPath.appending(component: target.c99name + ".build")
+        self.tempsPath = target.tempsPath(buildParameters)
         self.derivedSources = Sources(paths: [], root: tempsPath.appending("DerivedSources"))
 
         // We did not use to apply package plugins to C-family targets in prior tools-versions, this preserves the behavior.
@@ -225,7 +225,7 @@ public final class ClangTargetBuildDescription {
         if self.buildParameters.triple.isDarwin() {
             args += ["-fobjc-arc"]
         }
-        args += try buildParameters.targetTripleArgs(for: target)
+        args += try self.buildParameters.tripleArgs(for: target)
 
         args += optimizationArguments
         args += activeCompilationConditions

Sources/Build/BuildDescription/ProductBuildDescription.swift

@@ -322,7 +322,7 @@ public final class ProductBuildDescription: SPMBuildCore.ProductBuildDescription
         // setting is the package-level right now. We might need to figure out a better
         // answer for libraries if/when we support specifying deployment target at the
         // target-level.
-        args += try self.buildParameters.targetTripleArgs(for: self.product.targets[self.product.targets.startIndex])
+        args += try self.buildParameters.tripleArgs(for: self.product.targets[self.product.targets.startIndex])
 
         // Add arguments from declared build settings.
         args += self.buildSettingsFlags
@@ -357,7 +357,7 @@ public final class ProductBuildDescription: SPMBuildCore.ProductBuildDescription
         // Library search path for the toolchain's copy of SwiftSyntax.
         #if BUILD_MACROS_AS_DYLIBS
         if product.type == .macro {
-            args += try ["-L", buildParameters.toolchain.hostLibDir.pathString]
+            args += try ["-L", defaultBuildParameters.toolchain.hostLibDir.pathString]
         }
         #endif
 

Sources/Build/BuildDescription/ResolvedModule+BuildDescription.swift

@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2015-2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import struct Basics.AbsolutePath
+import struct PackageGraph.ResolvedModule
+
+import SPMBuildCore
+
+extension ResolvedModule {
+    func tempsPath(_ buildParameters: BuildParameters) -> AbsolutePath {
+        let suffix = buildParameters.suffix(triple: self.buildTriple)
+        return buildParameters.buildPath.appending(component: "\(self.c99name)\(suffix).build")
+    }
+}