Cleanup some unnecessary build setting

- fix adding -lc++ to OTHER_LDFLAGS to match native build system.

Author: daveinglis

Fixtures/PIFBuilder/CCPackage/Package.swift

@@ -0,0 +1,14 @@
+// swift-tools-version: 6.2
+
+import PackageDescription
+
+let package = Package(
+    name: "CCPackage",
+    products: [
+        .library(name: "CCTarget", type: .static, targets: ["CCTarget"]),
+    ],
+    targets: [
+        .target(name: "CCTarget", ),
+        .executableTarget(name: "executable", dependencies: ["CCTarget"]),
+    ]
+)

Fixtures/PIFBuilder/CCPackage/Sources/CCTarget/include/test.h

@@ -0,0 +1,2 @@
+
+#include <string>

Fixtures/PIFBuilder/CCPackage/Sources/CCTarget/test.cc

@@ -0,0 +1,2 @@
+
+#include <test.h>

Fixtures/PIFBuilder/CCPackage/Sources/executable/executable.swift

@@ -0,0 +1,9 @@
+// The Swift Programming Language
+// https://docs.swift.org/swift-book
+
+@main
+struct Executable {
+    static func main() {
+        print("Hello, world!")
+    }
+}

Fixtures/PIFBuilder/UnknownPlatforms/Package.swift

@@ -9,7 +9,7 @@ let package = Package(
             name: "UnknownPlatforms",
             swiftSettings: [
                 .define("FOO", .when(platforms: [.custom("DoesNotExist")])),
-		.define("BAR", .when(platforms: [.linux])),
+		        .define("BAR", .when(platforms: [.linux])),
                 .define("BAZ", .when(platforms: [.macOS])),
             ],
         ),

Sources/SwiftBuildSupport/PackagePIFBuilder.swift

@@ -552,6 +552,9 @@ public final class PackagePIFBuilder {
         // We currently deliberately do not support Swift ObjC interface headers.
         settings[.SWIFT_INSTALL_OBJC_HEADER] = "NO"
         settings[.SWIFT_OBJC_INTERFACE_HEADER_NAME] = ""
+        
+        // rdar://47937899 (Don't try to link frameworks to object files) 
+        //  - looks like this defaults to OTHER_LDFLAGS (via xcspec) which can result in linking frameworks to mh_objects which is unwanted.
         settings[.OTHER_LDRFLAGS] = []
 
         // Packages use the SwiftPM workspace's cache directory as a compiler working directory to maximize module

Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift

@@ -484,14 +484,16 @@ extension PackagePIFProjectBuilder {
         if enableDuplicateLinkageCulling {
             impartedSettings[.LD_WARN_DUPLICATE_LIBRARIES] = "NO"
         }
-        impartedSettings[.OTHER_LDFLAGS] = (sourceModule.isCxx ? ["-lc++"] : []) + ["$(inherited)"]
-        impartedSettings[.OTHER_LDRFLAGS] = []
-        log(
-            .debug,
-            indent: 1,
-            "Added '\(impartedSettings[.OTHER_LDFLAGS]!)' to imparted OTHER_LDFLAGS"
-        )
-
+        if sourceModule.isCxx {
+            for platform in ProjectModel.BuildSettings.Platform.allCases {
+                // darwin & freebsd
+                if [.macOS, .macCatalyst, .iOS, .watchOS, .tvOS, .xrOS, .driverKit, .freebsd].contains(platform) {
+                    settings[.OTHER_LDFLAGS, platform] = ["-lc++", "$(inherited)"]
+                } else if [.android, .linux, .wasi, .openbsd].contains(platform) {
+                    settings[.OTHER_LDFLAGS, platform] = ["-lstdc++", "$(inherited)"]
+                }
+            }
+        }
         // This should be only for dynamic targets, but that isn't possible today.
         // Improvement is tracked by rdar://77403529 (Only impart `PackageFrameworks` search paths to clients of dynamic
         // package targets and products).
@@ -816,7 +818,6 @@ extension PackagePIFProjectBuilder {
         impartedSettings[.OTHER_CFLAGS] = ["-fmodule-map-file=\(systemLibrary.modulemapFileAbsolutePath)"] +
             pkgConfig.cFlags.prepending("$(inherited)")
         impartedSettings[.OTHER_LDFLAGS] = pkgConfig.libs.prepending("$(inherited)")
-        impartedSettings[.OTHER_LDRFLAGS] = []
         impartedSettings[.OTHER_SWIFT_FLAGS] = ["-Xcc"] + impartedSettings[.OTHER_CFLAGS]!
         log(.debug, indent: 1, "Added '\(systemLibrary.path.pathString)' to imparted HEADER_SEARCH_PATHS")
 

Tests/SwiftBuildSupportTests/PIFBuilderTests.swift

@@ -85,6 +85,19 @@ extension SwiftBuildSupport.PIF.Workspace {
 }
 
 extension SwiftBuildSupport.PIF.Project {
+    fileprivate func target(id: String) throws -> ProjectModel.BaseTarget {
+        let matchingTargets: [ProjectModel.BaseTarget] = underlying.targets.filter {
+            return $0.common.id.value == String(id)
+        }
+        if matchingTargets.isEmpty {
+            throw StringError("No target named \(id) in PIF project")
+        } else if matchingTargets.count > 1 {
+            throw StringError("Multiple target named \(id) in PIF project")
+        } else {
+            return matchingTargets[0]
+        }
+    }
+
     fileprivate func target(named name: String) throws -> ProjectModel.BaseTarget {
         let matchingTargets = underlying.targets.filter {
             $0.common.name == name
@@ -135,6 +148,28 @@ struct PIFBuilderTests {
         }
     }
 
+    @Test func platformCCLibrary() async throws {
+        try await withGeneratedPIF(fromFixture: "PIFBuilder/CCPackage") { pif, observabilitySystem in
+            let releaseConfig = try pif.workspace
+                .project(named: "CCPackage")
+                .target(id: "PACKAGE-TARGET:CCTarget")
+                .buildConfig(named: "Release")
+
+            for platform in ProjectModel.BuildSettings.Platform.allCases {
+                let ld_flags = releaseConfig.settings[.OTHER_LDFLAGS, platform]
+                if [.macOS, .macCatalyst, .iOS, .watchOS, .tvOS, .xrOS, .driverKit, .freebsd].contains(platform) {
+                     #expect(ld_flags == ["-lc++", "$(inherited)"], "for platform \(platform)")
+                } else if [.android, .linux, .wasi, .openbsd].contains(platform) {
+                    #expect(ld_flags == ["-lstdc++", "$(inherited)"], "for platform \(platform)")                    
+                } else if [.windows, ._iOSDevice].contains(platform) {
+                    #expect(ld_flags == nil, "for platform \(platform)")
+                } else {
+                    Issue.record("Unexpected platform \(platform)")
+                }
+            }
+        }
+    }
+
     @Test func pluginWithBinaryTargetDependency() async throws {
         try await withGeneratedPIF(fromFixture: "Miscellaneous/Plugins/BinaryTargetExePlugin") { pif, observabilitySystem in
             // Verify that PIF generation succeeds for a package with a plugin that depends on a binary target