Detect native iframework dirs on macOS

This commit adds default search paths for system frameworks
on macOS while also adding `-isysroot` for OS versions at least BigSur.
Since BigSur (11.0.1), neither headers nor libs exist in standard
root locations (`/usr/include`, `/System/Library/Frameworks`). Instead, they
are now exclusively part of the installed developer toolchain (either
via XCode.app or CLT), and specifying `-isysroot` allows us to keep
using universal search paths such as `/System/Library/Frameworks` while
only changing the include flag from `-iframework` to
`-iframeworkwithsysroot`.

lib/std/zig/system.zig

@@ -22,13 +22,15 @@ pub const getSDKPath = macos.getSDKPath;
 pub const NativePaths = struct {
     include_dirs: ArrayList([:0]u8),
     lib_dirs: ArrayList([:0]u8),
+    framework_dirs: ArrayList([:0]u8),
     rpaths: ArrayList([:0]u8),
     warnings: ArrayList([:0]u8),
 
     pub fn detect(allocator: *Allocator) !NativePaths {
         var self: NativePaths = .{
             .include_dirs = ArrayList([:0]u8).init(allocator),
             .lib_dirs = ArrayList([:0]u8).init(allocator),
+            .framework_dirs = ArrayList([:0]u8).init(allocator),
             .rpaths = ArrayList([:0]u8).init(allocator),
             .warnings = ArrayList([:0]u8).init(allocator),
         };
@@ -88,6 +90,19 @@ pub const NativePaths = struct {
             return self;
         }
 
+        if (comptime Target.current.isDarwin()) {
+            try self.addIncludeDir("/usr/include");
+            try self.addIncludeDir("/usr/local/include");
+
+            try self.addLibDir("/usr/lib");
+            try self.addLibDir("/usr/local/lib");
+
+            try self.addFrameworkDir("/Library/Frameworks");
+            try self.addFrameworkDir("/System/Library/Frameworks");
+
+            return self;
+        }
+
         if (!is_windows) {
             const triple = try Target.current.linuxTriple(allocator);
             const qual = Target.current.cpu.arch.ptrBitWidth();
@@ -122,6 +137,7 @@ pub const NativePaths = struct {
     pub fn deinit(self: *NativePaths) void {
         deinitArray(&self.include_dirs);
         deinitArray(&self.lib_dirs);
+        deinitArray(&self.framework_dirs);
         deinitArray(&self.rpaths);
         deinitArray(&self.warnings);
         self.* = undefined;
@@ -158,6 +174,16 @@ pub const NativePaths = struct {
         return self.appendArray(&self.warnings, s);
     }
 
+    pub fn addFrameworkDir(self: *NativePaths, s: []const u8) !void {
+        return self.appendArray(&self.framework_dirs, s);
+    }
+
+    pub fn addFrameworkDirFmt(self: *NativePaths, comptime fmt: []const u8, args: anytype) !void {
+        const item = try std.fmt.allocPrint0(self.framework_dirs.allocator, fmt, args);
+        errdefer self.framework_dirs.allocator.free(item);
+        try self.framework_dirs.append(item);
+    }
+
     pub fn addWarningFmt(self: *NativePaths, comptime fmt: []const u8, args: anytype) !void {
         const item = try std.fmt.allocPrint0(self.warnings.allocator, fmt, args);
         errdefer self.warnings.allocator.free(item);
@@ -237,8 +263,7 @@ pub const NativeTargetInfo = struct {
                     //   `---` `` ``--> Sub-version (Starting from Windows 10 onwards)
                     //     \    `--> Service pack (Always zero in the constants defined)
                     //      `--> OS version (Major & minor)
-                    const os_ver: u16 =
-                        @intCast(u16, version_info.dwMajorVersion & 0xff) << 8 |
+                    const os_ver: u16 = @intCast(u16, version_info.dwMajorVersion & 0xff) << 8 |
                         @intCast(u16, version_info.dwMinorVersion & 0xff);
                     const sp_ver: u8 = 0;
                     const sub_ver: u8 = if (os_ver >= 0x0A00) subver: {

src/Compilation.zig

@@ -2079,12 +2079,6 @@ pub fn addCCArgs(
         try argv.append("-ffunction-sections");
     }
 
-    try argv.ensureCapacity(argv.items.len + comp.bin_file.options.framework_dirs.len * 2);
-    for (comp.bin_file.options.framework_dirs) |framework_dir| {
-        argv.appendAssumeCapacity("-iframework");
-        argv.appendAssumeCapacity(framework_dir);
-    }
-
     if (comp.bin_file.options.link_libcpp) {
         const libcxx_include_path = try std.fs.path.join(arena, &[_][]const u8{
             comp.zig_lib_directory.path.?, "libcxx", "include",
@@ -2894,6 +2888,7 @@ fn buildOutputFromZig(
         .directory = null, // Put it in the cache directory.
         .basename = bin_basename,
     };
+
     const sub_compilation = try Compilation.create(comp.gpa, .{
         .global_cache_directory = comp.global_cache_directory,
         .local_cache_directory = comp.global_cache_directory,

src/main.zig

@@ -1436,11 +1436,35 @@ fn buildOutputType(
         for (paths.warnings.items) |warning| {
             warn("{}", .{warning});
         }
+
+        const has_sysroot = if (comptime std.Target.current.isDarwin()) outer: {
+            const at_least_big_sur = target_info.target.os.getVersionRange().semver.min.major >= 11;
+            if (at_least_big_sur) {
+                const sdk_path = try std.zig.system.getSDKPath(arena);
+                try clang_argv.ensureCapacity(clang_argv.items.len + 2);
+                clang_argv.appendAssumeCapacity("-isysroot");
+                clang_argv.appendAssumeCapacity(sdk_path);
+                break :outer true;
+            }
+            break :outer false;
+        } else false;
+
         try clang_argv.ensureCapacity(clang_argv.items.len + paths.include_dirs.items.len * 2);
+        const isystem_flag = if (has_sysroot) "-iwithsysroot" else "-isystem";
         for (paths.include_dirs.items) |include_dir| {
-            clang_argv.appendAssumeCapacity("-isystem");
+            clang_argv.appendAssumeCapacity(isystem_flag);
             clang_argv.appendAssumeCapacity(include_dir);
         }
+
+        try clang_argv.ensureCapacity(clang_argv.items.len + paths.framework_dirs.items.len * 2);
+        try framework_dirs.ensureCapacity(framework_dirs.items.len + paths.framework_dirs.items.len);
+        const iframework_flag = if (has_sysroot) "-iframeworkwithsysroot" else "-iframework";
+        for (paths.framework_dirs.items) |framework_dir| {
+            clang_argv.appendAssumeCapacity(iframework_flag);
+            clang_argv.appendAssumeCapacity(framework_dir);
+            framework_dirs.appendAssumeCapacity(framework_dir);
+        }
+
         for (paths.lib_dirs.items) |lib_dir| {
             try lib_dirs.append(lib_dir);
         }