Merge pull request #6932 from kubkon/fix-6318

macOS: fix linking issues on BigSur

lib/std/zig/system.zig

@@ -17,6 +17,8 @@ const macos = @import("system/macos.zig");
 
 const is_windows = Target.current.os.tag == .windows;
 
+pub const getSDKPath = macos.getSDKPath;
+
 pub const NativePaths = struct {
     include_dirs: ArrayList([:0]u8),
     lib_dirs: ArrayList([:0]u8),

lib/std/zig/system/macos.zig

@@ -4,6 +4,8 @@
 // The MIT license requires this copyright notice to be included in all copies
 // and substantial portions of the software.
 const std = @import("std");
+const assert = std.debug.assert;
+const mem = std.mem;
 
 pub fn version_from_build(build: []const u8) !std.builtin.Version {
     // build format:
@@ -452,3 +454,25 @@ test "version_from_build" {
         std.testing.expect(std.mem.eql(u8, sver, pair[1]));
     }
 }
+
+/// Detect SDK path on Darwin.
+/// Calls `xcrun --show-sdk-path` which result can be used to specify
+/// `-syslibroot` param of the linker.
+/// The caller needs to free the resulting path slice.
+pub fn getSDKPath(allocator: *mem.Allocator) ![]u8 {
+    assert(std.Target.current.isDarwin());
+    const argv = &[_][]const u8{ "xcrun", "--show-sdk-path" };
+    const result = try std.ChildProcess.exec(.{ .allocator = allocator, .argv = argv });
+    defer {
+        allocator.free(result.stderr);
+        allocator.free(result.stdout);
+    }
+    if (result.stderr.len != 0) {
+        std.log.err("unexpected 'xcrun --show-sdk-path' stderr: {}", .{result.stderr});
+    }
+    if (result.term.Exited != 0) {
+        return error.ProcessTerminated;
+    }
+    const syslibroot = mem.trimRight(u8, result.stdout, "\r\n");
+    return mem.dupe(allocator, u8, syslibroot);
+}

src/Compilation.zig

@@ -472,6 +472,14 @@ pub fn create(gpa: *Allocator, options: InitOptions) !*Compilation {
             break :blk false;
         };
 
+        const syslibroot = if (build_options.have_llvm and comptime std.Target.current.isDarwin()) outer: {
+            const path = if (use_lld and options.is_native_os and options.target.isDarwin()) inner: {
+                const syslibroot_path = try std.zig.system.getSDKPath(arena);
+                break :inner syslibroot_path;
+            } else null;
+            break :outer path;
+        } else null;
+
         const link_libc = options.link_libc or target_util.osRequiresLibC(options.target);
 
         const must_dynamic_link = dl: {
@@ -773,6 +781,7 @@ pub fn create(gpa: *Allocator, options: InitOptions) !*Compilation {
             .frameworks = options.frameworks,
             .framework_dirs = options.framework_dirs,
             .system_libs = system_libs,
+            .syslibroot = syslibroot,
             .lib_dirs = options.lib_dirs,
             .rpath_list = options.rpath_list,
             .strip = strip,

src/link.zig

@@ -88,6 +88,8 @@ pub const Options = struct {
     llvm_cpu_features: ?[*:0]const u8,
     /// Extra args passed directly to LLD. Ignored when not linking with LLD.
     extra_lld_args: []const []const u8,
+    /// Darwin-only. Set the root path to the system libraries and frameworks.
+    syslibroot: ?[]const u8,
 
     objects: []const []const u8,
     framework_dirs: []const []const u8,

src/link/MachO.zig

@@ -628,6 +628,11 @@ fn linkWithLLD(self: *MachO, comp: *Compilation) !void {
             }
         }
 
+        if (self.base.options.syslibroot) |dir| {
+            try argv.append("-syslibroot");
+            try argv.append(dir);
+        }
+
         for (self.base.options.lib_dirs) |lib_dir| {
             try argv.append("-L");
             try argv.append(lib_dir);