build: LipoStep

build.zig

@@ -21,6 +21,7 @@ const zlib = @import("pkg/zlib/build.zig");
 const tracylib = @import("pkg/tracy/build.zig");
 const system_sdk = @import("vendor/mach/libs/glfw/system_sdk.zig");
 const WasmTarget = @import("src/os/wasm/target.zig").Target;
+const LipoStep = @import("src/build/LipoStep.zig");
 const XCFrameworkStep = @import("src/build/XCFrameworkStep.zig");
 
 // Do a comptime Zig version requirement. The required Zig version is
@@ -133,28 +134,57 @@ pub fn build(b: *std.build.Builder) !void {
     }
 
     // c lib
-    const static_lib = lib: {
+    {
         const static_lib = b.addStaticLibrary("ghostty", "src/main_c.zig");
         static_lib.setBuildMode(mode);
         static_lib.setTarget(target);
         static_lib.install();
         static_lib.linkLibC();
         b.default_step.dependOn(&static_lib.step);
-        break :lib static_lib;
-    };
+    }
 
     // On Mac we can build the app.
-    const macapp = b.step("macapp", "Build macOS app");
+    const macapp = b.step("macapp", "Build macOS app using XCode.");
     if (builtin.target.isDarwin()) {
+        const static_lib_aarch64 = lib: {
+            const lib = b.addStaticLibrary("ghostty", "src/main_c.zig");
+            lib.setBuildMode(mode);
+            lib.setTarget(try std.zig.CrossTarget.parse(.{ .arch_os_abi = "aarch64-macos" }));
+            lib.install();
+            lib.linkLibC();
+            b.default_step.dependOn(&lib.step);
+            break :lib lib;
+        };
+
+        const static_lib_x86_64 = lib: {
+            const lib = b.addStaticLibrary("ghostty", "src/main_c.zig");
+            lib.setBuildMode(mode);
+            lib.setTarget(try std.zig.CrossTarget.parse(.{ .arch_os_abi = "x86_64-macos" }));
+            lib.install();
+            lib.linkLibC();
+            b.default_step.dependOn(&lib.step);
+            break :lib lib;
+        };
+
+        const static_lib_universal = LipoStep.create(b, .{
+            .name = "ghostty",
+            .out_name = "libghostty.a",
+            .input_a = .{ .generated = &static_lib_aarch64.output_path_source },
+            .input_b = .{ .generated = &static_lib_x86_64.output_path_source },
+        });
+        static_lib_universal.step.dependOn(&static_lib_aarch64.step);
+        static_lib_universal.step.dependOn(&static_lib_x86_64.step);
+
         // The xcframework wraps our ghostty library so that we can link
         // it to the final app built with Swift.
         const xcframework = XCFrameworkStep.create(b, .{
             .name = "GhosttyKit",
             .out_path = "macos/GhosttyKit.xcframework",
-            .library = .{ .generated = &static_lib.output_lib_path_source },
+            .library = .{ .generated = &static_lib_universal.out_path },
             .headers = .{ .path = "include" },
         });
-        xcframework.step.dependOn(&static_lib.step);
+        xcframework.step.dependOn(&static_lib_universal.step);
+        b.default_step.dependOn(&xcframework.step);
         macapp.dependOn(&xcframework.step);
     }
 

macos/.gitignore

@@ -1,4 +1,5 @@
 .DS_Store
 /*.xcframework
+build/
 xcuserdata/
 DerivedData/

src/build/LipoStep.zig

@@ -0,0 +1,75 @@
+//! A zig builder step that runs "lipo" on two binaries to create
+//! a universal binary.
+const LipoStep = @This();
+
+const std = @import("std");
+const Step = std.build.Step;
+const FileSource = std.build.FileSource;
+const GeneratedFile = std.build.GeneratedFile;
+
+pub const Options = struct {
+    /// The name of the xcframework to create.
+    name: []const u8,
+
+    /// The filename (not the path) of the file to create.
+    out_name: []const u8,
+
+    /// Library file (dylib, a) to package.
+    input_a: FileSource,
+    input_b: FileSource,
+};
+
+step: Step,
+builder: *std.build.Builder,
+
+/// Resulting binary
+out_path: GeneratedFile,
+
+/// See Options
+name: []const u8,
+out_name: []const u8,
+input_a: FileSource,
+input_b: FileSource,
+
+pub fn create(builder: *std.build.Builder, opts: Options) *LipoStep {
+    const self = builder.allocator.create(LipoStep) catch @panic("OOM");
+    self.* = .{
+        .step = Step.init(.custom, builder.fmt("lipo {s}", .{opts.name}), builder.allocator, make),
+        .builder = builder,
+        .name = opts.name,
+        .out_path = .{ .step = &self.step },
+        .out_name = opts.out_name,
+        .input_a = opts.input_a,
+        .input_b = opts.input_b,
+    };
+    return self;
+}
+
+fn make(step: *Step) !void {
+    const self = @fieldParentPtr(LipoStep, "step", step);
+
+    // TODO: use the zig cache system when it is in the stdlib
+    // https://github.com/ziglang/zig/pull/14571
+    const output_path = self.builder.pathJoin(&.{
+        self.builder.cache_root, self.out_name,
+    });
+
+    // We use a RunStep here to ease our configuration.
+    {
+        const run = std.build.RunStep.create(self.builder, self.builder.fmt(
+            "lipo {s}",
+            .{self.name},
+        ));
+        run.addArgs(&.{
+            "lipo",
+            "-create",
+            "-output",
+            output_path,
+            self.input_a.getPath(self.builder),
+            self.input_b.getPath(self.builder),
+        });
+        try run.step.make();
+    }
+
+    self.out_path.path = output_path;
+}