build: support native freestanding libghostty-vt

Native freestanding targets cannot emit shared libraries and do not provide an OS page size, stack unwinder, hosted SIMD dependencies, or filesystem-backed Kitty graphics. Build only the static artifact for those targets, define the minimum alignment used for terminal pages, disable hosted-only defaults, and install the public headers with the archive.

build.zig

@@ -125,26 +125,36 @@ pub fn build(b: *std.Build) !void {
     }
 
     // libghostty-vt
-    const libghostty_vt_shared = shared: {
+    const native_freestanding = config.target.result.os.tag == .freestanding and
+        !config.target.result.cpu.arch.isWasm();
+    const libghostty_vt_shared: ?buildpkg.GhosttyLibVt = shared: {
         if (config.target.result.cpu.arch.isWasm()) {
             break :shared try buildpkg.GhosttyLibVt.initWasm(
                 b,
                 &mod,
             );
         }
+        if (native_freestanding) break :shared null;
 
         break :shared try buildpkg.GhosttyLibVt.initShared(
             b,
             &mod,
         );
     };
-    libghostty_vt_shared.install(b.getInstallStep());
+    if (libghostty_vt_shared) |shared| {
+        shared.install(b.getInstallStep());
 
-    const type_schema_test = b.addSystemCommand(&.{"python3"});
-    type_schema_test.addFileArg(b.path("src/terminal/c/types-schema-verify.py"));
-    type_schema_test.addFileArg(b.path("src/terminal/c/types.schema.json"));
-    type_schema_test.addFileArg(libghostty_vt_shared.output);
-    test_lib_vt_schema_step.dependOn(&type_schema_test.step);
+        const type_schema_test = b.addSystemCommand(&.{"python3"});
+        type_schema_test.addFileArg(b.path("src/terminal/c/types-schema-verify.py"));
+        type_schema_test.addFileArg(b.path("src/terminal/c/types.schema.json"));
+        type_schema_test.addFileArg(shared.output);
+        test_lib_vt_schema_step.dependOn(&type_schema_test.step);
+    } else {
+        try test_lib_vt_schema_step.addError(
+            "cannot execute the ABI manifest for a native freestanding target",
+            .{},
+        );
+    }
 
     // libghostty-vt static lib
     const libghostty_vt_static = try buildpkg.GhosttyLibVt.initStatic(
@@ -167,6 +177,15 @@ pub fn build(b: *std.Build) !void {
             libghostty_vt_static.output,
             static_lib_name,
         ).step);
+
+        if (native_freestanding) {
+            b.getInstallStep().dependOn(&b.addInstallDirectory(.{
+                .source_dir = b.path("include/ghostty"),
+                .install_dir = .header,
+                .install_subdir = "ghostty",
+                .include_extensions = &.{".h"},
+            }).step);
+        }
     }
 
     // libghostty-vt xcframework (Apple only, universal binary).

src/build/Config.zig

@@ -240,9 +240,10 @@ pub fn init(b: *std.Build, appVersion: []const u8, libVersion: []const u8) !Conf
         "simd",
         "Build with SIMD-accelerated code paths. Results in significant performance improvements.",
     ) orelse simd: {
-        // We can't build our SIMD dependencies for Wasm. Note that we may
-        // still use SIMD features in the Wasm-builds.
-        if (target.result.cpu.arch.isWasm()) break :simd false;
+        // We can't build our SIMD dependencies for Wasm or freestanding
+        // targets. Note that we may still use SIMD features in the Wasm-builds.
+        if (target.result.cpu.arch.isWasm() or
+            target.result.os.tag == .freestanding) break :simd false;
 
         break :simd true;
     };

src/build/GhosttyLibVt.zig

@@ -246,7 +246,9 @@ fn initLib(
 
         // Enable PIC so the static library can be linked into PIE
         // executables, which is the default on most Linux distributions.
-        lib.root_module.pic = true;
+        // Native freestanding targets don't have a dynamic loader and some,
+        // such as Xtensa, don't support PIC relocations.
+        lib.root_module.pic = target.result.os.tag != .freestanding;
     }
 
     if (target.result.os.tag == .windows) {

src/lib_vt.zig

@@ -424,6 +424,15 @@ comptime {
 pub const std_options: std.Options = opts: {
     var options: std.Options = .{};
 
+    if (native_freestanding) {
+        // Freestanding targets don't have an OS page size. We still need an
+        // alignment for terminal page allocations, and 16 covers everything
+        // stored in a page without requiring 4 KiB-aligned embedded heaps.
+        options.page_size_min = 16;
+        options.page_size_max = 16;
+        options.allow_stack_tracing = false;
+    }
+
     if (builtin.target.cpu.arch.isWasm()) {
         // In non-debug modes, we want to ship effectively no logging
         // warn and lower add ~200KB at the time of this comment.
@@ -464,10 +473,14 @@ pub const std_options: std.Options = opts: {
 /// traces on panic, std.debug.print, etc.). These builds are for
 /// development, where the roughly 160KB of binary size it costs is
 /// worth it.
-const debug_machinery: bool = builtin.is_test or switch (builtin.mode) {
-    .Debug, .ReleaseSafe => true,
-    .ReleaseFast, .ReleaseSmall => false,
-};
+const native_freestanding = builtin.target.os.tag == .freestanding and
+    !builtin.target.cpu.arch.isWasm();
+
+const debug_machinery: bool = !native_freestanding and
+    (builtin.is_test or switch (builtin.mode) {
+        .Debug, .ReleaseSafe => true,
+        .ReleaseFast, .ReleaseSmall => false,
+    });
 
 /// The panic handler for when this file is the root module.
 ///

src/terminal/build_options.zig

@@ -263,8 +263,7 @@ pub const Options = struct {
     /// targets, so it is always disabled there regardless of the
     /// feature setting.
     pub fn kittyGraphics(self: Options, target: std.Target) bool {
-        if (target.cpu.arch == .wasm32 and target.os.tag == .freestanding)
-            return false;
+        if (target.os.tag == .freestanding) return false;
         return self.features.kitty_graphics;
     }