zig/src-self-hosted/link/MachO.zig

const MachO = @This();

const std = @import("std");
const Allocator = std.mem.Allocator;
const assert = std.debug.assert;
const fs = std.fs;
const log = std.log;
const macho = std.macho;

const Module = @import("../Module.zig");
const link = @import("../link.zig");
const File = link.File;

pub const base_tag: Tag = File.Tag.macho;

base: File,

entry_addr: ?u64 = null,

error_flags: File.ErrorFlags = File.ErrorFlags{},

pub const TextBlock = struct {
    pub const empty = TextBlock{};
};

pub const SrcFn = struct {
    pub const empty = SrcFn{};
};

pub fn openPath(allocator: *Allocator, dir: fs.Dir, sub_path: []const u8, options: link.Options) !*File {
    assert(options.object_format == .macho);

    const file = try dir.createFile(sub_path, .{ .truncate = false, .read = true, .mode = link.determineMode(options) });
    errdefer file.close();

    var macho_file = try allocator.create(MachO);
    errdefer allocator.destroy(macho_file);

    macho_file.* = openFile(allocator, file, options) catch |err| switch (err) {
        error.IncrFailed => try createFile(allocator, file, options),
        else => |e| return e,
    };

    return &macho_file.base;
}

/// Returns error.IncrFailed if incremental update could not be performed.
fn openFile(allocator: *Allocator, file: fs.File, options: link.Options) !MachO {
    switch (options.output_mode) {
        .Exe => {},
        .Obj => {},
        .Lib => return error.IncrFailed,
    }
    var self: MachO = .{
        .base = .{
            .file = file,
            .tag = .macho,
            .options = options,
            .allocator = allocator,
        },
    };
    errdefer self.deinit();

    // TODO implement reading the macho file
    return error.IncrFailed;
    //try self.populateMissingMetadata();
    //return self;
}

/// Truncates the existing file contents and overwrites the contents.
/// Returns an error if `file` is not already open with +read +write +seek abilities.
fn createFile(allocator: *Allocator, file: fs.File, options: link.Options) !MachO {
    switch (options.output_mode) {
        .Exe => {},
        .Obj => {},
        .Lib => return error.TODOImplementWritingLibFiles,
    }

    var self: MachO = .{
        .base = .{
            .file = file,
            .tag = .macho,
            .options = options,
            .allocator = allocator,
        },
    };
    errdefer self.deinit();

    return self;
}

fn writeMachOHeader(self: *MachO) !void {
    var hdr: macho.mach_header_64 = undefined;
    hdr.magic = macho.MH_MAGIC_64;

    const CpuInfo = struct {
        cpu_type: macho.cpu_type_t,
        cpu_subtype: macho.cpu_subtype_t,
    };

    const cpu_info: CpuInfo = switch (self.base.options.target.cpu.arch) {
        .aarch64 => .{
            .cpu_type = macho.CPU_TYPE_ARM64,
            .cpu_subtype = macho.CPU_SUBTYPE_ARM_ALL,
        },
        .x86_64 => .{
            .cpu_type = macho.CPU_TYPE_X86_64,
            .cpu_subtype = macho.CPU_SUBTYPE_X86_64_ALL,
        },
        else => return error.UnsupportedMachOArchitecture,
    };
    hdr.cputype = cpu_info.cpu_type;
    hdr.cpusubtype = cpu_info.cpu_subtype;

    const filetype: u32 = switch (self.base.options.output_mode) {
        .Exe => macho.MH_EXECUTE,
        .Obj => macho.MH_OBJECT,
        .Lib => switch (self.base.options.link_mode) {
            .Static => return error.TODOStaticLibMachOType,
            .Dynamic => macho.MH_DYLIB,
        },
    };
    hdr.filetype = filetype;

    // TODO the rest of the header
    hdr.ncmds = 0;
    hdr.sizeofcmds = 0;
    hdr.flags = 0;
    hdr.reserved = 0;

    try self.base.file.?.pwriteAll(@ptrCast([*]const u8, &hdr)[0..@sizeOf(macho.mach_header_64)], 0);
}

pub fn flush(self: *MachO, module: *Module) !void {
    // TODO implement flush
    if (self.entry_addr == null and self.base.options.output_mode == .Exe) {
        log.debug("flushing. no_entry_point_found = true\n", .{});
        self.error_flags.no_entry_point_found = true;
    } else {
        log.debug("flushing. no_entry_point_found = false\n", .{});
        self.error_flags.no_entry_point_found = false;
        try self.writeMachOHeader();
    }
}

pub fn deinit(self: *MachO) void {}

pub fn allocateDeclIndexes(self: *MachO, decl: *Module.Decl) !void {}

pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {}

pub fn updateDeclLineNumber(self: *MachO, module: *Module, decl: *const Module.Decl) !void {}

pub fn updateDeclExports(
    self: *MachO,
    module: *Module,
    decl: *const Module.Decl,
    exports: []const *Module.Export,
) !void {}

pub fn freeDecl(self: *MachO, decl: *Module.Decl) void {}