diff --git a/bootstrap/Compilation.zig b/bootstrap/Compilation.zig
index 3aa88d5..f4c7dce 100644
--- a/bootstrap/Compilation.zig
+++ b/bootstrap/Compilation.zig
@@ -1360,7 +1360,7 @@ pub fn log(comptime logger_scope: LoggerScope, logger: getLoggerScopeType(logger
 }
 
 pub fn panic(message: []const u8, stack_trace: ?*std.builtin.StackTrace, return_address: ?usize) noreturn {
-    const print_stack_trace = false;
+    const print_stack_trace = true;
     switch (print_stack_trace) {
         true => @call(.always_inline, std.builtin.default_panic, .{ message, stack_trace, return_address }),
         false => {
diff --git a/bootstrap/backend/c_transpiler.zig b/bootstrap/backend/c_transpiler.zig
index 7371899..518a952 100644
--- a/bootstrap/backend/c_transpiler.zig
+++ b/bootstrap/backend/c_transpiler.zig
@@ -38,7 +38,7 @@ pub const TranslationUnit = struct {
     enum_type_set: AutoArrayHashMap(Compilation.Type.Index, []const u8) = .{},
     declaration_set: AutoArrayHashMap(Compilation.Declaration.Index, []const u8) = .{},
 
-    const SyscallBitset = std.StaticBitSet(6);
+    const SyscallBitset = std.StaticBitSet(7);
 
     fn create(module: *Module, allocator: Allocator) !*TranslationUnit {
         var unit = try allocator.create(TranslationUnit);
@@ -645,12 +645,14 @@ pub const TranslationUnit = struct {
                 try list.append(allocator, '_');
                 try list.appendSlice(allocator, enum_field_name);
 
-                try list.appendSlice(allocator, " = ");
+                if (!enum_field.value.invalid) {
+                    try list.appendSlice(allocator, " = ");
 
-                try unit.writeValue(module, &list, allocator, Compilation.Type.Index.invalid, 0, .{
-                    .value_index = enum_field.value,
-                    .type_index = Compilation.Type.usize,
-                });
+                    try unit.writeValue(module, &list, allocator, Compilation.Type.Index.invalid, 0, .{
+                        .value_index = enum_field.value,
+                        .type_index = Compilation.Type.usize,
+                    });
+                }
 
                 try list.appendSlice(allocator, ",\n");
             }
@@ -795,7 +797,7 @@ pub const TranslationUnit = struct {
         const syscall = module.values.syscalls.get(syscall_index);
         const arguments = syscall.getArguments();
 
-        if (!unit.syscall_bitset.isSet(arguments.len - 1)) {
+        if (!unit.syscall_bitset.isSet(arguments.len)) {
             try unit.function_declarations.appendSlice(allocator, "static __inline u64 syscall");
             try unit.function_declarations.writer(allocator).print("{}(", .{arguments.len});
             try unit.function_declarations.appendSlice(allocator, "u64 n, ");
@@ -849,7 +851,7 @@ pub const TranslationUnit = struct {
                 \\
             );
 
-            unit.syscall_bitset.set(arguments.len - 1);
+            unit.syscall_bitset.set(arguments.len);
         }
 
         try list.writer(allocator).print("syscall{}(", .{arguments.len});
diff --git a/bootstrap/frontend/semantic_analyzer.zig b/bootstrap/frontend/semantic_analyzer.zig
index 40854ec..072c670 100644
--- a/bootstrap/frontend/semantic_analyzer.zig
+++ b/bootstrap/frontend/semantic_analyzer.zig
@@ -2631,6 +2631,7 @@ const Analyzer = struct {
 
                     break :blk switch (backing_type_token.id) {
                         .keyword_unsigned_integer => if (equal(u8, token_bytes, "u8")) Type.u8 else if (equal(u8, token_bytes, "u16")) Type.u16 else if (equal(u8, token_bytes, "u32")) Type.u32 else if (equal(u8, token_bytes, "u64")) Type.u64 else if (equal(u8, token_bytes, "usize")) Type.usize else unreachable,
+                        .fixed_keyword_usize => Type.usize,
                         else => |t| @panic(@tagName(t)),
                     };
                 }
@@ -2988,11 +2989,26 @@ const Analyzer = struct {
                             const backing_integer_type = analyzer.module.types.array.get(struct_type.backing_type);
                             if (backing_integer_type.integer.bit_count >> 3 <= flexible_integer.byte_count) {
                                 return .success;
+                            } else {
+                                unreachable;
                             }
                         }
 
                         unreachable;
                     },
+                    .@"enum" => |enum_index| {
+                        const enum_type = analyzer.module.types.enums.get(enum_index);
+                        if (!enum_type.backing_type.invalid) {
+                            const backing_integer_type = analyzer.module.types.array.get(enum_type.backing_type);
+                            if (backing_integer_type.integer.bit_count >> 3 <= flexible_integer.byte_count) {
+                                return .success;
+                            } else {
+                                unreachable;
+                            }
+                        } else {
+                            unreachable;
+                        }
+                    },
                     else => |t| @panic(@tagName(t)),
                 };
             },
@@ -3007,6 +3023,7 @@ const Analyzer = struct {
                         .integer => |integer| switch (destination_type.*) {
                             .optional => |optional| switch (analyzer.module.types.array.get(optional.element_type).*) {
                                 .pointer => if (integer.bit_count == 64) .success else unreachable,
+                                .integer => .cast_to_optional,
                                 else => |t| @panic(@tagName(t)),
                             },
                             .integer => .success,
@@ -3478,30 +3495,33 @@ const Analyzer = struct {
                 assert(expect_type != .none);
                 const cast_result = try analyzer.canCast(expect_type, value_type);
 
-                if (cast_result == .success) {
-                    const cast_index = try analyzer.module.values.casts.append(analyzer.allocator, .{
-                        .value = value_to_cast_index,
-                        .type = switch (expect_type) {
-                            .none => unreachable,
-                            .flexible_integer => |flexible_integer| if (flexible_integer.sign) |sign| switch (sign) {
-                                else => unreachable,
-                            } else switch (flexible_integer.byte_count) {
-                                1 => Type.u8,
-                                2 => Type.u16,
-                                4 => Type.u32,
-                                8 => Type.u64,
+                switch (cast_result) {
+                    inline .success, .cast_to_optional => |cast_type| {
+                        const cast_index = try analyzer.module.values.casts.append(analyzer.allocator, .{
+                            .value = value_to_cast_index,
+                            .type = switch (expect_type) {
+                                .none => unreachable,
+                                .flexible_integer => |flexible_integer| if (flexible_integer.sign) |sign| switch (sign) {
+                                    else => unreachable,
+                                } else switch (flexible_integer.byte_count) {
+                                    1 => Type.u8,
+                                    2 => Type.u16,
+                                    4 => Type.u32,
+                                    8 => Type.u64,
+                                    else => unreachable,
+                                },
+                                .type_index => |type_index| type_index,
                                 else => unreachable,
                             },
-                            .type_index => |type_index| type_index,
-                            else => unreachable,
-                        },
-                    });
+                        });
 
-                    break :blk Value{
-                        .cast = cast_index,
-                    };
-                } else {
-                    std.debug.panic("Can't cast", .{});
+                        break :blk @unionInit(Value, switch (cast_type) {
+                            .success => "cast",
+                            .cast_to_optional => "optional_cast",
+                            else => @compileError("WTF"),
+                        }, cast_index);
+                    },
+                    else => @panic("can't cast"),
                 }
             },
         };
diff --git a/bootstrap/frontend/syntactic_analyzer.zig b/bootstrap/frontend/syntactic_analyzer.zig
index f7884f7..edce878 100644
--- a/bootstrap/frontend/syntactic_analyzer.zig
+++ b/bootstrap/frontend/syntactic_analyzer.zig
@@ -1565,6 +1565,13 @@ const Analyzer = struct {
             .fixed_keyword_enum => blk: {
                 analyzer.token_i += 1;
 
+                // TODO: is this the best way?
+                if (analyzer.tokens[analyzer.token_i].id == .left_parenthesis) {
+                    analyzer.token_i += 1;
+                    assert(analyzer.tokens[analyzer.token_i + 1].id == .right_parenthesis);
+                    analyzer.token_i += 2;
+                }
+
                 _ = try analyzer.expectToken(.left_brace);
                 const node_list = try analyzer.containerMembers(.@"enum");
                 _ = try analyzer.expectToken(.right_brace);
diff --git a/lib/std/build.nat b/lib/std/build.nat
new file mode 100644
index 0000000..cd25921
--- /dev/null
+++ b/lib/std/build.nat
@@ -0,0 +1,7 @@
+const std = #import("std");
+const Target = std.Target;
+
+const Executable = struct{
+    target: Target,
+    main_source_path: []const u8,
+};
diff --git a/lib/std/builtin.nat b/lib/std/builtin.nat
index 7c41626..924d084 100644
--- a/lib/std/builtin.nat
+++ b/lib/std/builtin.nat
@@ -2,10 +2,10 @@ const Os = enum{
     linux,
     macos,
     windows,
+    freestanding,
 };
 
 const Cpu = enum{
-    aarch64,
     x86_64,
 };
 
diff --git a/lib/std/os.nat b/lib/std/os.nat
index 014c85b..3ec2a96 100644
--- a/lib/std/os.nat
+++ b/lib/std/os.nat
@@ -18,6 +18,8 @@ const exit = fn(exit_code: s32) noreturn {
     unreachable;
 }
 
+const ProcessId = system.ProcessId;
+
 const ProtectionFlags = struct(u32){
     read: bool,
     write: bool,
@@ -99,6 +101,19 @@ const current_executable_path = fn(allocator: &Allocator) ?[]u8 {
     }
 }
 
+const duplicate_process = fn () ?ProcessId {
+    switch (current) {
+        .linux =>  {
+            if (linux.unwrapSyscall(syscall_result = linux.fork())) |fork_result| {
+                return #cast(fork_result);
+            } else {
+                return null;
+            }
+        },
+        else => #error("OS not supported"),
+    }
+}
+
 const FileDescriptor = struct{
     handle: system.FileDescriptor,
 
diff --git a/lib/std/os/linux.nat b/lib/std/os/linux.nat
index 946aa66..1d7aeb4 100644
--- a/lib/std/os/linux.nat
+++ b/lib/std/os/linux.nat
@@ -4,6 +4,379 @@ const stdin: FileDescriptor = 0;
 const stdout: FileDescriptor = 1;
 const stderr: FileDescriptor = 2;
 
+const Syscall = switch (#import("builtin").cpu) {
+    .x86_64 => Syscall_x86_64,
+    else => #error("Architecture not supported"),
+};
+
+const ProcessId = s32;
+
+const Syscall_x86_64 = enum(usize) {
+    read = 0,
+    write = 1,
+    open = 2,
+    close = 3,
+    stat = 4,
+    fstat = 5,
+    lstat = 6,
+    poll = 7,
+    lseek = 8,
+    mmap = 9,
+    mprotect = 10,
+    munmap = 11,
+    brk = 12,
+    rt_sigaction = 13,
+    rt_sigprocmask = 14,
+    rt_sigreturn = 15,
+    ioctl = 16,
+    pread64 = 17,
+    pwrite64 = 18,
+    readv = 19,
+    writev = 20,
+    access = 21,
+    pipe = 22,
+    select = 23,
+    sched_yield = 24,
+    mremap = 25,
+    msync = 26,
+    mincore = 27,
+    madvise = 28,
+    shmget = 29,
+    shmat = 30,
+    shmctl = 31,
+    dup = 32,
+    dup2 = 33,
+    pause = 34,
+    nanosleep = 35,
+    getitimer = 36,
+    alarm = 37,
+    setitimer = 38,
+    getpid = 39,
+    sendfile = 40,
+    socket = 41,
+    connect = 42,
+    accept = 43,
+    sendto = 44,
+    recvfrom = 45,
+    sendmsg = 46,
+    recvmsg = 47,
+    shutdown = 48,
+    bind = 49,
+    listen = 50,
+    getsockname = 51,
+    getpeername = 52,
+    socketpair = 53,
+    setsockopt = 54,
+    getsockopt = 55,
+    clone = 56,
+    fork = 57,
+    vfork = 58,
+    execve = 59,
+    exit = 60,
+    wait4 = 61,
+    kill = 62,
+    uname = 63,
+    semget = 64,
+    semop = 65,
+    semctl = 66,
+    shmdt = 67,
+    msgget = 68,
+    msgsnd = 69,
+    msgrcv = 70,
+    msgctl = 71,
+    fcntl = 72,
+    flock = 73,
+    fsync = 74,
+    fdatasync = 75,
+    truncate = 76,
+    ftruncate = 77,
+    getdents = 78,
+    getcwd = 79,
+    chdir = 80,
+    fchdir = 81,
+    rename = 82,
+    mkdir = 83,
+    rmdir = 84,
+    creat = 85,
+    link = 86,
+    unlink = 87,
+    symlink = 88,
+    readlink = 89,
+    chmod = 90,
+    fchmod = 91,
+    chown = 92,
+    fchown = 93,
+    lchown = 94,
+    umask = 95,
+    gettimeofday = 96,
+    getrlimit = 97,
+    getrusage = 98,
+    sysinfo = 99,
+    times = 100,
+    ptrace = 101,
+    getuid = 102,
+    syslog = 103,
+    getgid = 104,
+    setuid = 105,
+    setgid = 106,
+    geteuid = 107,
+    getegid = 108,
+    setpgid = 109,
+    getppid = 110,
+    getpgrp = 111,
+    setsid = 112,
+    setreuid = 113,
+    setregid = 114,
+    getgroups = 115,
+    setgroups = 116,
+    setresuid = 117,
+    getresuid = 118,
+    setresgid = 119,
+    getresgid = 120,
+    getpgid = 121,
+    setfsuid = 122,
+    setfsgid = 123,
+    getsid = 124,
+    capget = 125,
+    capset = 126,
+    rt_sigpending = 127,
+    rt_sigtimedwait = 128,
+    rt_sigqueueinfo = 129,
+    rt_sigsuspend = 130,
+    sigaltstack = 131,
+    utime = 132,
+    mknod = 133,
+    uselib = 134,
+    personality = 135,
+    ustat = 136,
+    statfs = 137,
+    fstatfs = 138,
+    sysfs = 139,
+    getpriority = 140,
+    setpriority = 141,
+    sched_setparam = 142,
+    sched_getparam = 143,
+    sched_setscheduler = 144,
+    sched_getscheduler = 145,
+    sched_get_priority_max = 146,
+    sched_get_priority_min = 147,
+    sched_rr_get_interval = 148,
+    mlock = 149,
+    munlock = 150,
+    mlockall = 151,
+    munlockall = 152,
+    vhangup = 153,
+    modify_ldt = 154,
+    pivot_root = 155,
+    _sysctl = 156,
+    prctl = 157,
+    arch_prctl = 158,
+    adjtimex = 159,
+    setrlimit = 160,
+    chroot = 161,
+    sync = 162,
+    acct = 163,
+    settimeofday = 164,
+    mount = 165,
+    umount2 = 166,
+    swapon = 167,
+    swapoff = 168,
+    reboot = 169,
+    sethostname = 170,
+    setdomainname = 171,
+    iopl = 172,
+    ioperm = 173,
+    create_module = 174,
+    init_module = 175,
+    delete_module = 176,
+    get_kernel_syms = 177,
+    query_module = 178,
+    quotactl = 179,
+    nfsservctl = 180,
+    getpmsg = 181,
+    putpmsg = 182,
+    afs_syscall = 183,
+    tuxcall = 184,
+    security = 185,
+    gettid = 186,
+    readahead = 187,
+    setxattr = 188,
+    lsetxattr = 189,
+    fsetxattr = 190,
+    getxattr = 191,
+    lgetxattr = 192,
+    fgetxattr = 193,
+    listxattr = 194,
+    llistxattr = 195,
+    flistxattr = 196,
+    removexattr = 197,
+    lremovexattr = 198,
+    fremovexattr = 199,
+    tkill = 200,
+    time = 201,
+    futex = 202,
+    sched_setaffinity = 203,
+    sched_getaffinity = 204,
+    set_thread_area = 205,
+    io_setup = 206,
+    io_destroy = 207,
+    io_getevents = 208,
+    io_submit = 209,
+    io_cancel = 210,
+    get_thread_area = 211,
+    lookup_dcookie = 212,
+    epoll_create = 213,
+    epoll_ctl_old = 214,
+    epoll_wait_old = 215,
+    remap_file_pages = 216,
+    getdents64 = 217,
+    set_tid_address = 218,
+    restart_syscall = 219,
+    semtimedop = 220,
+    fadvise64 = 221,
+    timer_create = 222,
+    timer_settime = 223,
+    timer_gettime = 224,
+    timer_getoverrun = 225,
+    timer_delete = 226,
+    clock_settime = 227,
+    clock_gettime = 228,
+    clock_getres = 229,
+    clock_nanosleep = 230,
+    exit_group = 231,
+    epoll_wait = 232,
+    epoll_ctl = 233,
+    tgkill = 234,
+    utimes = 235,
+    vserver = 236,
+    mbind = 237,
+    set_mempolicy = 238,
+    get_mempolicy = 239,
+    mq_open = 240,
+    mq_unlink = 241,
+    mq_timedsend = 242,
+    mq_timedreceive = 243,
+    mq_notify = 244,
+    mq_getsetattr = 245,
+    kexec_load = 246,
+    waitid = 247,
+    add_key = 248,
+    request_key = 249,
+    keyctl = 250,
+    ioprio_set = 251,
+    ioprio_get = 252,
+    inotify_init = 253,
+    inotify_add_watch = 254,
+    inotify_rm_watch = 255,
+    migrate_pages = 256,
+    openat = 257,
+    mkdirat = 258,
+    mknodat = 259,
+    fchownat = 260,
+    futimesat = 261,
+    fstatat64 = 262,
+    unlinkat = 263,
+    renameat = 264,
+    linkat = 265,
+    symlinkat = 266,
+    readlinkat = 267,
+    fchmodat = 268,
+    faccessat = 269,
+    pselect6 = 270,
+    ppoll = 271,
+    unshare = 272,
+    set_robust_list = 273,
+    get_robust_list = 274,
+    splice = 275,
+    tee = 276,
+    sync_file_range = 277,
+    vmsplice = 278,
+    move_pages = 279,
+    utimensat = 280,
+    epoll_pwait = 281,
+    signalfd = 282,
+    timerfd_create = 283,
+    eventfd = 284,
+    fallocate = 285,
+    timerfd_settime = 286,
+    timerfd_gettime = 287,
+    accept4 = 288,
+    signalfd4 = 289,
+    eventfd2 = 290,
+    epoll_create1 = 291,
+    dup3 = 292,
+    pipe2 = 293,
+    inotify_init1 = 294,
+    preadv = 295,
+    pwritev = 296,
+    rt_tgsigqueueinfo = 297,
+    perf_event_open = 298,
+    recvmmsg = 299,
+    fanotify_init = 300,
+    fanotify_mark = 301,
+    prlimit64 = 302,
+    name_to_handle_at = 303,
+    open_by_handle_at = 304,
+    clock_adjtime = 305,
+    syncfs = 306,
+    sendmmsg = 307,
+    setns = 308,
+    getcpu = 309,
+    process_vm_readv = 310,
+    process_vm_writev = 311,
+    kcmp = 312,
+    finit_module = 313,
+    sched_setattr = 314,
+    sched_getattr = 315,
+    renameat2 = 316,
+    seccomp = 317,
+    getrandom = 318,
+    memfd_create = 319,
+    kexec_file_load = 320,
+    bpf = 321,
+    execveat = 322,
+    userfaultfd = 323,
+    membarrier = 324,
+    mlock2 = 325,
+    copy_file_range = 326,
+    preadv2 = 327,
+    pwritev2 = 328,
+    pkey_mprotect = 329,
+    pkey_alloc = 330,
+    pkey_free = 331,
+    statx = 332,
+    io_pgetevents = 333,
+    rseq = 334,
+    pidfd_send_signal = 424,
+    io_uring_setup = 425,
+    io_uring_enter = 426,
+    io_uring_register = 427,
+    open_tree = 428,
+    move_mount = 429,
+    fsopen = 430,
+    fsconfig = 431,
+    fsmount = 432,
+    fspick = 433,
+    pidfd_open = 434,
+    clone3 = 435,
+    close_range = 436,
+    openat2 = 437,
+    pidfd_getfd = 438,
+    faccessat2 = 439,
+    process_madvise = 440,
+    epoll_pwait2 = 441,
+    mount_setattr = 442,
+    quotactl_fd = 443,
+    landlock_create_ruleset = 444,
+    landlock_add_rule = 445,
+    landlock_restrict_self = 446,
+    memfd_secret = 447,
+    process_mrelease = 448,
+    futex_waitv = 449,
+    set_mempolicy_home_node = 450,
+    cachestat = 451,
+};
+
 const FileDescriptor = s32;
 
 const ProtectionFlags = struct(u32) {
@@ -38,17 +411,22 @@ const get_map_flags = fn(flags: std.os.MapFlags) MapFlags{
 }
 
 const mmap = fn(address: ?[&]u8, length: usize, protection_flags: ProtectionFlags, map_flags: MapFlags, fd: s32, offset: u64) usize {
-    const result = #syscall(9, #cast(address), length, #cast(protection_flags), #cast(map_flags), fd, offset);
+    const result = #syscall(#cast(Syscall.mmap), #cast(address), length, #cast(protection_flags), #cast(map_flags), fd, offset);
     return result;
 }
 
 const munmap = fn(bytes_ptr: [&]const u8, bytes_len: usize) usize {
-    const result = #syscall(11, #cast(bytes_ptr), bytes_len);
+    const result = #syscall(#cast(Syscall.munmap), #cast(bytes_ptr), bytes_len);
     return result;
 }
 
 const readlink = fn(file_path: [&:0]const u8, bytes_ptr: [&]u8, bytes_len: usize) usize {
-    const result = #syscall(89, #cast(file_path), #cast(bytes_ptr), bytes_len);
+    const result = #syscall(#cast(Syscall.readlink), #cast(file_path), #cast(bytes_ptr), bytes_len);
+    return result;
+}
+
+const fork = fn() usize {
+    const result = #syscall(#cast(Syscall.fork));
     return result;
 }
 
diff --git a/lib/std/std.nat b/lib/std/std.nat
index f4c52d6..7ddb972 100644
--- a/lib/std/std.nat
+++ b/lib/std/std.nat
@@ -2,6 +2,7 @@ comptime {
     _ = start;
 }
 
+const build = #import("build.nat");
 const builtin = #import("builtin.nat");
 const os = #import("os.nat");
 const start = #import("start.nat");
@@ -134,4 +135,10 @@ const copy_bytes = fn(destination: []u8, source: []const u8) void {
     }
 }
 
+const Target = struct {
+    cpu: builtin.Cpu,
+    os: builtin.Os,
+    abi: builtin.Abi,
+};
+
 var page_allocator = PageAllocator{};
diff --git a/test/fork/main.nat b/test/fork/main.nat
new file mode 100644
index 0000000..8e7f968
--- /dev/null
+++ b/test/fork/main.nat
@@ -0,0 +1,15 @@
+const std = #import("std");
+const main = fn() s32 {
+    if (std.os.duplicate_process()) |pid| {
+        if (pid == 0) {
+            std.print(bytes = "Hello from child\n");
+            std.os.exit(exit_code = 0);
+        } else {
+            std.print(bytes = "Hello from parent\n");
+            return 0;
+        }
+    } else {
+        std.print(bytes = "Unable to create child process\n");
+        return 1;
+    }
+}