diff --git a/std/os/wasi.zig b/std/os/wasi.zig
index c273fc6c9e..df1b099bb3 100644
--- a/std/os/wasi.zig
+++ b/std/os/wasi.zig
@@ -1,90 +1,9 @@
 pub use @import("wasi/core.zig");
 
-// Based on https://github.com/CraneStation/wasi-sysroot/blob/wasi/libc-bottom-half/headers/public/wasi/core.h
-// and https://github.com/WebAssembly/WASI/blob/master/design/WASI-core.md
-
 pub const STDIN_FILENO = 0;
 pub const STDOUT_FILENO = 1;
 pub const STDERR_FILENO = 2;
 
-pub const ESUCCESS = 0;
-pub const E2BIG = 1;
-pub const EACCES = 2;
-pub const EADDRINUSE = 3;
-pub const EADDRNOTAVAIL = 4;
-pub const EAFNOSUPPORT = 5;
-pub const EAGAIN = 6;
-pub const EALREADY = 7;
-pub const EBADF = 8;
-pub const EBADMSG = 9;
-pub const EBUSY = 10;
-pub const ECANCELED = 11;
-pub const ECHILD = 12;
-pub const ECONNABORTED = 13;
-pub const ECONNREFUSED = 14;
-pub const ECONNRESET = 15;
-pub const EDEADLK = 16;
-pub const EDESTADDRREQ = 17;
-pub const EDOM = 18;
-pub const EDQUOT = 19;
-pub const EEXIST = 20;
-pub const EFAULT = 21;
-pub const EFBIG = 22;
-pub const EHOSTUNREACH = 23;
-pub const EIDRM = 24;
-pub const EILSEQ = 25;
-pub const EINPROGRESS = 26;
-pub const EINTR = 27;
-pub const EINVAL = 28;
-pub const EIO = 29;
-pub const EISCONN = 30;
-pub const EISDIR = 31;
-pub const ELOOP = 32;
-pub const EMFILE = 33;
-pub const EMLINK = 34;
-pub const EMSGSIZE = 35;
-pub const EMULTIHOP = 36;
-pub const ENAMETOOLONG = 37;
-pub const ENETDOWN = 38;
-pub const ENETRESET = 39;
-pub const ENETUNREACH = 40;
-pub const ENFILE = 41;
-pub const ENOBUFS = 42;
-pub const ENODEV = 43;
-pub const ENOENT = 44;
-pub const ENOEXEC = 45;
-pub const ENOLCK = 46;
-pub const ENOLINK = 47;
-pub const ENOMEM = 48;
-pub const ENOMSG = 49;
-pub const ENOPROTOOPT = 50;
-pub const ENOSPC = 51;
-pub const ENOSYS = 52;
-pub const ENOTCONN = 53;
-pub const ENOTDIR = 54;
-pub const ENOTEMPTY = 55;
-pub const ENOTRECOVERABLE = 56;
-pub const ENOTSOCK = 57;
-pub const ENOTSUP = 58;
-pub const ENOTTY = 59;
-pub const ENXIO = 60;
-pub const EOVERFLOW = 61;
-pub const EOWNERDEAD = 62;
-pub const EPERM = 63;
-pub const EPIPE = 64;
-pub const EPROTO = 65;
-pub const EPROTONOSUPPORT = 66;
-pub const EPROTOTYPE = 67;
-pub const ERANGE = 68;
-pub const EROFS = 69;
-pub const ESPIPE = 70;
-pub const ESRCH = 71;
-pub const ESTALE = 72;
-pub const ETIMEDOUT = 73;
-pub const ETXTBSY = 74;
-pub const EXDEV = 75;
-pub const ENOTCAPABLE = 76;
-
 // TODO: implement this like darwin does
 pub fn getErrno(r: usize) usize {
     const signed_r = @bitCast(isize, r);
diff --git a/std/os/wasi/core.zig b/std/os/wasi/core.zig
index 23a0c7ba65..24a19c04fa 100644
--- a/std/os/wasi/core.zig
+++ b/std/os/wasi/core.zig
@@ -1,21 +1,248 @@
-pub const clockid_t = u32;
-pub const errno_t = u16;
-pub const exitcode_t = u32;
-pub const fd_t = u32;
-pub const signal_t = u8;
-pub const timestamp_t = u64;
+// Based on https://github.com/CraneStation/wasi-sysroot/blob/wasi/libc-bottom-half/headers/public/wasi/core.h
+// and https://github.com/WebAssembly/WASI/blob/master/design/WASI-core.md
+
+pub const advice_t = u8;
+pub const ADVICE_NORMAL: advice_t = 0;
+pub const ADVICE_SEQUENTIAL: advice_t = 1;
+pub const ADVICE_RANDOM: advice_t = 2;
+pub const ADVICE_WILLNEED: advice_t = 3;
+pub const ADVICE_DONTNEED: advice_t = 4;
+pub const ADVICE_NOREUSE: advice_t = 5;
 
 pub const ciovec_t = extern struct {
     buf: [*]const u8,
     buf_len: usize,
 };
 
+pub const clockid_t = u32;
 pub const CLOCK_REALTIME: clockid_t = 0;
 pub const CLOCK_MONOTONIC: clockid_t = 1;
 pub const CLOCK_PROCESS_CPUTIME_ID: clockid_t = 2;
 pub const CLOCK_THREAD_CPUTIME_ID: clockid_t = 3;
 
+pub const device_t = u64;
+
+pub const dircookie_t = u64;
+pub const DIRCOOKIE_START: dircookie_t = 0;
+
+pub const errno_t = u16;
+pub const ESUCCESS: errno_t = 0;
+pub const E2BIG: errno_t = 1;
+pub const EACCES: errno_t = 2;
+pub const EADDRINUSE: errno_t = 3;
+pub const EADDRNOTAVAIL: errno_t = 4;
+pub const EAFNOSUPPORT: errno_t = 5;
+pub const EAGAIN: errno_t = 6;
+pub const EALREADY: errno_t = 7;
+pub const EBADF: errno_t = 8;
+pub const EBADMSG: errno_t = 9;
+pub const EBUSY: errno_t = 10;
+pub const ECANCELED: errno_t = 11;
+pub const ECHILD: errno_t = 12;
+pub const ECONNABORTED: errno_t = 13;
+pub const ECONNREFUSED: errno_t = 14;
+pub const ECONNRESET: errno_t = 15;
+pub const EDEADLK: errno_t = 16;
+pub const EDESTADDRREQ: errno_t = 17;
+pub const EDOM: errno_t = 18;
+pub const EDQUOT: errno_t = 19;
+pub const EEXIST: errno_t = 20;
+pub const EFAULT: errno_t = 21;
+pub const EFBIG: errno_t = 22;
+pub const EHOSTUNREACH: errno_t = 23;
+pub const EIDRM: errno_t = 24;
+pub const EILSEQ: errno_t = 25;
+pub const EINPROGRESS: errno_t = 26;
+pub const EINTR: errno_t = 27;
+pub const EINVAL: errno_t = 28;
+pub const EIO: errno_t = 29;
+pub const EISCONN: errno_t = 30;
+pub const EISDIR: errno_t = 31;
+pub const ELOOP: errno_t = 32;
+pub const EMFILE: errno_t = 33;
+pub const EMLINK: errno_t = 34;
+pub const EMSGSIZE: errno_t = 35;
+pub const EMULTIHOP: errno_t = 36;
+pub const ENAMETOOLONG: errno_t = 37;
+pub const ENETDOWN: errno_t = 38;
+pub const ENETRESET: errno_t = 39;
+pub const ENETUNREACH: errno_t = 40;
+pub const ENFILE: errno_t = 41;
+pub const ENOBUFS: errno_t = 42;
+pub const ENODEV: errno_t = 43;
+pub const ENOENT: errno_t = 44;
+pub const ENOEXEC: errno_t = 45;
+pub const ENOLCK: errno_t = 46;
+pub const ENOLINK: errno_t = 47;
+pub const ENOMEM: errno_t = 48;
+pub const ENOMSG: errno_t = 49;
+pub const ENOPROTOOPT: errno_t = 50;
+pub const ENOSPC: errno_t = 51;
+pub const ENOSYS: errno_t = 52;
+pub const ENOTCONN: errno_t = 53;
+pub const ENOTDIR: errno_t = 54;
+pub const ENOTEMPTY: errno_t = 55;
+pub const ENOTRECOVERABLE: errno_t = 56;
+pub const ENOTSOCK: errno_t = 57;
+pub const ENOTSUP: errno_t = 58;
+pub const ENOTTY: errno_t = 59;
+pub const ENXIO: errno_t = 60;
+pub const EOVERFLOW: errno_t = 61;
+pub const EOWNERDEAD: errno_t = 62;
+pub const EPERM: errno_t = 63;
+pub const EPIPE: errno_t = 64;
+pub const EPROTO: errno_t = 65;
+pub const EPROTONOSUPPORT: errno_t = 66;
+pub const EPROTOTYPE: errno_t = 67;
+pub const ERANGE: errno_t = 68;
+pub const EROFS: errno_t = 69;
+pub const ESPIPE: errno_t = 70;
+pub const ESRCH: errno_t = 71;
+pub const ESTALE: errno_t = 72;
+pub const ETIMEDOUT: errno_t = 73;
+pub const ETXTBSY: errno_t = 74;
+pub const EXDEV: errno_t = 75;
+pub const ENOTCAPABLE: errno_t = 76;
+
+pub const eventrwflags_t = u16;
+pub const EVENT_FD_READWRITE_HANGUP: eventrwflags_t = 0x0001;
+
+pub const eventtype_t = u8;
+pub const EVENTTYPE_CLOCK: eventtype_t = 0;
+pub const EVENTTYPE_FD_READ: eventtype_t = 1;
+pub const EVENTTYPE_FD_WRITE: eventtype_t = 2;
+
+pub const exitcode_t = u32;
+
+pub const fd_t = u32;
+
+pub const fdflags_t = u16;
+pub const FDFLAG_APPEND: fdflags_t = 0x0001;
+pub const FDFLAG_DSYNC: fdflags_t = 0x0002;
+pub const FDFLAG_NONBLOCK: fdflags_t = 0x0004;
+pub const FDFLAG_RSYNC: fdflags_t = 0x0008;
+pub const FDFLAG_SYNC: fdflags_t = 0x0010;
+
+pub const filedelta_t = i64;
+
+pub const filesize_t = u64;
+
+pub const filetype_t = u8;
+pub const FILETYPE_UNKNOWN: filetype_t = 0;
+pub const FILETYPE_BLOCK_DEVICE: filetype_t = 1;
+pub const FILETYPE_CHARACTER_DEVICE: filetype_t = 2;
+pub const FILETYPE_DIRECTORY: filetype_t = 3;
+pub const FILETYPE_REGULAR_FILE: filetype_t = 4;
+pub const FILETYPE_SOCKET_DGRAM: filetype_t = 5;
+pub const FILETYPE_SOCKET_STREAM: filetype_t = 6;
+pub const FILETYPE_SYMBOLIC_LINK: filetype_t = 7;
+
+pub const fstflags_t = u16;
+pub const FILESTAT_SET_ATIM: fstflags_t = 0x0001;
+pub const FILESTAT_SET_ATIM_NOW: fstflags_t = 0x0002;
+pub const FILESTAT_SET_MTIM: fstflags_t = 0x0004;
+pub const FILESTAT_SET_MTIM_NOW: fstflags_t = 0x0008;
+
+pub const inode_t = u64;
+
+pub const linkcount_t = u32;
+
+pub const lookupflags_t = u32;
+pub const LOOKUP_SYMLINK_FOLLOW: lookupflags_t = 0x00000001;
+
+pub const oflags_t = u16;
+pub const O_CREAT: oflags_t = 0x0001;
+pub const O_DIRECTORY: oflags_t = 0x0002;
+pub const O_EXCL: oflags_t = 0x0004;
+pub const O_TRUNC: oflags_t = 0x0008;
+
+pub const riflags_t = u16;
+pub const SOCK_RECV_PEEK: riflags_t = 0x0001;
+pub const SOCK_RECV_WAITALL: riflags_t = 0x0002;
+
+pub const rights_t = u64;
+pub const RIGHT_FD_DATASYNC: rights_t = 0x0000000000000001;
+pub const RIGHT_FD_READ: rights_t = 0x0000000000000002;
+pub const RIGHT_FD_SEEK: rights_t = 0x0000000000000004;
+pub const RIGHT_FD_FDSTAT_SET_FLAGS: rights_t = 0x0000000000000008;
+pub const RIGHT_FD_SYNC: rights_t = 0x0000000000000010;
+pub const RIGHT_FD_TELL: rights_t = 0x0000000000000020;
+pub const RIGHT_FD_WRITE: rights_t = 0x0000000000000040;
+pub const RIGHT_FD_ADVISE: rights_t = 0x0000000000000080;
+pub const RIGHT_FD_ALLOCATE: rights_t = 0x0000000000000100;
+pub const RIGHT_PATH_CREATE_DIRECTORY: rights_t = 0x0000000000000200;
+pub const RIGHT_PATH_CREATE_FILE: rights_t = 0x0000000000000400;
+pub const RIGHT_PATH_LINK_SOURCE: rights_t = 0x0000000000000800;
+pub const RIGHT_PATH_LINK_TARGET: rights_t = 0x0000000000001000;
+pub const RIGHT_PATH_OPEN: rights_t = 0x0000000000002000;
+pub const RIGHT_FD_READDIR: rights_t = 0x0000000000004000;
+pub const RIGHT_PATH_READLINK: rights_t = 0x0000000000008000;
+pub const RIGHT_PATH_RENAME_SOURCE: rights_t = 0x0000000000010000;
+pub const RIGHT_PATH_RENAME_TARGET: rights_t = 0x0000000000020000;
+pub const RIGHT_PATH_FILESTAT_GET: rights_t = 0x0000000000040000;
+pub const RIGHT_PATH_FILESTAT_SET_SIZE: rights_t = 0x0000000000080000;
+pub const RIGHT_PATH_FILESTAT_SET_TIMES: rights_t = 0x0000000000100000;
+pub const RIGHT_FD_FILESTAT_GET: rights_t = 0x0000000000200000;
+pub const RIGHT_FD_FILESTAT_SET_SIZE: rights_t = 0x0000000000400000;
+pub const RIGHT_FD_FILESTAT_SET_TIMES: rights_t = 0x0000000000800000;
+pub const RIGHT_PATH_SYMLINK: rights_t = 0x0000000001000000;
+pub const RIGHT_PATH_REMOVE_DIRECTORY: rights_t = 0x0000000002000000;
+pub const RIGHT_PATH_UNLINK_FILE: rights_t = 0x0000000004000000;
+pub const RIGHT_POLL_FD_READWRITE: rights_t = 0x0000000008000000;
+pub const RIGHT_SOCK_SHUTDOWN: rights_t = 0x0000000010000000;
+
+pub const roflags_t = u16;
+pub const SOCK_RECV_DATA_TRUNCATED: roflags_t = 0x0001;
+
+pub const sdflags_t = u8;
+pub const SHUT_RD: sdflags_t = 0x01;
+pub const SHUT_WR: sdflags_t = 0x02;
+
+pub const siflags_t = u16;
+
+pub const signal_t = u8;
+pub const SIGHUP: signal_t = 1;
+pub const SIGINT: signal_t = 2;
+pub const SIGQUIT: signal_t = 3;
+pub const SIGILL: signal_t = 4;
+pub const SIGTRAP: signal_t = 5;
 pub const SIGABRT: signal_t = 6;
+pub const SIGBUS: signal_t = 7;
+pub const SIGFPE: signal_t = 8;
+pub const SIGKILL: signal_t = 9;
+pub const SIGUSR1: signal_t = 10;
+pub const SIGSEGV: signal_t = 11;
+pub const SIGUSR2: signal_t = 12;
+pub const SIGPIPE: signal_t = 13;
+pub const SIGALRM: signal_t = 14;
+pub const SIGTERM: signal_t = 15;
+pub const SIGCHLD: signal_t = 16;
+pub const SIGCONT: signal_t = 17;
+pub const SIGSTOP: signal_t = 18;
+pub const SIGTSTP: signal_t = 19;
+pub const SIGTTIN: signal_t = 20;
+pub const SIGTTOU: signal_t = 21;
+pub const SIGURG: signal_t = 22;
+pub const SIGXCPU: signal_t = 23;
+pub const SIGXFSZ: signal_t = 24;
+pub const SIGVTALRM: signal_t = 25;
+pub const SIGPROF: signal_t = 26;
+pub const SIGWINCH: signal_t = 27;
+pub const SIGPOLL: signal_t = 28;
+pub const SIGPWR: signal_t = 29;
+pub const SIGSYS: signal_t = 30;
+
+pub const subclockflags_t = u16;
+pub const SUBSCRIPTION_CLOCK_ABSTIME: subclockflags_t = 0x0001;
+
+pub const timestamp_t = u64;
+
+pub const userdata_t = u64;
+
+pub const whence_t = u8;
+pub const WHENCE_CUR: whence_t = 0;
+pub const WHENCE_END: whence_t = 1;
+pub const WHENCE_SET: whence_t = 2;
 
 pub extern "wasi_unstable" fn args_get(argv: [*][*]u8, argv_buf: [*]u8) errno_t;
 pub extern "wasi_unstable" fn args_sizes_get(argc: *usize, argv_buf_size: *usize) errno_t;