// time — clocks, instants, durations. Mirrors Hare's lib/time
// (ref/hare/time/duration.ha, instant.ha, arithm.ha,
// +linux/functions.ha). Calendar / date / strftime / timezone /
// sleep live in separate Hare modules and graduate when callers /
// supporting stdlib arrive.
//
// `duration` is a NAMED alias of i64 (lib/math/random precedent
// at lib/math/random/random.ww:8); ww treats NAMED as a newtype,
// so cross-i64 arithmetic inside this module needs explicit casts.
// Hare's structural alias semantics let those casts vanish, but
// our type checker is strict.

package time;

@symbol("rt_syscall") fn syscall2(num: i64, a: i64, b: i64) i64;
@symbol("rt_abort")   fn abort(msg: str) void;

def SYS_CLOCK_GETTIME: i64 = 228;

// ref/hare/time/duration.ha:6. 290y representable range.
export type duration = i64;

// ref/hare/time/duration.ha:9-18. Plan-9 naming (lowercase)
// diverges from Hare's uppercase per project rule 4.
export def nanosecond:  duration = 1i64;
export def microsecond: duration = 1000i64;
export def millisecond: duration = 1000000i64;
export def second:      duration = 1000000000i64;

// ref/hare/time/instant.ha:9. (sec, nsec) pair — NOT POSIX struct
// timespec (which uses u32 nsec). Layout matches Linux's struct
// timespec on 64-bit (i64+i64) so we can pass &instant directly
// to clock_gettime.
export type instant = struct {
	sec:  i64,
	nsec: i64,
};

// ref/hare/time/+linux/functions.ha:84. First cut exposes only
// realtime and monotonic; Hare's process_cpu / thread_cpu / boot /
// realtime_alarm / boot_alarm / tai graduate when a caller needs
// them (CLAUDE.md rule 9 — Hare-fidelity, no premature surface).
export type clock = enum i32 {
	realtime  = 0,
	monotonic = 1,
};

// ref/hare/time/+linux/functions.ha:138. Hare's now() also aborts
// on impossible errnos. (instant | oserror) is deliberately not
// the return shape — EINVAL / EFAULT are programmer errors (bad
// clock id, bad ptr), and a 1-word-payload sum return walks into
// task #9's cgen-divergence trap.
export fn now(c: clock) instant = {
	let i: instant;
	let rc = syscall2(SYS_CLOCK_GETTIME, (c as i32): i64, (&i): i64);
	if (rc != 0i64) { abort("time.now: clock_gettime failed"); };
	return i;
};

// ref/hare/time/arithm.ha:9. Adds duration to instant. The
// negative-duration branch normalises nsec into [0, second).
export fn add(i: instant, x: duration) instant = {
	let r: instant;
	let xi: i64 = x: i64;
	let sec: i64 = second: i64;
	let nsec: i64 = nanosecond: i64;
	if (xi == 0i64) {
		r.sec  = i.sec;
		r.nsec = i.nsec;
		return r;
	};
	if (xi > 0i64) {
		r.sec  = i.sec + (i.nsec + xi) / sec;
		r.nsec = (i.nsec + xi) % sec;
		return r;
	};
	r.sec  = i.sec + (i.nsec + xi - sec + nsec) / sec;
	r.nsec = (i.nsec + (xi % sec) + sec) % sec;
	return r;
};

// ref/hare/time/arithm.ha:26. Returns duration from a to b.
// Sign convention: b - a.
export fn diff(a: instant, b: instant) duration = {
	let sec: i64 = second: i64;
	let v: i64 = ((b.sec - a.sec) * sec) + (b.nsec - a.nsec);
	return v: duration;
};

// ref/hare/time/arithm.ha:32. -1 if a < b, 0 if equal, +1 if a > b.
export fn compare(a: instant, b: instant) i8 = {
	if (a.sec  < b.sec)  { return -1i8; };
	if (a.sec  > b.sec)  { return  1i8; };
	if (a.nsec < b.nsec) { return -1i8; };
	if (a.nsec > b.nsec) { return  1i8; };
	return 0i8;
};

// os — process and filesystem facade. The body of each call lands
// either in libwwrt.a (rt_syscall trampoline) or libc bindings,
// depending on how the program was linked.

package os;

import time;

@symbol("rt_syscall") fn syscall0(num: nr) i64;
@symbol("rt_syscall") fn syscall1(num: nr, a: i64) i64;
@symbol("rt_syscall") fn syscall2(num: nr, a: i64, b: i64) i64;
@symbol("rt_syscall") fn syscall3(num: nr, a: i64, b: i64, c: i64) i64;
@symbol("rt_syscall") fn syscall4(num: nr, a: i64, b: i64, c: i64, d: i64) i64;

@symbol("rt_free")  export fn free(p: *void, n: u64) void;
@symbol("rt_abort") fn abort(msg: str) void;

// Hare-style runtime check. Caller passes a message that's printed
// to stderr before exit(1).
export fn assert(cond: bool, msg: str) void = {
	if (!cond) { abort(msg); };
};

// Linux amd64 syscall numbers. Internal to this module — passed as
// the first arg of syscall0..4 via libwwrt's rt_syscall trampoline.
// `nr` is the type so the call sites can't accidentally pass an
// arbitrary i64 (`syscall1(0i64, ...)` no longer typechecks).
type nr = enum i64 {
	READ        = 0,
	WRITE       = 1,
	OPEN        = 2,
	CLOSE       = 3,
	LSEEK       = 8,
	ACCESS      = 21,
	DUP2        = 33,
	GETPID      = 39,
	FORK        = 57,
	EXECVE      = 59,
	EXIT        = 60,
	WAIT4       = 61,
	MKDIR       = 83,
	RMDIR       = 84,
	UNLINK      = 87,
	GETCWD      = 79,
	GETDENTS64  = 217,
	NEWFSTATAT  = 262,
};

// open(2) flags. Linux values, matching <fcntl.h>. Hare names them
// `fs::flag::RDONLY` etc; we use the same leaf names so callers say
// `os.flag.RDONLY` and `os.flag.WRONLY | os.flag.CREATE`.
export type flag = enum i32 {
	RDONLY  = 0,
	WRONLY  = 1,
	RDWR    = 2,
	CREATE  = 64,	// 0x40
	EXCL    = 128,	// 0x80 — pair with CREATE to fail on existing path
	TRUNC   = 512,	// 0x200
};

// lseek(2) whence. Hare names it `io::whence`.
export type whence = enum i32 {
	SET = 0,
	CUR = 1,
	END = 2,
};

export fn exit(code: i32) void = {
	syscall1(nr.EXIT, code: i64);
};

// PATH_MAX / pathbuf / kpath — port of Hare's ref/hare/sys/+linux/
// syscalls.ha:25,27,29-55. Hare's `path` accepts a sum `(str |
// []u8 | *const u8)`; ww's lib/os public surface narrows to `str`
// (the Hare-faithful surface at ref/hare/os/os.ha:37,47,50 etc).
// Internally, [[kpath]] copies the `str` bytes into a single
// module-level [[pathbuf]] scratch slot and NUL-terminates so the
// raw Linux syscalls (which require C strings) see a valid
// terminator. Same precedent as Hare's static `pathbuf`.
//
// Non-reentrant: one buffer, every [[stat]] / [[open]] / etc.
// rewrites it. Same caveat as strconv's `*tos` family (overwritten
// on next call). Caller must NOT hold a kpath-returned pointer
// across another lib/os path call. Graduates when ww grows a
// thread story.
//
// `nil`-as-overflow over `(*u8 | oserror)`: wwstage over-allocates
// 1-word-payload tagged returns to 24B (cstage emits 16B).
// Task #9; revert at task #10 when fixed. Repro at
// .ai/probe_tagged_return_pointer_payload.ww.
export def PATH_MAX: i32 = 4096;
let pathbuf: [4096]u8;

fn kpath(p: str) *u8 = {
	if (p.len + 1 >= PATH_MAX) { return nil: *u8; };	// ENAMETOOLONG
	let i: i32 = 0;
	for (i < p.len) { pathbuf[i] = p[i]; i += 1; };
	pathbuf[p.len] = 0u8;
	return &pathbuf[0];
};

// Raw, non-fallible primitives. These return Linux's int conventions
// (negative = -errno, non-negative = bytes/fd/etc). Callers wanting a
// Hare-style fallible API use the wrappers below.
export fn write(fd: i32, buf: *u8, n: u64) i64 = {
	return syscall3(nr.WRITE, fd: i64, buf: i64, n: i64);
};

export fn read(fd: i32, buf: *u8, n: u64) i64 = {
	return syscall3(nr.READ, fd: i64, buf: i64, n: i64);
};

export fn close(fd: i32) i32 = {
	return syscall1(nr.CLOSE, fd: i64): i32;
};

// dup2(2): make `newfd` refer to the same description as `oldfd`,
// closing `newfd` first if open. Returns `newfd` on success or a
// negative errno. Used by w6c_ww to redirect stdout into an output
// file without changing the cgen emit path.
export fn dup2(oldfd: i32, newfd: i32) i32 = {
	return syscall2(nr.DUP2, oldfd: i64, newfd: i64): i32;
};

// Fallible wrappers. The error variant is `oserror` (an i64 carrying
// -errno). The sum type makes success/failure explicit and lets
// callers `?` the result up the stack.
export fn tryread(fd: i32, buf: *u8, n: u64) (i64 | oserror) = {
	let r: i64 = read(fd, buf, n);
	if (r < 0) { return r: oserror; };
	return r;
};

export fn trywrite(fd: i32, buf: *u8, n: u64) (i64 | oserror) = {
	let r: i64 = write(fd, buf, n);
	if (r < 0) { return r: oserror; };
	return r;
};

// open — Linux open(2). Returns -errno on failure, fd otherwise.
// Higher-level callers prefer `tryopen`. Mirrors Hare's os::open
// (ref/hare/os/os.ha:117); kpath lands the bytes in pathbuf.
// Returns -ENAMETOOLONG (-36) if the path overflows PATH_MAX.
export fn open(path: str, flags: flag, mode: i32) i32 = {
	let p: *u8 = kpath(path);
	if (p == nil: *u8) { return -36i32; };	// ENAMETOOLONG
	return syscall3(nr.OPEN, p: i64, (flags as i32): i64, mode: i64): i32;
};

export fn tryopen(path: str, flags: flag, mode: i32) (i32 | oserror) = {
	let fd: i32 = open(path, flags, mode);
	if (fd < 0) { return fd: i64: oserror; };
	return fd;
};

// lseek — set/inspect the fd's position. Returns the new offset or
// a negative errno. We use this for fstat-free file-size discovery
// (open ⇒ lseek to end ⇒ lseek back).
export fn lseek(fd: i32, off: i64, w: whence) i64 = {
	return syscall3(nr.LSEEK, fd: i64, off, (w as i32): i64);
};

// oserror — the underlying errno from a failed syscall, as a
// negative i64 (Linux's int convention; e.g. -2 = ENOENT). The
// `!`-flagged alias makes ?-propagation pick this variant as the
// error half of any (T | oserror) shape. Hare's analogue is
// errors::errno carried inside io::error.
export type oserror = !i64;

// filesize — byte length of an open fd via lseek-to-end-and-back.
export fn filesize(fd: i32) (i64 | oserror) = {
	let end: i64 = lseek(fd, 0i64, whence.END);
	if (end < 0) { return end: oserror; };
	let r: i64 = lseek(fd, 0i64, whence.SET);
	if (r < 0) { return r: oserror; };
	return end;
};

// readall — keep reading until `n` bytes have arrived or the fd
// closes early. Hare name (io::readall); the buffer is caller-
// supplied, matching the Plan 9 subset convention.
export fn readall(fd: i32, buf: *u8, n: u64) (i64 | oserror) = {
	let got: u64 = 0u64;
	for (got < n) {
		let r: i64 = read(fd, buf + got, n - got);
		if (r < 0) { return r: oserror; };
		if (r == 0) { return got: i64; };	// short read: caller decides
		got += r: u64;
	};
	return got: i64;
};

// writeall — keep writing until `n` bytes have been accepted or the
// fd refuses progress. Hare name (io::writeall).
export fn writeall(fd: i32, buf: *u8, n: u64) (i64 | oserror) = {
	let sent: u64 = 0u64;
	for (sent < n) {
		let r: i64 = write(fd, buf + sent, n - sent);
		if (r < 0) { return r: oserror; };
		if (r == 0) { return sent: i64; };
		sent += r: u64;
	};
	return sent: i64;
};

// ---- process and filesystem helpers used by the `ww` driver ----------

// access(2): returns 0 if the file is reachable, negative errno
// otherwise. mode is the bitset described in <unistd.h> (F_OK=0).
// Mirrors Hare's os::access (ref/hare/os/+linux/fs.ha:access).
// Returns -ENAMETOOLONG (-36) if the path overflows PATH_MAX.
export fn access(path: str, mode: i32) i32 = {
	let p: *u8 = kpath(path);
	if (p == nil: *u8) { return -36i32; };
	return syscall2(nr.ACCESS, p: i64, mode: i64): i32;
};

// remove — unlink(2). Mirrors Hare's os::remove
// (ref/hare/os/os.ha:12).
export fn remove(path: str) i32 = {
	let p: *u8 = kpath(path);
	if (p == nil: *u8) { return -36i32; };
	return syscall1(nr.UNLINK, p: i64): i32;
};

// mkdir — mkdir(2). Mode is the unix permission bitset (e.g. 0o700).
// Returns 0 on success, negative errno otherwise. Mirrors Hare's
// os::mkdir (ref/hare/os/os.ha:50).
export fn mkdir(path: str, mode: i32) i32 = {
	let p: *u8 = kpath(path);
	if (p == nil: *u8) { return -36i32; };
	return syscall2(nr.MKDIR, p: i64, mode: i64): i32;
};

// rmdir — rmdir(2). Mirrors Hare's os::rmdir
// (ref/hare/os/os.ha:58).
export fn rmdir(path: str) i32 = {
	let p: *u8 = kpath(path);
	if (p == nil: *u8) { return -36i32; };
	return syscall1(nr.RMDIR, p: i64): i32;
};

// mkdirs — recursive mkdir. Creates `path` and any non-existent
// parent directories with the given mode. EEXIST is silently
// accepted (matches Hare's `errors::exists` skip in os::mkdirs);
// any other syscall failure surfaces as `oserror`.
//
// Mirrors Hare's os::mkdirs (ref/hare/os/os.ha:54). The in-place
// '/' → NUL splice walks the kpath-loaded [[pathbuf]] directly
// instead of recursing through [[mkdir]] — re-entering kpath would
// clobber the buffer mid-walk (single static slot, see kpath's
// non-reentrancy note above).
export fn mkdirs(path: str, mode: i32) (void | oserror) = {
	let cp: *u8 = kpath(path);
	if (cp == nil: *u8) { return -36i64: oserror; };
	let n: i32 = path.len;
	if (n == 0) { return; };

	// Walk forward; at each '/' boundary, NUL-terminate the prefix,
	// raw MKDIR syscall on pathbuf, restore the slash, continue.
	// Skip index 0 so a leading '/' on absolute paths doesn't
	// trigger an empty mkdir.
	let i: i32 = 1;
	for (i < n) {
		if (pathbuf[i] == 47u8) {	// '/'
			pathbuf[i] = 0u8;
			let r: i32 = syscall2(nr.MKDIR,
			    (&pathbuf[0]): i64, mode: i64): i32;
			pathbuf[i] = 47u8;
			if (r < 0) {
				if (r != -17) { return r: i64: oserror; };
			};
		};
		i += 1;
	};

	let r: i32 = syscall2(nr.MKDIR,
	    (&pathbuf[0]): i64, mode: i64): i32;
	if (r < 0) {
		if (r != -17) { return r: i64: oserror; };
	};
	return;
};

// getpid(2). Used by the driver to mint unique scratch paths.
export fn getpid() i32 = {
	return syscall0(nr.GETPID): i32;
};

// fork(2): 0 in the child, child pid in the parent, negative errno
// on failure.
export fn fork() i32 = {
	return syscall0(nr.FORK): i32;
};

// execve(2): on success, does not return. Mirrors Hare's
// os::exec::exec path arg (str). argv/envp stay `**u8` — the
// kernel takes a NUL-pointer-terminated table of NUL-terminated
// C strings, a different shape from a path.
export fn execve(path: str, argv: **u8, envp: **u8) i32 = {
	let p: *u8 = kpath(path);
	if (p == nil: *u8) { return -36i32; };
	return syscall3(nr.EXECVE, p: i64, argv: i64, envp: i64): i32;
};

// wait4(2): wait for `pid` (or any child if -1), store status in
// `*status`, return the pid that ended (or negative errno).
export fn wait4(pid: i32, status: *i32, options: i32, rusage: *void) i32 = {
	return syscall4(nr.WAIT4, pid: i64, status: i64,
	    options: i64, rusage: i64): i32;
};

// getcwd(2) — Linux flavour. Writes the NUL-terminated cwd into `buf`
// and returns the number of bytes written (including the NUL), or a
// negative errno. The driver uses it to expand `.` to the cwd's
// basename for `ww build` / `ww test`.
export fn getcwd(buf: *u8, n: u64) i64 = {
	return syscall2(nr.GETCWD, buf: i64, n: i64);
};

// getdents64(2) — Linux directory enumeration. The fd must be opened
// with O_RDONLY on a directory. `buf` receives a packed sequence of
// linux_dirent64 records:
//
//   struct linux_dirent64 {
//       u64  d_ino;       // 0..7
//       i64  d_off;       // 8..15
//       u16  d_reclen;    // 16..17  — total bytes for this record
//       u8   d_type;      // 18      — DT_REG/DT_DIR/...
//       u8   d_name[];    // 19..    — NUL-terminated name + padding
//   };
//
// Returns bytes written into `buf` (advance by d_reclen to walk),
// 0 at end-of-directory, or a negative errno.
export fn getdents64(fd: i32, buf: *u8, n: u64) i64 = {
	return syscall3(nr.GETDENTS64, fd: i64, buf: i64, n: i64);
};

// ---- environment ------------------------------------------------------

// rt_envp — runtime-side getter. rt/start.s captures envp into a DATAW
// slot before calling main; this binding lifts the captured pointer
// into ww. Same FFI shape as rt_syscall / rt_malloc / rt_abort: a TEXT
// symbol the linker resolves. The returned `**u8` is a NUL-terminated
// table of `*u8` entries, each pointing at a NUL-terminated
// "NAME=VALUE" byte sequence.
//
// We don't expose `rtenvp` directly; [[getenv]] is the only consumer.
@symbol("rt_envp") fn rtenvp() **u8;

// getenv — POSIX getenv. Returns a borrowed `str` view over the value
// bytes of the named environment variable, or void if the name is not
// present. The view is valid for the process lifetime — the bytes
// live in the kernel-supplied envp table at process entry. A future
// `setenv` (separate task) that grows the table behind the scenes
// would invalidate prior views; v1 has no setenv, so callers can
// hold the view indefinitely.
//
// Mirrors Hare's os::tryenv shape (returns void rather than panicking
// on missing). Hare also ships os::getenv (`(str | void)`) and
// os::mustenv (panic-on-missing); ww collapses to the single
// `(str | void)` form for now — consumers wanting "must" semantics
// abort at the call site.
//
// Algorithm: walk the NUL-pointer-terminated `environ` table doing a
// "name=" prefix match against each entry, byte-wise. NUL inside
// `name` would never match a real env var (env var names cannot
// contain '\0'), so we don't filter — POSIX puts that responsibility
// on the caller.
export fn getenv(name: str) (str | void) = {
	let envp: **u8 = rtenvp();
	let i: i32 = 0;
	for (true) {
		let entry: *u8 = envp[i];
		if (entry == nil: *u8) { return; };
		let j: i32 = 0;
		let matched: bool = true;
		for (j < name.len) {
			if (entry[j] == 0u8) { matched = false; break; };
			if (entry[j] != name[j]) { matched = false; break; };
			j += 1;
		};
		if (matched) {
			if (entry[name.len] == 61u8) {	// '='
				let val: *u8 = entry + ((name.len + 1): u64);
				let n: i32 = 0;
				for (val[n] != 0u8) { n += 1; };
				let r: str;
				r.ptr = val;
				r.len = n;
				return r;
			};
		};
		i += 1;
	};
	return;
};

// ---- stat / lstat / fstat / exists -----------------------------------
//
// Ports of Hare's stat family (ref/hare/fs/fs.ha:172,196 +
// ref/hare/sys/+linux/stat.ha:24-58). The Hare surface returns
// `filestat` by value; ww's cgreturn ABI tops out at 24B today (see
// STATUS task #21) and filestat is 80B, so [[stat]] / [[lstat]] /
// [[fstat]] take an out-parameter and return `(void | oserror)`.
// Re-evaluate the by-value shape when full sret lands.
//
// `filestat`, `mode`, and `stat_mask` live in lib/os because ww has
// no lib/fs yet; Hare puts them in `fs::`. These types graduate to
// lib/fs when that module ships — callers should expect a future
// re-export.
//
// Underlying syscall is SYS_newfstatat (262), which unifies
// stat/lstat/fstat through the `dirfd + flags` triple:
//   stat  = newfstatat(AT_FDCWD, path,  0)
//   lstat = newfstatat(AT_FDCWD, path,  AT_SYMLINK_NOFOLLOW)
//   fstat = newfstatat(fd,       "",    AT_EMPTY_PATH)
// Avoiding SYS_statx — its 256B variable layout would buy btime,
// but Hare's filestat doesn't expose btime either, so we stay on
// the simpler 144B kernel struct.

// fstatat(2) flag values. Linux constants from <linux/fcntl.h>.
// Names mirror Hare's ref/hare/sys/+linux/types.ha:45-51 (capital-
// AT_ prefix, top-level `def`s).
export def AT_FDCWD:            i32 = -100;
export def AT_SYMLINK_NOFOLLOW: i32 = 256;	// 0x100
export def AT_EMPTY_PATH:       i32 = 4096;	// 0x1000

// mode — file-mode bits. Mirrors Hare's fs::mode (ref/hare/fs/
// types.ha:63). Permission bits are the standard Unix octal subset;
// type bits live in the S_IFMT = 0o170000 region. Type-bit test:
//
//   let t: u32 = (fi.mode as u32) & 61440u32;	// 0o170000 mask
//   if (t == os.mode.DIR as u32) { /* directory */ };
//
// Numeric values are octal in Hare's source; ww has no octal
// literals so they're written as decimal with the octal in a
// trailing comment.
export type mode = enum u32 {
	// permission bits
	USER_RWX  = 448u32,	// 0o700
	USER_RW   = 384u32,	// 0o600
	USER_RX   = 320u32,	// 0o500
	USER_R    = 256u32,	// 0o400
	USER_W    = 128u32,	// 0o200
	USER_X    = 64u32,	// 0o100
	GROUP_RWX = 56u32,	// 0o070
	GROUP_RW  = 48u32,	// 0o060
	GROUP_RX  = 40u32,	// 0o050
	GROUP_R   = 32u32,	// 0o040
	GROUP_W   = 16u32,	// 0o020
	GROUP_X   = 8u32,	// 0o010
	OTHER_RWX = 7u32,	// 0o007
	OTHER_RW  = 6u32,	// 0o006
	OTHER_RX  = 5u32,	// 0o005
	OTHER_R   = 4u32,	// 0o004
	OTHER_W   = 2u32,	// 0o002
	OTHER_X   = 1u32,	// 0o001
	SETUID    = 2048u32,	// 0o4000
	SETGID    = 1024u32,	// 0o2000
	STICKY    = 512u32,	// 0o1000
	// file-type bits (S_IFMT mask = 0o170000 = 61440)
	UNKNOWN   = 0u32,
	FIFO      = 4096u32,	// 0o010000
	CHR       = 8192u32,	// 0o020000
	DIR       = 16384u32,	// 0o040000
	BLK       = 24576u32,	// 0o060000
	REG       = 32768u32,	// 0o100000
	LINK      = 40960u32,	// 0o120000
	SOCK      = 49152u32,	// 0o140000
};

// stat_mask — which filestat fields the call populated. Mirrors
// Hare's fs::stat_mask (ref/hare/fs/types.ha:129). newfstatat fills
// every field, so [[stat]] / [[lstat]] / [[fstat]] always set all
// seven bits OR-folded (see [[fillfilestat]]); per-bit testing is
// the documented sparse-backend pattern (cf. Hare's fs::fs network
// backends that only populate mtime+size).
export type stat_mask = enum u32 {
	UID   = 1u32,
	GID   = 2u32,
	SIZE  = 4u32,
	INODE = 8u32,
	ATIME = 16u32,
	MTIME = 32u32,
	CTIME = 64u32,
};

// filestat — Hare's fs::filestat (ref/hare/fs/types.ha:141). 80
// bytes. Times are time.instant (ref/hare/time/instant.ha:9) — the
// canonical Hare shape. See module-header note re: graduation to
// lib/fs.
export type filestat = struct {
	mask:  stat_mask,	// 0  (4)
	mode:  mode,		// 4  (4)
	uid:   u32,		// 8  (4)
	gid:   u32,		// 12 (4)
	sz:    u64,		// 16 (8)
	inode: u64,		// 24 (8)
	atime: time.instant,	// 32 (16)
	mtime: time.instant,	// 48 (16)
	ctime: time.instant,	// 64 (16) — ends at 80
};

// kstat — x86_64 kernel `struct stat` layout. Mirrors
// arch/x86/include/uapi/asm/stat.h (`__kernel_ulong_t`-keyed
// fields). 144 bytes. Module-internal; SYS_newfstatat writes into
// this buffer and the public stat fns then copy the bits into the
// Hare-shaped [[filestat]].
type kstat = struct {
	dev:        u64,	// 0
	ino:        u64,	// 8
	nlink:      u64,	// 16
	mode:       u32,	// 24
	uid:        u32,	// 28
	gid:        u32,	// 32
	pad0:       u32,	// 36
	rdev:       u64,	// 40
	sz:         i64,	// 48
	blksize:    i64,	// 56
	blocks:     i64,	// 64
	atime_sec:  i64,	// 72
	atime_nsec: i64,	// 80
	mtime_sec:  i64,	// 88
	mtime_nsec: i64,	// 96
	ctime_sec:  i64,	// 104
	ctime_nsec: i64,	// 112
	unused0:    i64,	// 120
	unused1:    i64,	// 128
	unused2:    i64,	// 136 — ends at 144
};

// emptypath — single-NUL byte used as the `pathname` arg to
// newfstatat with AT_EMPTY_PATH. The kernel requires a non-NULL
// pointer to a zero-length C string, NOT a null pointer. Bytes are
// read-only from the kernel's view; ww has no module-level const so
// this is a writable `let`.
let emptypath: [1]u8 = [0u8];

// fillfilestat — copy a 144B kstat into the 80B Hare-shaped
// filestat. Internal helper used by all three public entry points.
// Mirrors Hare's st_to_filestat (ref/hare/os/+linux/dirfdfs.ha:259):
// newfstatat populates every field, so the mask is the OR-fold of
// all seven Hare stat_mask bits.
fn fillfilestat(out: *filestat, k: *kstat) void = {
	out.mask        = stat_mask.UID | stat_mask.GID | stat_mask.SIZE
	    | stat_mask.INODE | stat_mask.ATIME | stat_mask.MTIME
	    | stat_mask.CTIME;
	out.mode        = k.mode: mode;
	out.uid         = k.uid;
	out.gid         = k.gid;
	out.sz          = k.sz: u64;
	out.inode       = k.ino;
	out.atime.sec   = k.atime_sec;
	out.atime.nsec  = k.atime_nsec;
	out.mtime.sec   = k.mtime_sec;
	out.mtime.nsec  = k.mtime_nsec;
	out.ctime.sec   = k.ctime_sec;
	out.ctime.nsec  = k.ctime_nsec;
};

// stat — fill *out with metadata for `path`. Follows symlinks.
// Returns ENAMETOOLONG (-36) as `oserror` if the path overflows
// PATH_MAX.
//
// Mirrors Hare's sys::stat (ref/hare/sys/+linux/stat.ha:51) modulo
// the out-param shape forced by the cgreturn 24B cap. Note: Hare's
// higher-level fs::stat (ref/hare/fs/fs.ha:172) instead has lstat
// semantics — we follow sys::stat's POSIX-stat behavior here.
export fn stat(out: *filestat, path: str) (void | oserror) = {
	let cp: *u8 = kpath(path);
	if (cp == nil: *u8) { return -36i64: oserror; };
	let k: kstat;
	let r: i64 = syscall4(nr.NEWFSTATAT,
	    AT_FDCWD: i64, cp: i64, (&k): i64, 0i64);
	if (r < 0) { return r: oserror; };
	fillfilestat(out, &k);
};

// lstat — like [[stat]] but does NOT follow a terminal symlink.
// Mirrors Hare's sys::lstat (ref/hare/sys/+linux/stat.ha:57).
export fn lstat(out: *filestat, path: str) (void | oserror) = {
	let cp: *u8 = kpath(path);
	if (cp == nil: *u8) { return -36i64: oserror; };
	let k: kstat;
	let r: i64 = syscall4(nr.NEWFSTATAT,
	    AT_FDCWD: i64, cp: i64, (&k): i64,
	    AT_SYMLINK_NOFOLLOW: i64);
	if (r < 0) { return r: oserror; };
	fillfilestat(out, &k);
};

// fstat — like [[stat]] but addresses the file by fd. Uses
// newfstatat(fd, "", AT_EMPTY_PATH); the kernel resolves the fd
// directly. Mirrors Hare's sys::fstat (ref/hare/sys/+linux/stat.ha:54).
export fn fstat(out: *filestat, fd: i32) (void | oserror) = {
	let k: kstat;
	let r: i64 = syscall4(nr.NEWFSTATAT,
	    fd: i64, (&emptypath[0]): i64, (&k): i64,
	    AT_EMPTY_PATH: i64);
	if (r < 0) { return r: oserror; };
	fillfilestat(out, &k);
};

// exists — true if `path` resolves to anything (regular file,
// directory, symlink, ...). Stat-shaped (Hare's `fs::exists`,
// ref/hare/fs/fs.ha:196) — no separate syscall. Symlinks are
// followed; a dangling symlink is `false`. ENAMETOOLONG is
// swallowed as `false` — Hare's os::exists doc says "true if a
// node exists at the given path, or false if not."
//
// Race warning: prefer "open and handle the error" over "exists
// then open" in real code (Hare's docstring carries the same
// note). The race is unavoidable in this shape.
//
// Goes through SYS_newfstatat directly rather than match'ing on
// [[stat]]'s `(void | oserror)` return. Functionally identical;
// the direct shape sidesteps a cstage/wwstage cgen disagreement
// on the slot size of `(void | oserror)` (cstage 16B, wwstage 24B
// — same class as STATUS #22, surfaced first time a match on this
// shape combined with an 80B local-struct local frame). Use the
// match shape once #22 lands.
export fn exists(path: str) bool = {
	let cp: *u8 = kpath(path);
	if (cp == nil: *u8) { return false; };
	let k: kstat;
	let r: i64 = syscall4(nr.NEWFSTATAT,
	    AT_FDCWD: i64, cp: i64, (&k): i64, 0i64);
	return r >= 0i64;
};

// rt — runtime primitives exposed to ww programs.
// Mirrors Hare's rt:: module placement (ref/hare/rt/).

package rt;

// malloc — mmap-backed page allocator. Untyped: `malloc(n)` returns a
// `*void`; callers cast to the target type. Diverges from Hare: Hare
// exposes `alloc` / `free` as typed language builtins that the
// compiler lowers to rt::malloc/rt::free; ww has no such builtins,
// so the rt-symbol surface is exposed directly. Stdlib callers that
// need a typed allocation pattern wrap this with a cast plus a stored
// capacity (see [[strings.dup]], [[memio.dynamic]]).
//
// OOM: rt_malloc is a bare mmap(MAP_ANON|MAP_PRIVATE) wrapper with no
// error path. The raw Linux mmap syscall returns a negative errno cast
// to `*void` on failure (e.g. `(void*)-12` for ENOMEM); the
// `MAP_FAILED` (`(void*)-1`) value is a libc-wrapper convention that
// rt_malloc doesn't apply. Neither `== nil` nor `== (void*)-1` catches
// it; any deref of such a return faults. Today the stdlib does not
// check; OOM faults on first dereference. A typed fallible variant is
// a future task (task #39). ref/hare/rt/malloc.ha:27.
@symbol("rt_malloc") export fn malloc(n: u64) *void;

// selfhost/cmd/wcc/mem.ww — port of cmd/wcc/mem.c.
//
// Bump arena allocator. Backed by the runtime page allocator
// (rt_malloc / rt_free), no libc. Each chunk is mmap'd; when the
// current chunk runs out we link a fresh one. Freeing the arena
// unmaps the chain.
//
// Memory handed out is 16-byte aligned. The C version under
// cmd/wcc/ is retained until the three-stage bootstrap diffs clean.

package wcc;

import os;
import rt;

def ALIGN: u64       = 16u64;
def INIT_CHUNK: u64  = 65536u64;
def MAX_CHUNK: u64   = 4194304u64;
def ARENA_SZ: u64    = 48u64;	// sizeof(arena), kept in sync below

type arena = struct {
	buf:   *u8,
	off:   u64,
	cap:   u64,
	next:  *arena,
	total: u64,
};

fn roundup(n: u64, a: u64) u64 = {
	return (n + a - 1u64) & ~(a - 1u64);
};

export fn newarena() *arena = {
	let a: *arena = rt.malloc(ARENA_SZ): *arena;
	a.buf = rt.malloc(INIT_CHUNK): *u8;
	a.off = 0u64;
	a.cap = INIT_CHUNK;
	a.next = nil;
	a.total = 0u64;
	return a;
};

// Grow: link a fresh chunk in front of the head. We push the old
// chunk into `next` so the head always describes the current bump
// region. Chunk size doubles up to MAX_CHUNK.
fn grow(a: *arena, need: u64) bool = {
	let want: u64 = a.cap * 2u64;
	if (want < need) { want = need; };
	if (want > MAX_CHUNK) { want = MAX_CHUNK; };
	if (want < need) { return false; };	// single allocation too big

	let old: *arena = rt.malloc(ARENA_SZ): *arena;
	old.buf = a.buf;
	old.off = a.off;
	old.cap = a.cap;
	old.next = a.next;
	old.total = 0u64;

	a.buf = rt.malloc(want): *u8;
	a.off = 0u64;
	a.cap = want;
	a.next = old;
	return true;
};

export fn amalloc(a: *arena, n: u64) *void = {
	let need: u64 = roundup(n, ALIGN);
	if (need > a.cap - a.off) {
		if (!grow(a, need)) { return nil; };
	};
	let p: *u8 = a.buf + a.off;
	a.off += need;
	a.total += need;
	// Zero the region. Plan 9 amalloc zeroes; we mirror that here so
	// the checker can assume freshly allocated nodes start at 0.
	let i: u64 = 0u64;
	for (i < need) {
		p[i] = 0u8;
		i += 1u64;
	};
	return p: *void;
};

// astrndup — copy `n` bytes into the arena and produce a NUL-terminated
// view. Returns a `str` whose ptr is arena-owned and whose len is `n`
// (the trailing NUL is past `len`, so callers reading exactly n bytes
// see no padding). Used by the lexer to capture token text.
export fn astrndup(a: *arena, src: *u8, n: u64) str = {
	let p: *u8 = amalloc(a, n + 1u64): *u8;
	let i: u64 = 0u64;
	for (i < n) {
		p[i] = src[i];
		i += 1u64;
	};
	p[n] = 0u8;
	let r: str;
	r.ptr = p;
	r.len = n: i32;
	return r;
};

export fn freearena(a: *arena) void = {
	for (a != nil) {
		let next: *arena = a.next;
		os.free(a.buf: *void, a.cap);
		os.free(a: *void, ARENA_SZ);
		a = next;
	};
};

// selfhost/cmd/w6l/sym.ww — port of cmd/w6l/sym.c.
//
// Linker symbol table. Singly-linked list, usually a few hundred
// entries; hashing isn't worth it yet.

package w6l;

import mem;

type lsym = struct {
	name:        str,
	val:         u64,	// offset within combined .text (or .data when
				// indata=1) once linked
	defined:     i32,	// 1 if some lobj defines this symbol
	indata:      i32,	// 1 if defined in .data (writable globals)
	owner:       *lobj,
	idxinowner:  i32,
	// Dynamic-linking fields. Set by resolve when an undefined sym
	// is provided by some loaded lso. pltidx and dynsymidx default
	// to -1 (set explicitly by resolve; alloc-zeroing gives 0, not -1).
	isdyn:       i32,
	dynlib:      *lso,
	dynversion:  str,	// matched export's version; len 0 if none
	pltidx:      i32,
	dynsymidx:   i32,
	snext:       *lsym,
};

type lrel = struct {
	off:    u64,	// offset within the relocation's section
	section: i32,	// 0 = .text, 1 = .data
	kind:   i32,	// R_X86_64_*
	sym:    *lsym,
	addend: i64,
	rnext:  *lrel,
};

type lobj = struct {
	path:     str,
	buf:      *u8,	// object bytes
	len:      u64,
	textoff:  u64,	// offset of .text in combined output
	textsize: u64,
	dataoff:  u64,	// offset of .data in combined output
	datasize: u64,	// bytes contributed to combined .data (0 if none)
	onext:    *lobj,
};

// lexport — one entry per GLOBAL/WEAK symbol exported by a loaded .so.
// Stored as a chain in the order the .so's dynsym presents them, so
// soprovides_v's first-match semantics agree with the C version.
type lexport = struct {
	name:    str,
	version: str,	// len 0 for unversioned globals
	enext:   *lexport,
};

type lso = struct {
	path:    str,	// full filesystem path used to load
	soname:  str,	// DT_SONAME, or basename if missing
	exports: *lexport,	// dynsym-order chain of exported names
	sonext:  *lso,
};

type lnk = struct {
	a:       *arena,
	objs:    *lobj,
	sos:     *lso,
	syms:    *lsym,
	rels:    *lrel,
	text:    *u8,	// combined .text
	textcap: u64,
	textlen: u64,
	// Combined .data (writable). Empty unless any input .o has a
	// .data PROGBITS section.
	data:    *u8,
	datacap: u64,
	datalen: u64,
	errs:    i32,
	dynn:    i32,	// number of syms routed through PLT
};

fn streq(a: str, b: str) bool = {
	if (a.len != b.len) { return false; };
	let i: i32 = 0;
	for (i < a.len) {
		if (a[i] != b[i]) { return false; };
		i += 1;
	};
	return true;
};

export fn intern(l: *lnk, name: str) *lsym = {
	let s: *lsym = l.syms;
	for (s != nil) {
		if (streq(s.name, name)) { return s; };
		s = s.snext;
	};
	let n: *lsym = alloc(lsym { name = name, snext = l.syms })!;
	l.syms = n;
	return n;
};

export fn lookup(l: *lnk, name: str) *lsym = {
	let s: *lsym = l.syms;
	for (s != nil) {
		if (streq(s.name, name)) { return s; };
		s = s.snext;
	};
	return nil;
};

// selfhost/cmd/w6l/obj.ww — port of cmd/w6l/obj.c.
//
// Loads relocatable ELF64 .o files emitted by w6a, appends .text to
// the combined image, and pulls in symbols + relocations with
// offsets adjusted to the combined section.
//
// Also handles SysV `ar` archives (libwwrt.a). The two-pass loader
// indexes members on the first pass and iteratively pulls members
// that define currently-undefined symbols on subsequent passes.

package w6l;

import os;
import rt;
import mem;
import sym;

def ET_REL:        i32 = 1;
def EM_X86_64:     i32 = 62;
def SHT_PROGBITS:  i32 = 1;
def SHT_SYMTAB:    i32 = 2;
def SHT_STRTAB:    i32 = 3;
def SHT_RELA:      i32 = 4;

// ---- little-endian byte readers ----------------------------------------
// w6a/w6l use straight LE on amd64. Reading via byte offsets keeps us off
// the cgen's u16 field-load story for now (MOVZBQ exists; MOVZWQ doesn't).

fn rdu16(p: *u8, off: u64) u16 = {
	let b0: u16 = p[off]: u16;
	let b1: u16 = p[off + 1u64]: u16;
	return b0 | (b1 << 8u16);
};

fn rdu32(p: *u8, off: u64) u32 = {
	let b0: u32 = p[off]: u32;
	let b1: u32 = p[off + 1u64]: u32;
	let b2: u32 = p[off + 2u64]: u32;
	let b3: u32 = p[off + 3u64]: u32;
	return b0 | (b1 << 8u32) | (b2 << 16u32) | (b3 << 24u32);
};

fn rdu64(p: *u8, off: u64) u64 = {
	let lo: u64 = rdu32(p, off): u64;
	let hi: u64 = rdu32(p, off + 4u64): u64;
	return lo | (hi << 32u64);
};

// ---- ELF64 section header offsets (40 bytes total) --------------------
def SHDR_SIZE:     u64 = 64u64;	// sizeof(Shdr) per ELF64 spec
def SHDR_NAME:     u64 = 0u64;
def SHDR_TYPE:     u64 = 4u64;
def SHDR_OFFSET:   u64 = 24u64;
def SHDR_SIZE_F:   u64 = 32u64;
def SHDR_LINK:     u64 = 40u64;

// ELF64 ehdr field offsets
def EHDR_SIZE:     u64 = 64u64;
def EHDR_TYPE:     u64 = 16u64;
def EHDR_MACHINE:  u64 = 18u64;
def EHDR_SHOFF:    u64 = 40u64;
def EHDR_SHENTSIZE: u64 = 58u64;
def EHDR_SHNUM:    u64 = 60u64;
def EHDR_SHSTRNDX: u64 = 62u64;

// ELF64 sym entry: 24 bytes
def SYM_SIZE:      u64 = 24u64;
def SYM_NAME:      u64 = 0u64;
def SYM_INFO:      u64 = 4u64;
def SYM_SHNDX:     u64 = 6u64;
def SYM_VALUE:     u64 = 8u64;

// ELF64 RELA entry: 24 bytes
def RELA_SIZE:     u64 = 24u64;
def RELA_OFFSET:   u64 = 0u64;
def RELA_INFO:     u64 = 8u64;
def RELA_ADDEND:   u64 = 16u64;

// ---- file slurp --------------------------------------------------------

fn slurp(path: *u8) (*u8, u64) = {
	let fd: i32 = os.open(pathstr(path), os.flag.RDONLY, 0i32);
	if (fd < 0) { return nil, 0u64; };
	let szr: (i64 | os.oserror) = os.filesize(fd);
	let n: i64 = 0i64;
	match (szr) {
	case let v: i64 => n = v;
	case let e: os.oserror => { os.close(fd); return nil, 0u64; };
	};
	let buf: *u8 = rt.malloc(n: u64): *u8;
	let rr: (i64 | os.oserror) = os.readall(fd, buf, n: u64);
	os.close(fd);
	let got: i64 = 0i64;
	match (rr) {
	case let v: i64 => got = v;
	case let e: os.oserror => return nil, 0u64;
	};
	if (got != n) { return nil, 0u64; };
	return buf, n: u64;
};

// ---- text buffer growth ------------------------------------------------

fn emittext(l: *lnk, src: *u8, n: u64) void = {
	if (l.textlen + n > l.textcap) {
		let nc: u64 = l.textcap;
		if (nc == 0u64) { nc = 4096u64; };
		for (nc < l.textlen + n) { nc = nc * 2u64; };
		// Grow by mmap'ing a fresh region and copying. The old buffer
		// is leaked into the page allocator; for a linker run this is
		// trivial waste.
		let nb: *u8 = rt.malloc(nc): *u8;
		let i: u64 = 0u64;
		for (i < l.textlen) {
			nb[i] = l.text[i];
			i += 1u64;
		};
		l.text = nb;
		l.textcap = nc;
	};
	let i: u64 = 0u64;
	for (i < n) {
		l.text[l.textlen + i] = src[i];
		i += 1u64;
	};
	l.textlen += n;
};

fn emitdata(l: *lnk, src: *u8, n: u64) void = {
	if (l.datalen + n > l.datacap) {
		let nc: u64 = l.datacap;
		if (nc == 0u64) { nc = 256u64; };
		for (nc < l.datalen + n) { nc = nc * 2u64; };
		let nb: *u8 = rt.malloc(nc): *u8;
		let i: u64 = 0u64;
		for (i < l.datalen) {
			nb[i] = l.data[i];
			i += 1u64;
		};
		l.data = nb;
		l.datacap = nc;
	};
	let i: u64 = 0u64;
	for (i < n) {
		l.data[l.datalen + i] = src[i];
		i += 1u64;
	};
	l.datalen += n;
};

// ---- C-string helpers --------------------------------------------------

fn cstrlen(p: *u8) u64 = {
	let n: u64 = 0u64;
	for (p[n] != 0u8) { n += 1u64; };
	return n;
};

// pathstr — view a NUL-terminated *u8 as a str. Bridges argv/arena
// callers to lib/os entrypoints (str post-task-#23). Shared with
// main.ww and dyn.ww via the w6l bundle.
fn pathstr(p: *u8) str = {
	let r: str;
	r.ptr = p;
	r.len = cstrlen(p): i32;
	return r;
};

fn cstreq(p: *u8, lit: str) bool = {
	let n: u64 = lit.len: u64;
	let i: u64 = 0u64;
	for (i < n) {
		let li: i32 = i: i32;
		if (p[i] != lit[li]) { return false; };
		i += 1u64;
	};
	if (p[i] != 0u8) { return false; };
	return true;
};

// Build a ww str from a NUL-terminated *u8 (for passing to intern).
fn cstrtostr(a: *arena, p: *u8) str = {
	let n: u64 = cstrlen(p);
	return astrndup(a, p, n);
};

// ---- archive (SysV ar) types and helpers -------------------------------
//
// Each archive member starts with a 60-byte ar_hdr. The fields we care
// about are the first byte (member type) and the size at offset 48 (a
// 10-byte, space-padded decimal). Member bodies are 2-byte aligned.

type defent = struct {
	name:  str,
	dnext: *defent,
};

type armember = struct {
	data:   *u8,		// arena copy of the member's ELF bytes
	size:   u64,
	defs:   *defent,	// linked list of defined globals
	loaded: i32,
	mnext:  *armember,
};

fn isarchive(p: *u8, len: u64) bool = {
	if (len < 8u64) { return false; };
	if (p[0u64] != 33u8)  { return false; };	// '!'
	if (p[1u64] != 60u8)  { return false; };	// '<'
	if (p[2u64] != 97u8)  { return false; };	// 'a'
	if (p[3u64] != 114u8) { return false; };	// 'r'
	if (p[4u64] != 99u8)  { return false; };	// 'c'
	if (p[5u64] != 104u8) { return false; };	// 'h'
	if (p[6u64] != 62u8)  { return false; };	// '>'
	if (p[7u64] != 10u8)  { return false; };	// '\n'
	return true;
};

// arfield — parse a space-padded decimal integer of width n.
fn arfield(p: *u8, n: u64) u64 = {
	let v: u64 = 0u64;
	let i: u64 = 0u64;
	for (i < n) {
		let c: u8 = p[i];
		if (c < 48u8) { return v; };	// space, NUL, etc.
		if (c > 57u8) { return v; };
		v = v * 10u64 + ((c - 48u8): u64);
		i += 1u64;
	};
	return v;
};

// elfglobals — return a linked list of names of globally-defined
// (STB_GLOBAL) symbols whose section is `.text`. Names are arena
// copies, so the source ELF buffer can be freed afterward.
fn elfglobals(a: *arena, buf: *u8, len: u64) *defent = {
	if (len < EHDR_SIZE) { return nil; };
	if (buf[0u64] != 127u8) { return nil; };
	if (buf[1u64] != 69u8)  { return nil; };
	if (buf[2u64] != 76u8)  { return nil; };
	if (buf[3u64] != 70u8)  { return nil; };

	let shoff:    u64 = rdu64(buf, EHDR_SHOFF);
	let shnum:    u32 = rdu16(buf, EHDR_SHNUM): u32;
	let shstrndx: u32 = rdu16(buf, EHDR_SHSTRNDX): u32;

	let shstrshoff: u64 = rdu64(buf, shoff + (shstrndx: u64) * SHDR_SIZE + SHDR_OFFSET);
	let shstr: *u8 = buf + shstrshoff;

	let idxtext:   i32 = -1;
	let idxdata:   i32 = -1;
	let idxsymtab: i32 = -1;
	let i: u32 = 0u32;
	for (i < shnum) {
		let secoff: u64 = shoff + (i: u64) * SHDR_SIZE;
		let shtype: u32 = rdu32(buf, secoff + SHDR_TYPE);
		let shname: u32 = rdu32(buf, secoff + SHDR_NAME);
		let nm: *u8 = shstr + (shname: u64);
		if (shtype == SHT_PROGBITS: u32) {
			if (cstreq(nm, ".text")) { idxtext = i: i32; };
			if (cstreq(nm, ".data")) { idxdata = i: i32; };
		};
		if (shtype == SHT_SYMTAB: u32)  { idxsymtab = i: i32; };
		i += 1u32;
	};
	if (idxtext < 0) { return nil; };
	if (idxsymtab < 0) { return nil; };

	let symsh:   u64 = shoff + (idxsymtab: u64) * SHDR_SIZE;
	let symoff:  u64 = rdu64(buf, symsh + SHDR_OFFSET);
	let symsize: u64 = rdu64(buf, symsh + SHDR_SIZE_F);
	let symlink: u32 = rdu32(buf, symsh + SHDR_LINK);
	let nsyms:    u64 = symsize / SYM_SIZE;

	let strsh:  u64 = shoff + (symlink: u64) * SHDR_SIZE;
	let stroff: u64 = rdu64(buf, strsh + SHDR_OFFSET);
	let strtab:  *u8 = buf + stroff;

	let head: *defent = nil;
	let si: u64 = 1u64;
	for (si < nsyms) {
		let symp: u64 = symoff + si * SYM_SIZE;
		let stname:  u32 = rdu32(buf, symp + SYM_NAME);
		let stinfo:  u8  = buf[symp + SYM_INFO];
		let stshndx: u16 = rdu16(buf, symp + SYM_SHNDX);
		let bind:     u32 = (stinfo: u32) >> 4u32;
		// STB_GLOBAL = 1; defined in .text or .data. Both are
		// included so an archive member that owns a data global
		// gets pulled in when something references it.
		if (bind == 1u32) {
			if (stshndx != 0u16) {
				let intext: bool = (stshndx: i32) == idxtext;
				let indt:   bool = false;
				if (idxdata >= 0) {
					indt = (stshndx: i32) == idxdata;
				};
				if (intext || indt) {
					let nmp: *u8 = strtab + (stname: u64);
					if (nmp[0u64] != 0u8) {
						let nm: str = cstrtostr(a, nmp);
						let de: *defent = alloc(defent { name = nm, dnext = head })!;
						head = de;
					};
				};
			};
		};
		si += 1u64;
	};
	return head;
};

// memberdefinesundef — true if any of m's defined globals matches a
// currently-undefined symbol in the linker's symbol table. Names not
// already interned are uninteresting (the link doesn't need them yet).
fn memberdefinesundef(l: *lnk, m: *armember) bool = {
	let de: *defent = m.defs;
	for (de != nil) {
		let s: *lsym = lookup(l, de.name);
		if (s != nil) {
			if (s.defined == 0) { return true; };
		};
		de = de.dnext;
	};
	return false;
};

// loadarchive — port of cmd/w6l/obj.c:load_archive.
//
// Pass 1 indexes every regular member. Pass 2 iteratively pulls in any
// member that supplies a currently-undefined symbol; each pull may
// introduce fresh undefs, so we loop until quiescent.
fn loadarchive(l: *lnk, path: *u8, buf: *u8, len: u64) i32 = {
	let head: *armember = nil;
	let tail: *armember = nil;
	let pos:  u64 = 8u64;	// past "!<arch>\n"
	for (pos + 60u64 <= len) {
		let hdrsize: u64 = arfield(buf + pos + 48u64, 10u64);
		let hdrend:  u64 = pos + 60u64;
		if (hdrend + hdrsize > len) { break; };
		let first: u8 = buf[pos];
		// Skip the symbol table ('/'), long-name table ('//'), and
		// any padding entries (NUL or space leading byte).
		if (first != 47u8) { if (first != 0u8) { if (first != 32u8) {
			let m: *armember = alloc(armember { size = hdrsize })!;
			let mb: *u8 = amalloc(l.a, hdrsize): *u8;
			let i: u64 = 0u64;
			for (i < hdrsize) {
				mb[i] = buf[hdrend + i];
				i += 1u64;
			};
			m.data = mb;
			m.defs = elfglobals(l.a, mb, hdrsize);
			if (head == nil) { head = m; }
			else { tail.mnext = m; };
			tail = m;
		}; }; };
		pos = hdrend + hdrsize;
		if ((hdrsize & 1u64) != 0u64) { pos = pos + 1u64; };
	};

	let changed: i32 = 1;
	for (changed != 0) {
		changed = 0;
		let m: *armember = head;
		for (m != nil) {
			if (m.loaded == 0) {
				if (memberdefinesundef(l, m)) {
					if (loadimage(l, path, m.data, m.size) == 0) {
						m.loaded = 1;
						changed = 1;
					};
				};
			};
			m = m.mnext;
		};
	};
	return 0;
};

// ---- main loader -------------------------------------------------------

export fn load(l: *lnk, path: *u8) i32 = {
	let bufp: *u8;
	let buflen: u64;
	bufp, buflen = slurp(path);
	if (bufp == nil) {
		os.write(2, "w6l: cannot read object\n".ptr, 23u64);
		return -1;
	};
	if (isarchive(bufp, buflen)) {
		return loadarchive(l, path, bufp, buflen);
	};
	return loadimage(l, path, bufp, buflen);
};

fn loadimage(l: *lnk, path: *u8, buf: *u8, len: u64) i32 = {
	if (len < EHDR_SIZE) { return -1; };
	// magic: 0x7f, 'E', 'L', 'F'
	if (buf[0u64] != 127u8) { return -1; };
	if (buf[1u64] != 69u8)  { return -1; };
	if (buf[2u64] != 76u8)  { return -1; };
	if (buf[3u64] != 70u8)  { return -1; };
	if (buf[4u64] != 2u8)   { return -1; };	// ELFCLASS64
	if (rdu16(buf, EHDR_TYPE)    != ET_REL: u16)    { return -1; };
	if (rdu16(buf, EHDR_MACHINE) != EM_X86_64: u16) { return -1; };

	let shoff:    u64 = rdu64(buf, EHDR_SHOFF);
	let shnum:    u32 = rdu16(buf, EHDR_SHNUM): u32;
	let shstrndx: u32 = rdu16(buf, EHDR_SHSTRNDX): u32;

	let shstrshoff: u64 = rdu64(buf, shoff + (shstrndx: u64) * SHDR_SIZE + SHDR_OFFSET);
	let shstr: *u8 = buf + shstrshoff;

	// find .text, .data, .symtab, .rela.text, .rela.data
	let idxtext:   i32 = -1;
	let idxdata:   i32 = -1;
	let idxsymtab: i32 = -1;
	let idxrela:   i32 = -1;
	let idxrelad:  i32 = -1;
	let i: u32 = 0u32;
	for (i < shnum) {
		let secoff: u64 = shoff + (i: u64) * SHDR_SIZE;
		let shtype: u32 = rdu32(buf, secoff + SHDR_TYPE);
		let shname: u32 = rdu32(buf, secoff + SHDR_NAME);
		let nm: *u8 = shstr + (shname: u64);
		if (shtype == SHT_PROGBITS: u32) {
			if (cstreq(nm, ".text")) { idxtext = i: i32; };
			if (cstreq(nm, ".data")) { idxdata = i: i32; };
		};
		if (shtype == SHT_SYMTAB: u32)  { idxsymtab = i: i32; };
		if (shtype == SHT_RELA: u32) {
			if (cstreq(nm, ".rela.text")) { idxrela = i: i32; };
			if (cstreq(nm, ".rela.data")) { idxrelad = i: i32; };
		};
		i += 1u32;
	};
	if (idxtext < 0) {
		os.write(2, "w6l: missing .text\n".ptr, 18u64);
		return -1;
	};
	if (idxsymtab < 0) {
		os.write(2, "w6l: missing .symtab\n".ptr, 20u64);
		return -1;
	};

	let textsh:   u64 = shoff + (idxtext: u64) * SHDR_SIZE;
	let textoff:  u64 = rdu64(buf, textsh + SHDR_OFFSET);
	let textsize: u64 = rdu64(buf, textsh + SHDR_SIZE_F);

	let symsh:   u64 = shoff + (idxsymtab: u64) * SHDR_SIZE;
	let symoff:  u64 = rdu64(buf, symsh + SHDR_OFFSET);
	let symsize: u64 = rdu64(buf, symsh + SHDR_SIZE_F);
	let symlink: u32 = rdu32(buf, symsh + SHDR_LINK);
	let nsyms:    u64 = symsize / SYM_SIZE;

	let strsh:  u64 = shoff + (symlink: u64) * SHDR_SIZE;
	let stroff: u64 = rdu64(buf, strsh + SHDR_OFFSET);
	let strtab:  *u8 = buf + stroff;

	let datasize: u64 = 0u64;
	let dataoff:   u64 = 0u64;
	if (idxdata >= 0) {
		let datash: u64 = shoff + (idxdata: u64) * SHDR_SIZE;
		dataoff  = rdu64(buf, datash + SHDR_OFFSET);
		datasize = rdu64(buf, datash + SHDR_SIZE_F);
	};

	// Track this object.
	let ob: *lobj = alloc(lobj {
		path     = cstrtostr(l.a, path),
		buf      = buf,
		len      = len,
		textoff  = l.textlen,
		textsize = textsize,
		dataoff  = l.datalen,
		datasize = datasize,
		onext    = l.objs,
	})!;
	l.objs = ob;

	// Append .text bytes to the combined image.
	emittext(l, buf + textoff, textsize);
	// Append .data bytes (if present) to the combined .data buffer.
	if (idxdata >= 0) {
		if (datasize > 0u64) {
			emitdata(l, buf + dataoff, datasize);
		};
	};

	// Walk symbols. We don't keep a per-object map[] of *lsym. Instead
	// the reloc loop re-walks symtab and re-interns by name. Simpler
	// than dancing around the cgen's u64-shift gaps.
	let si: u64 = 1u64;	// skip index 0 (always undef sentinel)
	for (si < nsyms) {
		let symp: u64 = symoff + si * SYM_SIZE;
		let stname:  u32 = rdu32(buf, symp + SYM_NAME);
		let stshndx: u16 = rdu16(buf, symp + SYM_SHNDX);
		let stvalue: u64 = rdu64(buf, symp + SYM_VALUE);
		let nmp: *u8 = strtab + (stname: u64);
		if (nmp[0u64] != 0u8) {
			let nm: str = cstrtostr(l.a, nmp);
			let gs: *lsym = intern(l, nm);
			if (stshndx != 0u16) {
				let intext: bool = (stshndx: i32) == idxtext;
				let indt:   bool = false;
				if (idxdata >= 0) {
					indt = (stshndx: i32) == idxdata;
				};
				if (intext) { if (indt) { indt = false; }; };
				if (intext) {
					if (gs.defined != 0) {
						os.write(2, "w6l: duplicate symbol\n".ptr, 21u64);
						l.errs += 1;
					} else {
						gs.defined = 1;
						gs.owner = ob;
						gs.idxinowner = si: i32;
						gs.val = ob.textoff + stvalue;
					};
				};
				if (indt) {
					if (gs.defined != 0) {
						os.write(2, "w6l: duplicate symbol\n".ptr, 21u64);
						l.errs += 1;
					} else {
						gs.defined = 1;
						gs.indata = 1;
						gs.owner = ob;
						gs.idxinowner = si: i32;
						gs.val = ob.dataoff + stvalue;
					};
				};
			};
		};
		si += 1u64;
	};

	// Per-object relocation collection.
	if (idxrela >= 0) {
		let relash:   u64 = shoff + (idxrela: u64) * SHDR_SIZE;
		let relaoff:  u64 = rdu64(buf, relash + SHDR_OFFSET);
		let relasize: u64 = rdu64(buf, relash + SHDR_SIZE_F);
		let nrel:      u64 = relasize / RELA_SIZE;
		let ri: u64 = 0u64;
		for (ri < nrel) {
			let rp: u64 = relaoff + ri * RELA_SIZE;
			let roff:    u64 = rdu64(buf, rp + RELA_OFFSET);
			let rinfo:   u64 = rdu64(buf, rp + RELA_INFO);
			let raddend: u64 = rdu64(buf, rp + RELA_ADDEND);
			let rsymidx: u32 = (rinfo >> 32u64): u32;
			let rkind:    i32 = ((rinfo & 4294967295u64): u32): i32;
			let nr: *lrel = alloc(lrel {
				off     = ob.textoff + roff,
				section = 0,
				kind    = rkind,
				addend  = raddend: i64,
				rnext   = l.rels,
			})!;
			// Look up the referenced sym by name (re-walk symtab).
			if ((rsymidx: u64) < nsyms) {
				let sp: u64 = symoff + (rsymidx: u64) * SYM_SIZE;
				let sname: u32 = rdu32(buf, sp + SYM_NAME);
				let snm: *u8 = strtab + (sname: u64);
				if (snm[0u64] != 0u8) {
					let nm: str = cstrtostr(l.a, snm);
					nr.sym = intern(l, nm);
				};
			};
			l.rels = nr;
			ri += 1u64;
		};
	};

	// Data-reloc collection. Offsets land in .data, shifted by
	// this object's data_off so they index the combined buffer.
	if (idxrelad >= 0) {
		let relash:   u64 = shoff + (idxrelad: u64) * SHDR_SIZE;
		let relaoff:  u64 = rdu64(buf, relash + SHDR_OFFSET);
		let relasize: u64 = rdu64(buf, relash + SHDR_SIZE_F);
		let nrel:      u64 = relasize / RELA_SIZE;
		let ri: u64 = 0u64;
		for (ri < nrel) {
			let rp: u64 = relaoff + ri * RELA_SIZE;
			let roff:    u64 = rdu64(buf, rp + RELA_OFFSET);
			let rinfo:   u64 = rdu64(buf, rp + RELA_INFO);
			let raddend: u64 = rdu64(buf, rp + RELA_ADDEND);
			let rsymidx: u32 = (rinfo >> 32u64): u32;
			let rkind:    i32 = ((rinfo & 4294967295u64): u32): i32;
			let nr: *lrel = alloc(lrel {
				off     = ob.dataoff + roff,
				section = 1,
				kind    = rkind,
				addend  = raddend: i64,
				rnext   = l.rels,
			})!;
			if ((rsymidx: u64) < nsyms) {
				let sp: u64 = symoff + (rsymidx: u64) * SYM_SIZE;
				let sname: u32 = rdu32(buf, sp + SYM_NAME);
				let snm: *u8 = strtab + (sname: u64);
				if (snm[0u64] != 0u8) {
					let nm: str = cstrtostr(l.a, snm);
					nr.sym = intern(l, nm);
				};
			};
			l.rels = nr;
			ri += 1u64;
		};
	};

	return 0;
};

// selfhost/cmd/w6l/dyn.ww — port of cmd/w6l/dyn.c.
//
// Load a shared object (ET_DYN) so the linker knows which symbols it
// exports and which DT_NEEDED entry to record. We do not pull bytes
// from the .so; the dynamic loader maps it at runtime.
//
// Each call appends one lso to lnk->sos. l_so_provides_v answers
// "does this .so export the named symbol, and at which version?" —
// l_resolve uses that to promote unresolved references to dynamic.

package w6l;

import os;
import rt;
import mem;
import sym;

def ET_DYN_SO:     u16 = 3u16;
def EM_X86_64_SO:  u16 = 62u16;

def SHT_DYNAMIC:        u32 = 6u32;
def SHT_DYNSYM:         u32 = 11u32;
// GNU extensions, sh_type values.
def SHT_GNU_VERDEF:     u32 = 1879048189u32;	// 0x6ffffffd
def SHT_GNU_VERNEED:    u32 = 1879048190u32;	// 0x6ffffffe
def SHT_GNU_VERSYM:     u32 = 1879048191u32;	// 0x6fffffff

def DT_NULL_TAG:        i64 = 0i64;
def DT_SONAME_TAG:      i64 = 14i64;

// Versym special values.
def VER_NDX_LOCAL_C:    u16 = 0u16;
def VER_NDX_GLOBAL_C:   u16 = 1u16;
def VERSYM_HIDDEN_C:    u16 = 32768u16;	// 0x8000
def VERSYM_VERSION_C:   u16 = 32767u16;	// 0x7fff

// ELF64 ehdr field offsets (subset)
def EH_SHOFF:      u64 = 40u64;
def EH_ETYPE:      u64 = 16u64;
def EH_EMACHINE:   u64 = 18u64;
def EH_SHENTSIZE:  u64 = 58u64;
def EH_SHNUM:      u64 = 60u64;
def EH_SHSTRNDX:   u64 = 62u64;

// ELF64 Shdr (64 bytes)
def SH_SIZE:       u64 = 64u64;
def SH_TYPE:       u64 = 4u64;
def SH_OFFSET:     u64 = 24u64;
def SH_SIZE_F:     u64 = 32u64;
def SH_LINK:       u64 = 40u64;
def SH_ENTSIZE:    u64 = 56u64;

// ELF64 Sym (24 bytes)
def SY_SIZE:       u64 = 24u64;
def SY_NAME:       u64 = 0u64;
def SY_INFO:       u64 = 4u64;
def SY_SHNDX:      u64 = 6u64;

// ELF64 Dyn (16 bytes)
def DY_SIZE:       u64 = 16u64;
def DY_TAG:        u64 = 0u64;
def DY_VAL:        u64 = 8u64;

// Verdef (20 bytes)
def VD_SIZE:       u64 = 20u64;
def VD_NDX:        u64 = 4u64;
def VD_CNT:        u64 = 6u64;
def VD_AUX:        u64 = 12u64;
def VD_NEXT:       u64 = 16u64;

// Verdaux (8 bytes)
def VA_NAME:       u64 = 0u64;
def VA_NEXT:       u64 = 4u64;

// ---- little-endian byte readers ---------------------------------------

fn du16(p: *u8, off: u64) u16 = {
	let b0: u16 = p[off]: u16;
	let b1: u16 = p[off + 1u64]: u16;
	return b0 | (b1 << 8u16);
};

fn du32(p: *u8, off: u64) u32 = {
	let b0: u32 = p[off]: u32;
	let b1: u32 = p[off + 1u64]: u32;
	let b2: u32 = p[off + 2u64]: u32;
	let b3: u32 = p[off + 3u64]: u32;
	return b0 | (b1 << 8u32) | (b2 << 16u32) | (b3 << 24u32);
};

fn du64(p: *u8, off: u64) u64 = {
	let lo: u64 = du32(p, off): u64;
	let hi: u64 = du32(p, off + 4u64): u64;
	return lo | (hi << 32u64);
};

fn di64(p: *u8, off: u64) i64 = {
	return du64(p, off): i64;
};

// ---- C-string helpers --------------------------------------------------

fn dcstrlen(p: *u8) u64 = {
	let n: u64 = 0u64;
	for (p[n] != 0u8) { n += 1u64; };
	return n;
};

fn dcstrtostr(a: *arena, p: *u8) str = {
	let n: u64 = dcstrlen(p);
	return astrndup(a, p, n);
};

// basename: scan for last '/' and return pointer past it.
fn dbasename(p: *u8) *u8 = {
	let n: u64 = dcstrlen(p);
	let i: u64 = n;
	for (i > 0u64) {
		i -= 1u64;
		if (p[i] == 47u8) {	// '/'
			return p + i + 1u64;
		};
	};
	return p;
};

// ---- file slurp --------------------------------------------------------

fn slurpso(path: *u8) (*u8, u64) = {
	let fd: i32 = os.open(pathstr(path), os.flag.RDONLY, 0i32);
	if (fd < 0) { return nil, 0u64; };
	let szr: (i64 | os.oserror) = os.filesize(fd);
	let n: i64 = 0i64;
	match (szr) {
	case let v: i64 => n = v;
	case let e: os.oserror => { os.close(fd); return nil, 0u64; };
	};
	let buf: *u8 = rt.malloc(n: u64): *u8;
	let rr: (i64 | os.oserror) = os.readall(fd, buf, n: u64);
	os.close(fd);
	let got: i64 = 0i64;
	match (rr) {
	case let v: i64 => got = v;
	case let e: os.oserror => return nil, 0u64;
	};
	if (got != n) { return nil, 0u64; };
	return buf, n: u64;
};

// ---- verdef helpers ----------------------------------------------------

// vdnameat — walk verdef records and return the name (as *u8 into
// the .so's verstr buffer) for the entry whose vd_ndx == ndx. The name
// is the first Verdaux's vda_name (subsequent auxes are predecessor
// names). Returns nil if no entry matches.
fn vdnameat(buf: *u8, verdefoff: u64, verdefsize: u64,
		verstr: *u8, ndx: u16) *u8 = {
	let off: u64 = 0u64;
	for (off < verdefsize) {
		let vdp: u64 = verdefoff + off;
		let vdndx: u16 = du16(buf, vdp + VD_NDX);
		let vdaux: u32 = du32(buf, vdp + VD_AUX);
		let vdnext: u32 = du32(buf, vdp + VD_NEXT);
		if (vdndx == ndx) {
			let auxp: u64 = vdp + (vdaux: u64);
			let vdaname: u32 = du32(buf, auxp + VA_NAME);
			return verstr + (vdaname: u64);
		};
		if (vdnext == 0u32) { return nil; };
		off += vdnext: u64;
	};
	return nil;
};

// ---- entry points ------------------------------------------------------

export fn loadso(l: *lnk, path: *u8) i32 = {
	let buf: *u8;
	let blen: u64;
	buf, blen = slurpso(path);
	if (buf == nil) {
		os.write(2, "w6l: cannot read .so\n".ptr, 20u64);
		return -1;
	};
	if (blen < 64u64) {
		os.write(2, "w6l: short ELF\n".ptr, 14u64);
		return -1;
	};
	if (buf[0u64] != 127u8) { return soerr("not ELF"); };
	if (buf[1u64] != 69u8)  { return soerr("not ELF"); };
	if (buf[2u64] != 76u8)  { return soerr("not ELF"); };
	if (buf[3u64] != 70u8)  { return soerr("not ELF"); };
	if (buf[4u64] != 2u8)   { return soerr("not ELFCLASS64"); };
	if (du16(buf, EH_EMACHINE) != EM_X86_64_SO) {
		return soerr("not amd64");
	};
	if (du16(buf, EH_ETYPE) != ET_DYN_SO) {
		return soerr("not ET_DYN");
	};

	let shoff: u64 = du64(buf, EH_SHOFF);
	let shnum: u32 = du16(buf, EH_SHNUM): u32;
	if (shoff == 0u64) { return soerr("stripped .so unsupported"); };
	if (shnum == 0u32) { return soerr("stripped .so unsupported"); };

	// Locate the four sections we care about.
	let idxdynsym:  i32 = -1;
	let idxdynamic: i32 = -1;
	let idxversym:  i32 = -1;
	let idxverdef:  i32 = -1;
	let i: u32 = 0u32;
	for (i < shnum) {
		let shp: u64 = shoff + (i: u64) * SH_SIZE;
		let shtype: u32 = du32(buf, shp + SH_TYPE);
		if (shtype == SHT_DYNSYM)       { idxdynsym = i: i32; };
		if (shtype == SHT_DYNAMIC)      { idxdynamic = i: i32; };
		if (shtype == SHT_GNU_VERSYM)   { idxversym = i: i32; };
		if (shtype == SHT_GNU_VERDEF)   { idxverdef = i: i32; };
		i += 1u32;
	};
	if (idxdynsym < 0) {
		return soerr("no .dynsym");
	};

	let dynsymsh: u64 = shoff + (idxdynsym: u64) * SH_SIZE;
	let dynsymoff: u64 = du64(buf, dynsymsh + SH_OFFSET);
	let dynsymsize: u64 = du64(buf, dynsymsh + SH_SIZE_F);
	let dynsymlink: u32 = du32(buf, dynsymsh + SH_LINK);
	let nsyms: u64 = dynsymsize / SY_SIZE;

	let dynstrsh: u64 = shoff + (dynsymlink: u64) * SH_SIZE;
	let dynstroff: u64 = du64(buf, dynstrsh + SH_OFFSET);
	let dynstr: *u8 = buf + dynstroff;

	// SONAME: .dynamic strings live in the section pointed at by its
	// sh_link (almost always .dynstr).
	let sonamecs: *u8 = nil;
	if (idxdynamic >= 0) {
		let dynsh: u64 = shoff + (idxdynamic: u64) * SH_SIZE;
		let dynoff: u64 = du64(buf, dynsh + SH_OFFSET);
		let dynsize: u64 = du64(buf, dynsh + SH_SIZE_F);
		let dynlink: u32 = du32(buf, dynsh + SH_LINK);
		let dstrsh: u64 = shoff + (dynlink: u64) * SH_SIZE;
		let dstroff: u64 = du64(buf, dstrsh + SH_OFFSET);
		let dstr: *u8 = buf + dstroff;
		let nd: u64 = dynsize / DY_SIZE;
		let di: u64 = 0u64;
		for (di < nd) {
			let dp: u64 = dynoff + di * DY_SIZE;
			let dtag: i64 = di64(buf, dp + DY_TAG);
			if (dtag == DT_NULL_TAG) {
				di = nd;	// break
			} else {
				if (dtag == DT_SONAME_TAG) {
					let dval: u64 = du64(buf, dp + DY_VAL);
					sonamecs = dstr + dval;
					di = nd;	// break
				} else {
					di += 1u64;
				};
			};
		};
	};
	if (sonamecs == nil) {
		sonamecs = dbasename(path);
	};

	// Versym is one u16 per dynsym entry.
	let versymoff: u64 = 0u64;
	let hasversym: i32 = 0;
	if (idxversym >= 0) {
		let vssh: u64 = shoff + (idxversym: u64) * SH_SIZE;
		versymoff = du64(buf, vssh + SH_OFFSET);
		hasversym = 1;
	};

	// Verdef section bounds + the .dynstr-like string section it uses.
	let verdefoff: u64 = 0u64;
	let verdefsize: u64 = 0u64;
	let verstr: *u8 = nil;
	if (idxverdef >= 0) {
		let vdsh: u64 = shoff + (idxverdef: u64) * SH_SIZE;
		verdefoff = du64(buf, vdsh + SH_OFFSET);
		verdefsize = du64(buf, vdsh + SH_SIZE_F);
		let vdlink: u32 = du32(buf, vdsh + SH_LINK);
		let vstrsh: u64 = shoff + (vdlink: u64) * SH_SIZE;
		let vstroff: u64 = du64(buf, vstrsh + SH_OFFSET);
		verstr = buf + vstroff;
	};

	// Build the lso. Exports are appended in dynsym order so
	// soprovides_v's first-match semantics match the C version.
	let so: *lso = alloc(lso { path = dcstrtostr(l.a, path), soname = dcstrtostr(l.a, sonamecs) })!;
	let tail: *lexport = nil;

	let si: u64 = 1u64;
	for (si < nsyms) {
		let sp: u64 = dynsymoff + si * SY_SIZE;
		let stshndx: u16 = du16(buf, sp + SY_SHNDX);
		if (stshndx == 0u16) { si += 1u64; } else {
			let stinfo: u8 = buf[sp + SY_INFO];
			let bind: u32 = (stinfo: u32) >> 4u32;
			if (bind != 1u32) { if (bind != 2u32) {
				// not GLOBAL/WEAK
				si += 1u64;
				continue;
			}; };
			let stname: u32 = du32(buf, sp + SY_NAME);
			let nmp: *u8 = dynstr + (stname: u64);
			if (nmp[0u64] == 0u8) {
				si += 1u64;
				continue;
			};

			// Determine version. Skip non-default (hidden) and
			// local entries.
			let vernamecs: *u8 = nil;
			let keep: i32 = 1;
			if (hasversym != 0) {
				let v: u16 = du16(buf, versymoff + si * 2u64);
				if ((v & VERSYM_HIDDEN_C) != 0u16) {
					keep = 0;	// non-default
				} else {
					let vidx: u16 = v & VERSYM_VERSION_C;
					if (vidx == VER_NDX_LOCAL_C) {
						keep = 0;	// not exported
					} else { if (vidx == VER_NDX_GLOBAL_C) {
						vernamecs = nil;
					} else { if (vidx == 1u16) {
						// glibc's BASE entry: treat as
						// unversioned. (The C version
						// notes that vidx==1 in Verdef
						// maps to the SONAME BASE.)
						vernamecs = nil;
					} else {
						if (verstr != nil) {
							let nm: *u8 = vdnameat(buf, verdefoff, verdefsize, verstr, vidx);
							vernamecs = nm;
						};
					}; }; };
				};
			};

			if (keep != 0) {
				let e: *lexport = alloc(lexport { name = dcstrtostr(l.a, nmp) })!;
				if (vernamecs != nil) {
					e.version = dcstrtostr(l.a, vernamecs);
				};
				if (tail == nil) {
					so.exports = e;
				} else {
					tail.enext = e;
				};
				tail = e;
			};
			si += 1u64;
		};
	};

	so.sonext = l.sos;
	l.sos = so;
	return 0;
};

fn soerr(msg: str) i32 = {
	os.write(2, "w6l: ".ptr, 4u64);
	os.write(2, msg.ptr, msg.len: u64);
	os.write(2, "\n".ptr, 1u64);
	return -1;
};

// soprovides — 1 if so exports name, 0 otherwise.
export fn soprovides(so: *lso, name: str) i32 = {
	if (so == nil) { return 0; };
	let e: *lexport = so.exports;
	for (e != nil) {
		if (streq(e.name, name)) { return 1; };
		e = e.enext;
	};
	return 0;
};

// soversion — the version of so's export named `name`, or an empty
// str (ptr=nil, len=0) if the export is unversioned or not present.
export fn soversion(so: *lso, name: str) str = {
	let result: str;
	result.ptr = nil;
	result.len = 0i32;
	if (so == nil) { return result; };
	let e: *lexport = so.exports;
	for (e != nil) {
		if (streq(e.name, name)) {
			result.ptr = e.version.ptr;
			result.len = e.version.len;
			return result;
		};
		e = e.enext;
	};
	return result;
};

// `streq` lives in sym.ww — same bundle, single definition.

// selfhost/cmd/w6l/pass.ww — port of cmd/w6l/pass.c.
//
// Resolution + relocation. l_resolve flags every undefined symbol
// referenced by a relocation, and promotes those provided by some
// loaded .so to "dynamic" with a freshly-assigned PLT slot.
// l_relocate walks the rel list and patches the .text bytes in place
// once the final virtual base is known. Dynamic refs are deferred:
// their site is patched later in dynout, once the PLT vaddr is known.
//
// Supported relocation kinds: PC32 (=2), PLT32 (=4); both are 32-bit
// PC-relative displacements (PLT32 == PC32 for static).

package w6l;

import os;
import sym;
import dyn;

def R_X86_64_64:    i32 = 1;
def R_X86_64_PC32:  i32 = 2;
def R_X86_64_PLT32: i32 = 4;

export fn resolve(l: *lnk) i32 = {
	// Initialise dynamic-linking sentinels. amalloc zeroes, so
	// isdyn/dynlib start clean — but pltidx and dynsymidx
	// must be -1, not 0.
	let si: *lsym = l.syms;
	for (si != nil) {
		si.pltidx = -1;
		si.dynsymidx = -1;
		si = si.snext;
	};

	// Promote each undefined sym that some lso exports to dynamic
	// and hand it a PLT slot. Iteration order over the relocation
	// list determines slot numbering and is stable across runs.
	let r: *lrel = l.rels;
	for (r != nil) {
		if (r.sym != nil) {
			if (r.sym.defined == 0) {
				if (r.sym.isdyn == 0) {
					let so: *lso = l.sos;
					for (so != nil) {
						if (soprovides(so, r.sym.name) != 0) {
							r.sym.isdyn = 1;
							r.sym.dynlib = so;
							r.sym.pltidx = l.dynn;
							l.dynn += 1;
							so = nil;	// break
						} else {
							so = so.sonext;
						};
					};
				};
			};
		};
		r = r.rnext;
	};

	// What remains undefined truly is undefined.
	let r2: *lrel = l.rels;
	for (r2 != nil) {
		if (r2.sym != nil) {
			if (r2.sym.defined == 0) {
				if (r2.sym.isdyn == 0) {
					os.write(2, "w6l: undefined reference to '".ptr, 28u64);
					let nm: str = r2.sym.name;
					os.write(2, nm.ptr, nm.len: u64);
					os.write(2, "'\n".ptr, 2u64);
					l.errs += 1;
				};
			};
		};
		r2 = r2.rnext;
	};
	return l.errs;
};

fn patchu32(p: *u8, v: u32) void = {
	p[0] = (v & 255u32): u8;
	p[1] = ((v >> 8u32) & 255u32): u8;
	p[2] = ((v >> 16u32) & 255u32): u8;
	p[3] = ((v >> 24u32) & 255u32): u8;
};

fn patchu64(p: *u8, v: u64) void = {
	let i: i32 = 0;
	for (i < 8) {
		p[i] = ((v >> (i: u64 * 8u64)) & 255u64): u8;
		i += 1;
	};
};

export fn relocate(l: *lnk, textva: u64, datava: u64) i32 = {
	let r: *lrel = l.rels;
	for (r != nil) {
		if (r.sym != nil) {
			// Dynamic refs are patched later in dynout once the
			// PLT vaddr is known.
			if (r.sym.isdyn != 0) {
				r = r.rnext;
				continue;
			};
			if (r.sym.defined != 0) {
				let symva: u64 = textva + r.sym.val;
				if (r.sym.indata != 0) { symva = datava + r.sym.val; };
				let k: i32 = r.kind;
				if (k == R_X86_64_PC32) {
					let site: u64 = textva + r.off;
					let rel: i64 = (symva: i64 - site: i64) + r.addend;
					patchu32(l.text + r.off, rel: u32);
				} else { if (k == R_X86_64_PLT32) {
					let site: u64 = textva + r.off;
					let rel: i64 = (symva: i64 - site: i64) + r.addend;
					patchu32(l.text + r.off, rel: u32);
				} else { if (k == R_X86_64_64) {
					// Absolute 64-bit. Currently used only
					// for DATAR slots in .data.
					let v: u64 = (symva: i64 + r.addend): u64;
					if (r.section == 1) {
						patchu64(l.data + r.off, v);
					} else {
						patchu64(l.text + r.off, v);
					};
				} else {
					os.write(2, "w6l: unsupported reloc kind\n".ptr, 27u64);
					l.errs += 1;
				};};};
			};
		};
		r = r.rnext;
	};
	return l.errs;
};

// selfhost/cmd/w6l/dynout.ww — port of cmd/w6l/dynout.c.
//
// Emit a dynamic-linked ELF executable. The shape is the simplest
// valid one: PT_INTERP + PT_DYNAMIC + DT_BIND_NOW so the loader
// resolves every PLT slot at startup (no lazy binding, no PLT0
// trampoline). SysV .hash, not .gnu.hash. Non-PIE, fixed base.
//
// Layout:
//   [0]            Ehdr
//   [64]           Phdrs (PT_LOAD R+X, PT_LOAD R+W, PT_INTERP, PT_DYNAMIC)
//   [interp_off]   "/lib64/ld-linux-x86-64.so.2\0"
//   [dynstr_off]   .dynstr
//   [dynsym_off]   .dynsym
//   [hash_off]     .hash
//   [versym_off]   .gnu.version
//   [verneed_off]  .gnu.version_r
//   [relaplt_off]  .rela.plt
//   [pad to 0x1000]
//   [text_off]     .text
//   [plt_off]      .plt
//   [pad to next page]
//   [gotplt_off]   .got.plt   (writable; mapped by PT_LOAD #2)
//   [dynamic_off]  .dynamic   (writable; covered by PT_DYNAMIC)

package w6l;

import os;
import rt;
import mem;
import sym;

// ELF constants
def ET_EXEC_D:     u16 = 2u16;
def EM_X86_64_D:   u16 = 62u16;
def EV_CURRENT_D:  u32 = 1u32;
def ELFCLASS64_D:  u8  = 2u8;
def ELFDATA2LSB_D: u8  = 1u8;

def PT_LOAD_D:     u32 = 1u32;
def PT_DYNAMIC_D:  u32 = 2u32;
def PT_INTERP_D:   u32 = 3u32;
def PF_X_D:        u32 = 1u32;
def PF_W_D:        u32 = 2u32;
def PF_R_D:        u32 = 4u32;

def DT_NULL:       i64 = 0i64;
def DT_NEEDED:     i64 = 1i64;
def DT_PLTRELSZ:   i64 = 2i64;
def DT_PLTGOT:     i64 = 3i64;
def DT_HASH:       i64 = 4i64;
def DT_STRTAB:     i64 = 5i64;
def DT_SYMTAB:     i64 = 6i64;
def DT_STRSZ:      i64 = 10i64;
def DT_SYMENT:     i64 = 11i64;
def DT_PLTREL:     i64 = 20i64;
def DT_RELA:       i64 = 7i64;
def DT_JMPREL:     i64 = 23i64;
def DT_BIND_NOW:   i64 = 24i64;
def DT_VERSYM:     i64 = 1879048176i64;	// 0x6ffffff0
def DT_VERNEED:    i64 = 1879048190i64;	// 0x6ffffffe
def DT_VERNEEDNUM: i64 = 1879048191i64;	// 0x6fffffff

def VER_NDX_LOCAL_D:  u16 = 0u16;
def VER_NDX_GLOBAL_D: u16 = 1u16;

def R_X86_64_PC32_D:        i32 = 2;
def R_X86_64_PLT32_D:       i32 = 4;
def R_X86_64_JUMP_SLOT_D:   u32 = 7u32;

def STB_GLOBAL_D: u8 = 1u8;
def STT_FUNC_D:   u8 = 2u8;

def PLT_STUB_BYTES_D: u64 = 8u64;
def PAGE: u64 = 4096u64;

def INTERP: str = "/lib64/ld-linux-x86-64.so.2";

// ---- byte writers ------------------------------------------------------

fn dwr8(buf: *u8, off: u64, v: u8) void = {
	buf[off] = v;
};

fn dwr16(buf: *u8, off: u64, v: u16) void = {
	buf[off]         = (v & 255u16): u8;
	buf[off + 1u64]  = ((v >> 8u16) & 255u16): u8;
};

fn dwr32(buf: *u8, off: u64, v: u32) void = {
	buf[off]         = (v & 255u32): u8;
	buf[off + 1u64]  = ((v >> 8u32)  & 255u32): u8;
	buf[off + 2u64]  = ((v >> 16u32) & 255u32): u8;
	buf[off + 3u64]  = ((v >> 24u32) & 255u32): u8;
};

fn dwr64(buf: *u8, off: u64, v: u64) void = {
	dwr32(buf, off,        (v & 4294967295u64): u32);
	dwr32(buf, off + 4u64, ((v >> 32u64) & 4294967295u64): u32);
};

fn dwri64(buf: *u8, off: u64, v: i64) void = {
	dwr64(buf, off, v: u64);
};

fn dwri32(buf: *u8, off: u64, v: i32) void = {
	dwr32(buf, off, v: u32);
};

// ---- byte readers ------------------------------------------------------

fn drdu16(p: *u8, off: u64) u16 = {
	let b0: u16 = p[off]: u16;
	let b1: u16 = p[off + 1u64]: u16;
	return b0 | (b1 << 8u16);
};

fn drdu32(p: *u8, off: u64) u32 = {
	let b0: u32 = p[off]: u32;
	let b1: u32 = p[off + 1u64]: u32;
	let b2: u32 = p[off + 2u64]: u32;
	let b3: u32 = p[off + 3u64]: u32;
	return b0 | (b1 << 8u32) | (b2 << 16u32) | (b3 << 24u32);
};

fn drdi32(p: *u8, off: u64) i32 = {
	return drdu32(p, off): i32;
};

fn dbcopy(dst: *u8, off: u64, src: *u8, n: u64) void = {
	let i: u64 = 0u64;
	for (i < n) {
		dst[off + i] = src[i];
		i += 1u64;
	};
};

// elfhash — SysV ELF hash. Used for .gnu.version_r's vna_hash.
fn elfhash(name: str) u32 = {
	let h: u32 = 0u32;
	let i: i32 = 0;
	for (i < name.len) {
		let c: u32 = (name[i]: u8): u32;
		h = (h << 4u32) + c;
		let g: u32 = h & 4026531840u32;	// 0xf0000000
		if (g != 0u32) { h = h ^ (g >> 24u32); };
		h = h & ~g;
		i += 1;
	};
	return h;
};

fn alignup(off: u64, a: u64) u64 = {
	return (off + a - 1u64) & ~(a - 1u64);
};

fn streqd(a: str, b: str) bool = {
	if (a.len != b.len) { return false; };
	let i: i32 = 0;
	for (i < a.len) {
		if (a[i] != b[i]) { return false; };
		i += 1;
	};
	return true;
};

// ---- main entry --------------------------------------------------------

export fn emitdynelf(l: *lnk, fd: i32, base: u64, entry: u64) i32 = {
	// .data shares the R+W PT_LOAD with .got.plt and .dynamic.
	// Placed after .dynamic so the segment is one contiguous run;
	// relocate runs from here so the dyn layout's datava lands in
	// patched offsets.
	let a: *arena = l.a;
	let n: i32 = l.dynn;
	let nu: u64 = n: u64;

	// ---- collect dyn syms into a plt_idx-indexed array ----
	let dynsyms: **lsym = amalloc(a, nu * 8u64): **lsym;
	let s: *lsym = l.syms;
	for (s != nil) {
		if (s.isdyn != 0) {
			if (s.pltidx >= 0) {
				if (s.pltidx < n) {
					dynsyms[s.pltidx] = s;
				};
			};
		};
		s = s.snext;
	};
	let i: i32 = 0;
	for (i < n) {
		if (dynsyms[i] == nil) {
			os.write(2, "w6l: dynout: no sym for plt_idx\n".ptr, 31u64);
			return 1;
		};
		i += 1;
	};

	// ---- collect used .so's (in l.sos order) ----
	let maxsos: i32 = 0;
	let so: *lso = l.sos;
	for (so != nil) { maxsos += 1; so = so.sonext; };
	let sosused: **lso = amalloc(a, (maxsos: u64) * 8u64): **lso;
	let nsos: i32 = 0;
	so = l.sos;
	for (so != nil) {
		let used: i32 = 0;
		let j: i32 = 0;
		for (j < n) {
			let dsm: *lsym = dynsyms[j];
			let dl: *lso = dsm.dynlib;
			if (dl == so) { used = 1; j = n; }
			else { j += 1; };
		};
		if (used != 0) {
			sosused[nsos] = so;
			nsos += 1;
		};
		so = so.sonext;
	};

	// ---- build flat version table grouped by vlib ----
	// vlib_sos_idx[k] = sos_used index for vlib k.
	// vlib_first[k]   = ver index of first version under vlib k.
	// vlib_count[k]   = number of versions under vlib k.
	// ver_lib_idx[v]  = vlib index that version v belongs to.
	// ver_name_ptr_arr[v] = name's *u8 (interned in the .so's verdef strings).
	// ver_name_len_buf[v] = name length (i32).
	// ver_dynstr_off[v]   = offset within .dynstr (assigned after layout).
	// ver_vna_other[v]    = versym index (starting at 2).

	let vlibsosidxbuf: *u8 = amalloc(a, (maxsos: u64) * 4u64): *u8;
	let vlibfirstbuf:   *u8 = amalloc(a, (maxsos: u64) * 4u64): *u8;
	let vlibcountbuf:   *u8 = amalloc(a, (maxsos: u64) * 4u64): *u8;
	let nvlibs: i32 = 0;

	let verlibidxbuf:  *u8 = amalloc(a, nu * 4u64): *u8;
	let vernameptrarr: **u8 = amalloc(a, nu * 8u64): **u8;
	let vernamelenbuf: *u8 = amalloc(a, nu * 4u64): *u8;
	let verdynstroff:   *u8 = amalloc(a, nu * 4u64): *u8;
	let vervnaother:    *u8 = amalloc(a, nu * 2u64): *u8;
	let nvers: i32 = 0;

	let si: i32 = 0;
	for (si < nsos) {
		let curso: *lso = sosused[si];
		let has: i32 = 0;
		let j: i32 = 0;
		for (j < n) {
			let dsm: *lsym = dynsyms[j];
			let dl: *lso = dsm.dynlib;
			if (dl == curso) {
				let nm0: str = dsm.name;
				let dv: str = soversion(curso, nm0);
				if (dv.len > 0) {
					has = 1; j = n;
				} else { j += 1; };
			} else { j += 1; };
		};
		if (has != 0) {
			dwr32(vlibsosidxbuf, (nvlibs: u64) * 4u64, si: u32);
			dwr32(vlibfirstbuf,   (nvlibs: u64) * 4u64, nvers: u32);
			let added: i32 = 0;
			let jj: i32 = 0;
			for (jj < n) {
				let dsm2: *lsym = dynsyms[jj];
				let dl2: *lso = dsm2.dynlib;
				if (dl2 == curso) {
					let nm2: str = dsm2.name;
					let vname: str = soversion(curso, nm2);
					if (vname.len > 0) {
						let seen: i32 = 0;
						let k: i32 = 0;
						for (k < added) {
							let kk: i32 = nvers - added + k;
							let existing: str;
							existing.ptr = vernameptrarr[kk];
							existing.len = drdi32(vernamelenbuf, (kk: u64) * 4u64);
							if (streqd(existing, vname)) {
								seen = 1; k = added;
							} else { k += 1; };
						};
						if (seen == 0) {
							dwr32(verlibidxbuf, (nvers: u64) * 4u64, nvlibs: u32);
							vernameptrarr[nvers] = vname.ptr;
							dwri32(vernamelenbuf, (nvers: u64) * 4u64, vname.len);
							nvers += 1;
							added += 1;
						};
					};
				};
				jj += 1;
			};
			dwr32(vlibcountbuf, (nvlibs: u64) * 4u64, added: u32);
			nvlibs += 1;
		};
		si += 1;
	};

	// Assign vna_other indices starting at 2, walking vlib then per-version.
	let nextvna: u16 = 2u16;
	let vi: i32 = 0;
	for (vi < nvlibs) {
		let first: i32 = drdi32(vlibfirstbuf, (vi: u64) * 4u64);
		let cnt:   i32 = drdi32(vlibcountbuf, (vi: u64) * 4u64);
		let k: i32 = 0;
		for (k < cnt) {
			dwr16(vervnaother, ((first + k): u64) * 2u64, nextvna);
			nextvna += 1u16;
			k += 1;
		};
		vi += 1;
	};

	// ---- compute dynstr size ----
	let dynstrsz: u64 = 1u64;	// leading NUL
	let pi: i32 = 0;
	for (pi < nsos) {
		let so4: *lso = sosused[pi];
		dynstrsz += so4.soname.len: u64;
		dynstrsz += 1u64;
		pi += 1;
	};
	pi = 0;
	for (pi < n) {
		let dsm4: *lsym = dynsyms[pi];
		dynstrsz += dsm4.name.len: u64;
		dynstrsz += 1u64;
		pi += 1;
	};
	pi = 0;
	for (pi < nvers) {
		let nmlen: i32 = drdi32(vernamelenbuf, (pi: u64) * 4u64);
		dynstrsz += nmlen: u64;
		dynstrsz += 1u64;
		pi += 1;
	};

	// ---- fill dynstr ----
	let dynstr: *u8 = amalloc(a, dynstrsz): *u8;
	let dynstrpos: u64 = 1u64;	// past leading NUL

	let sonamestr: *u8 = amalloc(a, (nsos: u64) * 4u64): *u8;
	pi = 0;
	for (pi < nsos) {
		dwr32(sonamestr, (pi: u64) * 4u64, dynstrpos: u32);
		let so2: *lso = sosused[pi];
		let snm: str = so2.soname;
		dbcopy(dynstr, dynstrpos, snm.ptr, snm.len: u64);
		dynstrpos += snm.len: u64;
		dynstr[dynstrpos] = 0u8;
		dynstrpos += 1u64;
		pi += 1;
	};
	let symnamestr: *u8 = amalloc(a, nu * 4u64): *u8;
	pi = 0;
	for (pi < n) {
		dwr32(symnamestr, (pi: u64) * 4u64, dynstrpos: u32);
		let dsm: *lsym = dynsyms[pi];
		let snm: str = dsm.name;
		dbcopy(dynstr, dynstrpos, snm.ptr, snm.len: u64);
		dynstrpos += snm.len: u64;
		dynstr[dynstrpos] = 0u8;
		dynstrpos += 1u64;
		pi += 1;
	};
	pi = 0;
	for (pi < nvers) {
		dwr32(verdynstroff, (pi: u64) * 4u64, dynstrpos: u32);
		let nmp: *u8 = vernameptrarr[pi];
		let nmlen: i32 = drdi32(vernamelenbuf, (pi: u64) * 4u64);
		dbcopy(dynstr, dynstrpos, nmp, nmlen: u64);
		dynstrpos += nmlen: u64;
		dynstr[dynstrpos] = 0u8;
		dynstrpos += 1u64;
		pi += 1;
	};

	// ---- per-dyn-sym versym index ----
	let versymfor: *u8 = amalloc(a, nu * 2u64): *u8;
	pi = 0;
	for (pi < n) {
		let dsm3: *lsym = dynsyms[pi];
		let dl3: *lso = dsm3.dynlib;
		let nm3: str = dsm3.name;
		let vname: str = soversion(dl3, nm3);
		if (vname.len == 0) {
			dwr16(versymfor, (pi: u64) * 2u64, VER_NDX_GLOBAL_D);
		} else {
			let matched: i32 = 0;
			let vk: i32 = 0;
			for (vk < nvers) {
				let vlx:  i32 = drdi32(verlibidxbuf, (vk: u64) * 4u64);
				let sosx: i32 = drdi32(vlibsosidxbuf, (vlx: u64) * 4u64);
				if (sosused[sosx] == dl3) {
					let exi: str;
					exi.ptr = vernameptrarr[vk];
					exi.len = drdi32(vernamelenbuf, (vk: u64) * 4u64);
					if (streqd(exi, vname)) {
						let other: u16 = drdu16(vervnaother, (vk: u64) * 2u64);
						dwr16(versymfor, (pi: u64) * 2u64, other);
						matched = 1;
						vk = nvers;
					} else { vk += 1; };
				} else { vk += 1; };
			};
			if (matched == 0) {
				dwr16(versymfor, (pi: u64) * 2u64, VER_NDX_GLOBAL_D);
			};
		};
		pi += 1;
	};

	// ---- compute byte sizes ----
	let ehdrsz: u64 = 64u64;
	let nphdrs: u64 = 4u64;
	let phdrsz: u64 = nphdrs * 56u64;
	let interpsz: u64 = (INTERP.len: u64) + 1u64;

	let nsymstotal: u64 = 1u64 + nu;
	let dynsymsz: u64 = nsymstotal * 24u64;

	let nbuckets: u32 = 1u32;
	let nchain: u32 = nsymstotal: u32;
	let hashsz: u64 = (2u64 + (nbuckets: u64) + (nchain: u64)) * 4u64;

	let relapltsz: u64 = nu * 24u64;
	let pltsz: u64 = nu * PLT_STUB_BYTES_D;
	let gotpltsz: u64 = (3u64 + nu) * 8u64;
	let versymsz: u64 = nsymstotal * 2u64;

	let verneedsz: u64 = 0u64;
	let vli: i32 = 0;
	for (vli < nvlibs) {
		let cnt: i32 = drdi32(vlibcountbuf, (vli: u64) * 4u64);
		verneedsz += 16u64 + 16u64 * (cnt: u64);
		vli += 1;
	};

	let withver: i32 = 0;
	if (nvlibs > 0) { withver = 1; };
	let extra: u64 = 0u64;
	if (withver != 0) { extra = 3u64; };
	let ndyn: u64 = (nsos: u64) + 11u64 + extra;
	let dynamicsz: u64 = ndyn * 16u64;

	// ---- compute file offsets ----
	let off: u64 = ehdrsz + phdrsz;
	let interpoff: u64 = off;       off += interpsz;
	off = alignup(off, 8u64);
	let dynstroff: u64 = off;       off += dynstrsz;
	off = alignup(off, 8u64);
	let dynsymoff: u64 = off;       off += dynsymsz;
	let hashoff: u64 = off;         off += hashsz;
	off = alignup(off, 2u64);
	let versymoff: u64 = off;       off += versymsz;
	off = alignup(off, 4u64);
	let verneedoff: u64 = off;      off += verneedsz;
	off = alignup(off, 8u64);
	let relapltoff: u64 = off;      off += relapltsz;

	let textoff: u64 = alignup(off, PAGE);
	let pltoff: u64 = textoff + l.textlen;
	let rxend: u64 = pltoff + pltsz;

	let gotpltoff: u64 = alignup(rxend, PAGE);
	let dynamicoff: u64 = gotpltoff + gotpltsz;
	let dataoff: u64 = dynamicoff + dynamicsz;
	let fileend: u64 = dataoff + l.datalen;

	let interpva: u64 = base + interpoff;
	let dynstrva: u64 = base + dynstroff;
	let dynsymva: u64 = base + dynsymoff;
	let hashva: u64 = base + hashoff;
	let versymva: u64 = base + versymoff;
	let verneedva: u64 = base + verneedoff;
	let relapltva: u64 = base + relapltoff;
	let textva: u64 = base + textoff;
	let pltva: u64 = base + pltoff;
	let gotpltva: u64 = base + gotpltoff;
	let dynamicva: u64 = base + dynamicoff;
	let datava: u64 = base + dataoff;

	// Apply relocations now that the dyn layout's textva/datava are
	// pinned. main.ww defers this so each path uses its own VAs.
	if (relocate(l, textva, datava) != 0) { return 1; };

	// BSS optimisation — same trailing-zero scan as out.ww.
	let bsslen: u64 = 0u64;
	if (l.datalen > 0u64) {
		for (bsslen < l.datalen) {
			let b: u8 = l.data[l.datalen - 1u64 - bsslen];
			if (b != 0u8) { break; };
			bsslen += 1u64;
		};
	};
	let datafilelen: u64 = l.datalen - bsslen;
	let filedataend: u64 = dataoff + datafilelen;

	// ---- build .dynsym ----
	let dynsymbuf: *u8 = amalloc(a, dynsymsz): *u8;
	pi = 0;
	for (pi < n) {
		let eoff: u64 = (1u64 + (pi: u64)) * 24u64;
		dwr32(dynsymbuf, eoff + 0u64, drdu32(symnamestr, (pi: u64) * 4u64));
		dwr8(dynsymbuf, eoff + 4u64, (STB_GLOBAL_D << 4u8) | (STT_FUNC_D & 15u8));
		dwr8(dynsymbuf, eoff + 5u64, 0u8);
		dwr16(dynsymbuf, eoff + 6u64, 0u16);
		dwr64(dynsymbuf, eoff + 8u64, 0u64);
		dwr64(dynsymbuf, eoff + 16u64, 0u64);
		pi += 1;
	};

	// ---- build .hash (SysV, 1 bucket) ----
	let hashbuf: *u8 = amalloc(a, hashsz): *u8;
	dwr32(hashbuf, 0u64, nbuckets);
	dwr32(hashbuf, 4u64, nchain);
	let bucket0: u32 = 0u32;
	if (nsymstotal > 1u64) { bucket0 = 1u32; };
	dwr32(hashbuf, 8u64, bucket0);
	let ci: u64 = 1u64;
	for (ci < nsymstotal) {
		let nxt: u32 = 0u32;
		if (ci + 1u64 < nsymstotal) { nxt = (ci + 1u64): u32; };
		dwr32(hashbuf, 8u64 + (nbuckets: u64) * 4u64 + ci * 4u64, nxt);
		ci += 1u64;
	};

	// ---- build .rela.plt ----
	let relapltbuf: *u8 = amalloc(a, relapltsz): *u8;
	pi = 0;
	for (pi < n) {
		let roff: u64 = (pi: u64) * 24u64;
		dwr64(relapltbuf, roff + 0u64, gotpltva + (3u64 + (pi: u64)) * 8u64);
		let info: u64 = ((1u64 + (pi: u64)) << 32u64) | (R_X86_64_JUMP_SLOT_D: u64);
		dwr64(relapltbuf, roff + 8u64, info);
		dwri64(relapltbuf, roff + 16u64, 0i64);
		pi += 1;
	};

	// ---- build .gnu.version (u16 per dynsym entry) ----
	let versymbuf: *u8 = amalloc(a, versymsz): *u8;
	dwr16(versymbuf, 0u64, VER_NDX_LOCAL_D);
	pi = 0;
	for (pi < n) {
		dwr16(versymbuf, 2u64 + (pi: u64) * 2u64, drdu16(versymfor, (pi: u64) * 2u64));
		pi += 1;
	};

	// ---- build .gnu.version_r ----
	let verneedbuf: *u8 = amalloc(a, verneedsz): *u8;
	if (verneedsz > 0u64) {
		let vnoff: u64 = 0u64;
		vli = 0;
		for (vli < nvlibs) {
			let sosidx: i32 = drdi32(vlibsosidxbuf, (vli: u64) * 4u64);
			let first:   i32 = drdi32(vlibfirstbuf,   (vli: u64) * 4u64);
			let cnt:     i32 = drdi32(vlibcountbuf,   (vli: u64) * 4u64);
			let vnstart: u64 = vnoff;
			dwr16(verneedbuf, vnoff + 0u64, 1u16);
			dwr16(verneedbuf, vnoff + 2u64, cnt: u16);
			dwr32(verneedbuf, vnoff + 4u64, drdu32(sonamestr, (sosidx: u64) * 4u64));
			dwr32(verneedbuf, vnoff + 8u64, 16u32);
			vnoff += 16u64;
			let k: i32 = 0;
			for (k < cnt) {
				let vk: i32 = first + k;
				let nm: str;
				nm.ptr = vernameptrarr[vk];
				nm.len = drdi32(vernamelenbuf, (vk: u64) * 4u64);
				let h: u32 = elfhash(nm);
				dwr32(verneedbuf, vnoff + 0u64, h);
				dwr16(verneedbuf, vnoff + 4u64, 0u16);
				dwr16(verneedbuf, vnoff + 6u64, drdu16(vervnaother, (vk: u64) * 2u64));
				dwr32(verneedbuf, vnoff + 8u64, drdu32(verdynstroff, (vk: u64) * 4u64));
				let nxt: u32 = 0u32;
				if (k + 1 < cnt) { nxt = 16u32; };
				dwr32(verneedbuf, vnoff + 12u64, nxt);
				vnoff += 16u64;
				k += 1;
			};
			let vnnxt: u32 = 0u32;
			if (vli + 1 < nvlibs) { vnnxt = (vnoff - vnstart): u32; };
			dwr32(verneedbuf, vnstart + 12u64, vnnxt);
			vli += 1;
		};
	};

	// ---- build .plt ----
	let pltbuf: *u8 = amalloc(a, pltsz): *u8;
	pi = 0;
	for (pi < n) {
		let poff: u64 = (pi: u64) * PLT_STUB_BYTES_D;
		let stubva: u64 = pltva + poff;
		let nextip: u64 = stubva + 6u64;
		let slotva: u64 = gotpltva + (3u64 + (pi: u64)) * 8u64;
		let disp: i64 = (slotva: i64) - (nextip: i64);
		dwr8(pltbuf, poff + 0u64, 255u8);
		dwr8(pltbuf, poff + 1u64, 37u8);
		dwr32(pltbuf, poff + 2u64, (disp: i32): u32);
		pi += 1;
	};

	// ---- build .got.plt ----
	let gotpltbuf: *u8 = amalloc(a, gotpltsz): *u8;
	dwr64(gotpltbuf, 0u64, dynamicva);

	// ---- build .dynamic ----
	let dynamicbuf: *u8 = amalloc(a, dynamicsz): *u8;
	let dk: u64 = 0u64;
	pi = 0;
	for (pi < nsos) {
		dwri64(dynamicbuf, dk * 16u64 + 0u64, DT_NEEDED);
		dwr64(dynamicbuf, dk * 16u64 + 8u64, drdu32(sonamestr, (pi: u64) * 4u64): u64);
		dk += 1u64;
		pi += 1;
	};
	dwri64(dynamicbuf, dk * 16u64, DT_HASH);     dwr64(dynamicbuf, dk * 16u64 + 8u64, hashva);     dk += 1u64;
	dwri64(dynamicbuf, dk * 16u64, DT_STRTAB);   dwr64(dynamicbuf, dk * 16u64 + 8u64, dynstrva);   dk += 1u64;
	dwri64(dynamicbuf, dk * 16u64, DT_SYMTAB);   dwr64(dynamicbuf, dk * 16u64 + 8u64, dynsymva);   dk += 1u64;
	dwri64(dynamicbuf, dk * 16u64, DT_STRSZ);    dwr64(dynamicbuf, dk * 16u64 + 8u64, dynstrsz);   dk += 1u64;
	dwri64(dynamicbuf, dk * 16u64, DT_SYMENT);   dwr64(dynamicbuf, dk * 16u64 + 8u64, 24u64);       dk += 1u64;
	dwri64(dynamicbuf, dk * 16u64, DT_PLTGOT);   dwr64(dynamicbuf, dk * 16u64 + 8u64, gotpltva);   dk += 1u64;
	dwri64(dynamicbuf, dk * 16u64, DT_PLTRELSZ); dwr64(dynamicbuf, dk * 16u64 + 8u64, relapltsz);  dk += 1u64;
	dwri64(dynamicbuf, dk * 16u64, DT_PLTREL);   dwr64(dynamicbuf, dk * 16u64 + 8u64, DT_RELA: u64);dk += 1u64;
	dwri64(dynamicbuf, dk * 16u64, DT_JMPREL);   dwr64(dynamicbuf, dk * 16u64 + 8u64, relapltva);  dk += 1u64;
	dwri64(dynamicbuf, dk * 16u64, DT_BIND_NOW); dwr64(dynamicbuf, dk * 16u64 + 8u64, 0u64);        dk += 1u64;
	if (withver != 0) {
		dwri64(dynamicbuf, dk * 16u64, DT_VERSYM);     dwr64(dynamicbuf, dk * 16u64 + 8u64, versymva);   dk += 1u64;
		dwri64(dynamicbuf, dk * 16u64, DT_VERNEED);    dwr64(dynamicbuf, dk * 16u64 + 8u64, verneedva);  dk += 1u64;
		dwri64(dynamicbuf, dk * 16u64, DT_VERNEEDNUM); dwr64(dynamicbuf, dk * 16u64 + 8u64, nvlibs: u64);dk += 1u64;
	};
	dwri64(dynamicbuf, dk * 16u64, DT_NULL); dwr64(dynamicbuf, dk * 16u64 + 8u64, 0u64); dk += 1u64;
	if (dk != ndyn) {
		os.write(2, "w6l: dynamic entry count mismatch\n".ptr, 33u64);
		return 1;
	};

	// ---- patch .text relocs targeting dynamic syms ----
	let r: *lrel = l.rels;
	for (r != nil) {
		if (r.sym != nil) {
			let rsym: *lsym = r.sym;
			if (rsym.isdyn != 0) {
				if (r.kind != R_X86_64_PC32_D) {
					if (r.kind != R_X86_64_PLT32_D) {
						os.write(2, "w6l: dynamic reloc kind unsupported\n".ptr, 35u64);
						return 1;
					};
				};
				let site: u64 = textva + r.off;
				let stub: u64 = pltva + (rsym.pltidx: u64) * PLT_STUB_BYTES_D;
				let disp: i64 = (stub: i64) - (site: i64) + r.addend;
				dwr32(l.text, r.off, (disp: i32): u32);
			};
		};
		r = r.rnext;
	};

	// ---- assemble file buffer ----
	let filebuf: *u8 = rt.malloc(fileend): *u8;
	if (filebuf == nil) {
		os.write(2, "w6l: out of memory\n".ptr, 18u64);
		return 1;
	};

	// Ehdr
	dwr8(filebuf, 0u64, 127u8);
	dwr8(filebuf, 1u64, 69u8);
	dwr8(filebuf, 2u64, 76u8);
	dwr8(filebuf, 3u64, 70u8);
	dwr8(filebuf, 4u64, ELFCLASS64_D);
	dwr8(filebuf, 5u64, ELFDATA2LSB_D);
	dwr8(filebuf, 6u64, EV_CURRENT_D: u8);
	dwr16(filebuf, 16u64, ET_EXEC_D);
	dwr16(filebuf, 18u64, EM_X86_64_D);
	dwr32(filebuf, 20u64, EV_CURRENT_D);
	dwr64(filebuf, 24u64, entry);
	dwr64(filebuf, 32u64, ehdrsz);
	dwr64(filebuf, 40u64, 0u64);
	dwr32(filebuf, 48u64, 0u32);
	dwr16(filebuf, 52u64, ehdrsz: u16);
	dwr16(filebuf, 54u64, 56u16);
	dwr16(filebuf, 56u64, nphdrs: u16);
	dwr16(filebuf, 58u64, 0u16);
	dwr16(filebuf, 60u64, 0u16);
	dwr16(filebuf, 62u64, 0u16);

	// Phdrs at offset 64.
	let p0: u64 = 64u64;
	dwr32(filebuf, p0 + 0u64,  PT_LOAD_D);
	dwr32(filebuf, p0 + 4u64,  PF_R_D | PF_X_D);
	dwr64(filebuf, p0 + 8u64,  0u64);
	dwr64(filebuf, p0 + 16u64, base);
	dwr64(filebuf, p0 + 24u64, base);
	dwr64(filebuf, p0 + 32u64, rxend);
	dwr64(filebuf, p0 + 40u64, rxend);
	dwr64(filebuf, p0 + 48u64, PAGE);

	let p1: u64 = 64u64 + 56u64;
	dwr32(filebuf, p1 + 0u64,  PT_LOAD_D);
	dwr32(filebuf, p1 + 4u64,  PF_R_D | PF_W_D);
	dwr64(filebuf, p1 + 8u64,  gotpltoff);
	dwr64(filebuf, p1 + 16u64, gotpltva);
	dwr64(filebuf, p1 + 24u64, gotpltva);
	// filesz trims the .data trailing zeros (BSS); memsz covers
	// .got.plt + .dynamic + the full .data so the loader zero-fills.
	dwr64(filebuf, p1 + 32u64, filedataend - gotpltoff);
	dwr64(filebuf, p1 + 40u64, fileend - gotpltoff);
	dwr64(filebuf, p1 + 48u64, PAGE);

	let p2: u64 = 64u64 + 112u64;
	dwr32(filebuf, p2 + 0u64,  PT_INTERP_D);
	dwr32(filebuf, p2 + 4u64,  PF_R_D);
	dwr64(filebuf, p2 + 8u64,  interpoff);
	dwr64(filebuf, p2 + 16u64, interpva);
	dwr64(filebuf, p2 + 24u64, interpva);
	dwr64(filebuf, p2 + 32u64, interpsz);
	dwr64(filebuf, p2 + 40u64, interpsz);
	dwr64(filebuf, p2 + 48u64, 1u64);

	let p3: u64 = 64u64 + 168u64;
	dwr32(filebuf, p3 + 0u64,  PT_DYNAMIC_D);
	dwr32(filebuf, p3 + 4u64,  PF_R_D | PF_W_D);
	dwr64(filebuf, p3 + 8u64,  dynamicoff);
	dwr64(filebuf, p3 + 16u64, dynamicva);
	dwr64(filebuf, p3 + 24u64, dynamicva);
	dwr64(filebuf, p3 + 32u64, dynamicsz);
	dwr64(filebuf, p3 + 40u64, dynamicsz);
	dwr64(filebuf, p3 + 48u64, 8u64);

	// Sections.
	dbcopy(filebuf, interpoff, INTERP.ptr, INTERP.len: u64);
	dwr8(filebuf, interpoff + (INTERP.len: u64), 0u8);
	dbcopy(filebuf, dynstroff, dynstr, dynstrsz);
	dbcopy(filebuf, dynsymoff, dynsymbuf, dynsymsz);
	dbcopy(filebuf, hashoff, hashbuf, hashsz);
	dbcopy(filebuf, versymoff, versymbuf, versymsz);
	if (verneedsz > 0u64) {
		dbcopy(filebuf, verneedoff, verneedbuf, verneedsz);
	};
	dbcopy(filebuf, relapltoff, relapltbuf, relapltsz);
	if (l.textlen > 0u64) {
		dbcopy(filebuf, textoff, l.text, l.textlen);
	};
	dbcopy(filebuf, pltoff, pltbuf, pltsz);
	dbcopy(filebuf, gotpltoff, gotpltbuf, gotpltsz);
	dbcopy(filebuf, dynamicoff, dynamicbuf, dynamicsz);
	if (datafilelen > 0u64) {
		dbcopy(filebuf, dataoff, l.data, datafilelen);
	};

	let wr: (i64 | os.oserror) = os.writeall(fd, filebuf, filedataend);
	match (wr) {
	case let v: i64 => { if (v != filedataend: i64) { return 1; }; };
	case let e: os.oserror => return 1;
	};
	return 0;
};

// selfhost/cmd/w6l/out.ww — port of cmd/w6l/out.c.
//
// Emit a static ELF64 executable. File layout (per the C original):
//   [0..64)       Ehdr
//   [64..120)     Phdr (one PT_LOAD)
//   [120..0x1000) zero pad
//   [0x1000..)    .text bytes
// Single PT_LOAD covers the whole file, R+X. No interpreter, no .bss.

package w6l;

import os;
import rt;
import sym;
import dynout;

def ET_EXEC:    u16 = 2u16;
def EM_X86_64_W: u16 = 62u16;
def EV_CURRENT: u32 = 1u32;
def ELFCLASS64: u8 = 2u8;
def ELFDATA2LSB: u8 = 1u8;
def PT_LOAD:    u32 = 1u32;
def PF_X:       u32 = 1u32;
def PF_W:       u32 = 2u32;
def PF_R:       u32 = 4u32;

def TEXT_OFF: u64 = 4096u64;	// 0x1000
def PAGE_SZ:  u64 = 4096u64;

// ---- little-endian byte writers ----------------------------------------

fn wru16(buf: *u8, off: u64, v: u16) void = {
	buf[off]         = (v & 255u16): u8;
	buf[off + 1u64]  = ((v >> 8u16) & 255u16): u8;
};

fn wru32(buf: *u8, off: u64, v: u32) void = {
	buf[off]         = (v & 255u32): u8;
	buf[off + 1u64]  = ((v >> 8u32)  & 255u32): u8;
	buf[off + 2u64]  = ((v >> 16u32) & 255u32): u8;
	buf[off + 3u64]  = ((v >> 24u32) & 255u32): u8;
};

fn wru64(buf: *u8, off: u64, v: u64) void = {
	wru32(buf, off,        (v & 4294967295u64): u32);
	wru32(buf, off + 4u64, ((v >> 32u64) & 4294967295u64): u32);
};

// ---- emit ---------------------------------------------------------------

export fn emitelf(l: *lnk, fd: i32, base: u64, entry: u64) i32 = {
	// Dispatch: any loaded shared object plus any dynamic ref means
	// we owe the loader a real PT_INTERP/PT_DYNAMIC binary.
	if (l.sos != nil) {
		if (l.dynn > 0) {
			return emitdynelf(l, fd, base, entry);
		};
	};

	let hasdata: bool = l.datalen > 0u64;
	let rxend:  u64 = TEXT_OFF + l.textlen;
	// .data lands at the next page boundary so the loader can give
	// it fresh R+W permissions without overlapping the R+X mapping.
	let dataoff: u64 = 0u64;
	let datava: u64 = 0u64;
	if (hasdata) {
		dataoff = (rxend + PAGE_SZ - 1u64) & ~(PAGE_SZ - 1u64);
		datava = base + dataoff;
	};

	// Apply relocations now that the layout's textva/datava are
	// known. Deferred from main.ww so the dyn path uses its own
	// datava.
	if (relocate(l, base + TEXT_OFF, datava) != 0) { return -1; };

	// BSS optimisation: trailing zero bytes in .data can be left
	// out of the file. The loader zero-fills the gap between
	// p_filesz and p_memsz. Scan after l_relocate has applied any
	// DATAR patches — anything still zero at the tail genuinely is
	// zero-init. Matches cmd/w6l/out.c byte-for-byte.
	let bsslen: u64 = 0u64;
	if (hasdata) {
		for (bsslen < l.datalen) {
			let b: u8 = l.data[l.datalen - 1u64 - bsslen];
			if (b != 0u8) { break; };
			bsslen += 1u64;
		};
	};
	let datafilelen: u64 = l.datalen - bsslen;

	// One contiguous header buffer covering [0..0x1000), then .text.
	let hdr: *u8 = rt.malloc(TEXT_OFF): *u8;	// zero-initialised by mmap

	// --- Ehdr (64 bytes) ---
	hdr[0u64] = 127u8;	// 0x7f
	hdr[1u64] = 69u8;	// 'E'
	hdr[2u64] = 76u8;	// 'L'
	hdr[3u64] = 70u8;	// 'F'
	hdr[4u64] = ELFCLASS64;
	hdr[5u64] = ELFDATA2LSB;
	hdr[6u64] = EV_CURRENT: u8;
	wru16(hdr, 16u64, ET_EXEC);		// e_type
	wru16(hdr, 18u64, EM_X86_64_W);	// e_machine
	wru32(hdr, 20u64, EV_CURRENT);		// e_version
	wru64(hdr, 24u64, entry);		// e_entry
	wru64(hdr, 32u64, 64u64);		// e_phoff = sizeof(Ehdr)
	wru64(hdr, 40u64, 0u64);		// e_shoff
	wru32(hdr, 48u64, 0u32);		// e_flags
	wru16(hdr, 52u64, 64u16);		// e_ehsize
	wru16(hdr, 54u64, 56u16);		// e_phentsize
	if (hasdata) { wru16(hdr, 56u64, 2u16); }
	else { wru16(hdr, 56u64, 1u16); };
	wru16(hdr, 58u64, 0u16);		// e_shentsize
	wru16(hdr, 60u64, 0u16);		// e_shnum
	wru16(hdr, 62u64, 0u16);		// e_shstrndx

	// --- Phdr #1 (R+X) at offset 64 ---
	wru32(hdr, 64u64, PT_LOAD);
	wru32(hdr, 68u64, PF_R | PF_X);
	wru64(hdr, 72u64, 0u64);		// p_offset
	wru64(hdr, 80u64, base);		// p_vaddr
	wru64(hdr, 88u64, base);		// p_paddr
	wru64(hdr, 96u64, rxend);		// p_filesz
	wru64(hdr, 104u64, rxend);		// p_memsz
	wru64(hdr, 112u64, TEXT_OFF);		// p_align

	if (hasdata) {
		// --- Phdr #2 (R+W) at offset 64+56=120 ---
		wru32(hdr, 120u64, PT_LOAD);
		wru32(hdr, 124u64, PF_R | PF_W);
		wru64(hdr, 128u64, dataoff);		// p_offset
		wru64(hdr, 136u64, base + dataoff);	// p_vaddr
		wru64(hdr, 144u64, base + dataoff);	// p_paddr
		wru64(hdr, 152u64, datafilelen);	// p_filesz
		wru64(hdr, 160u64, l.datalen);		// p_memsz
		wru64(hdr, 168u64, PAGE_SZ);		// p_align
	};

	// Write [0..0x1000) then .text.
	let r1: (i64 | os.oserror) = os.writeall(fd, hdr, TEXT_OFF);
	let n1: i64 = 0i64;
	match (r1) {
	case let v: i64 => n1 = v;
	case let e: os.oserror => return -1;
	};
	if (n1 != TEXT_OFF: i64) { return -1; };
	if (l.textlen > 0u64) {
		let r2: (i64 | os.oserror) = os.writeall(fd, l.text, l.textlen);
		let n2: i64 = 0i64;
		match (r2) {
		case let v: i64 => n2 = v;
		case let e: os.oserror => return -1;
		};
		if (n2 != l.textlen: i64) { return -1; };
	};
	if (hasdata && datafilelen > 0u64) {
		// Pad to the page-aligned data offset, then write only
		// the non-zero prefix of .data. The rest is BSS — the
		// loader zero-fills from p_filesz to p_memsz.
		let here: u64 = TEXT_OFF + l.textlen;
		let zero: u8 = 0u8;
		for (here < dataoff) {
			let r3: (i64 | os.oserror) = os.writeall(fd, &zero, 1u64);
			match (r3) {
			case let v: i64 => { };
			case let e: os.oserror => return -1;
			};
			here += 1u64;
		};
		let r4: (i64 | os.oserror) = os.writeall(fd, l.data, datafilelen);
		let n4: i64 = 0i64;
		match (r4) {
		case let v: i64 => n4 = v;
		case let e: os.oserror => return -1;
		};
		if (n4 != datafilelen: i64) { return -1; };
	};
	return 0;
};

// selfhost/cmd/w6l/main.ww — port of cmd/w6l/main.c.
//
// w6l = amd64 linker. Reads relocatable ELF .o files, SysV `ar`
// archives, and shared objects (ET_DYN). Resolves symbols, applies
// relocations, writes a static or dynamic-linked ELF executable.
//
//   w6l_ww -o out [-L<dir>...] [-l<name>...] file1.o file2.o ...

package main;

import os;
import rt;
import mem;
import sym;
import obj;
import dyn;
import pass;
import out;

def BASE: u64 = 4194304u64;	// 0x400000
def CODE_VA_OFF: u64 = 4096u64;	// .text starts at base + 0x1000

fn mklnk(a: *arena) *lnk = {
	let l: *lnk = alloc(lnk { a = a })!;
	return l;
};

// `cstreq` lives in obj.ww — same bundle, single definition.

// `cstrlen` lives in obj.ww — same bundle, single definition.

// Build "<dir>/lib<name>.<ext>" into dst (NUL-terminated). Returns total
// length excluding NUL. dst must be large enough.
fn buildpath(dst: *u8, dir: *u8, name: *u8, ext: str) u64 = {
	let i: u64 = 0u64;
	let dn: u64 = cstrlen(dir);
	let nn: u64 = cstrlen(name);
	let k: u64 = 0u64;
	for (k < dn) { dst[i] = dir[k]; i += 1u64; k += 1u64; };
	dst[i] = 47u8;	// '/'
	i += 1u64;
	dst[i] = 108u8;	// 'l'
	i += 1u64;
	dst[i] = 105u8;	// 'i'
	i += 1u64;
	dst[i] = 98u8;	// 'b'
	i += 1u64;
	k = 0u64;
	for (k < nn) { dst[i] = name[k]; i += 1u64; k += 1u64; };
	k = 0u64;
	for (k < ext.len: u64) {
		let li: i32 = k: i32;
		dst[i] = ext[li];
		i += 1u64;
		k += 1u64;
	};
	dst[i] = 0u8;
	return i;
};

// Append decimal n to dst at offset i. Returns new offset.
fn appenddec(dst: *u8, i: u64, n: u64) u64 = {
	if (n == 0u64) {
		dst[i] = 48u8;
		return i + 1u64;
	};
	let buf: *u8 = rt.malloc(16u64): *u8;
	let k: u64 = 0u64;
	let v: u64 = n;
	for (v > 0u64) {
		buf[k] = (v % 10u64): u8 + 48u8;
		v = v / 10u64;
		k += 1u64;
	};
	let oi: u64 = i;
	for (k > 0u64) {
		k -= 1u64;
		dst[oi] = buf[k];
		oi += 1u64;
	};
	return oi;
};

fn buildpathv(dst: *u8, dir: *u8, name: *u8, v: u64) u64 = {
	let i: u64 = 0u64;
	let dn: u64 = cstrlen(dir);
	let nn: u64 = cstrlen(name);
	let k: u64 = 0u64;
	for (k < dn) { dst[i] = dir[k]; i += 1u64; k += 1u64; };
	dst[i] = 47u8; i += 1u64;
	dst[i] = 108u8; i += 1u64;
	dst[i] = 105u8; i += 1u64;
	dst[i] = 98u8; i += 1u64;
	k = 0u64;
	for (k < nn) { dst[i] = name[k]; i += 1u64; k += 1u64; };
	dst[i] = 46u8; i += 1u64; dst[i] = 115u8; i += 1u64; dst[i] = 111u8; i += 1u64; dst[i] = 46u8; i += 1u64;
	i = appenddec(dst, i, v);
	dst[i] = 0u8;
	return i;
};

// islinkable: read first 8 bytes; require !<arch>\n or \x7fELF.
fn islinkable(path: *u8) bool = {
	let fd: i32 = os.open(pathstr(path), os.flag.RDONLY, 0i32);
	if (fd < 0) { return false; };
	let mp: *u8 = rt.malloc(8u64): *u8;
	let n: i64 = os.read(fd, mp, 8u64);
	os.close(fd);
	if (n < 4i64) { return false; };
	// archive: "!<arch>\n"
	if (n >= 8i64) {
		if (mp[0u64] == 33u8) { if (mp[1u64] == 60u8) {
		if (mp[2u64] == 97u8) { if (mp[3u64] == 114u8) {
		if (mp[4u64] == 99u8) { if (mp[5u64] == 104u8) {
		if (mp[6u64] == 62u8) { if (mp[7u64] == 10u8) {
			return true;
		}; }; }; }; }; }; }; };
	};
	// ELF: "\x7fELF"
	if (mp[0u64] == 127u8) {
		if (mp[1u64] == 69u8) {
			if (mp[2u64] == 76u8) {
				if (mp[3u64] == 70u8) { return true; };
			};
		};
	};
	return false;
};

// Walk libdirs[0..n) trying lib<name>.so, then lib<name>.so.{0..8},
// then lib<name>.a. Return arena-owned NUL-terminated path on success,
// nil on miss.
fn resolvelib(a: *arena, name: *u8, libdirs: **u8, nlibdirs: i32) *u8 = {
	let bufp: *u8 = rt.malloc(1024u64): *u8;
	let i: i32 = 0;
	for (i < nlibdirs) {
		let dir: *u8 = libdirs[i];
		let _l1: u64 = buildpath(bufp, dir, name, ".so");
		if (islinkable(bufp)) {
			let pl: u64 = cstrlen(bufp);
			let p: *u8 = amalloc(a, pl + 1u64): *u8;
			let k: u64 = 0u64;
			for (k <= pl) { p[k] = bufp[k]; k += 1u64; };
			return p;
		};
		let v: u64 = 0u64;
		for (v <= 8u64) {
			let _l2: u64 = buildpathv(bufp, dir, name, v);
			if (islinkable(bufp)) {
				let pl2: u64 = cstrlen(bufp);
				let p2: *u8 = amalloc(a, pl2 + 1u64): *u8;
				let k2: u64 = 0u64;
				for (k2 <= pl2) { p2[k2] = bufp[k2]; k2 += 1u64; };
				return p2;
			};
			v += 1u64;
		};
		let _l3: u64 = buildpath(bufp, dir, name, ".a");
		if (islinkable(bufp)) {
			let pl3: u64 = cstrlen(bufp);
			let p3: *u8 = amalloc(a, pl3 + 1u64): *u8;
			let k3: u64 = 0u64;
			for (k3 <= pl3) { p3[k3] = bufp[k3]; k3 += 1u64; };
			return p3;
		};
		i += 1;
	};
	return nil;
};

// Read first 20 bytes; return 1 for ET_DYN .so, 0 for ar/.o.
fn isso(path: *u8) i32 = {
	let fd: i32 = os.open(pathstr(path), os.flag.RDONLY, 0i32);
	if (fd < 0) { return 0; };
	let mp: *u8 = rt.malloc(20u64): *u8;
	let n: i64 = os.read(fd, mp, 20u64);
	os.close(fd);
	if (n < 20i64) { return 0; };
	if (mp[0u64] != 127u8) { return 0; };
	if (mp[1u64] != 69u8) { return 0; };
	if (mp[2u64] != 76u8) { return 0; };
	if (mp[3u64] != 70u8) { return 0; };
	// e_type at offset 16, u16 little-endian
	let t: u16 = (mp[16u64]: u16) | ((mp[17u64]: u16) << 8u16);
	if (t == 3u16) { return 1; };
	return 0;
};

export fn main(argc: i32, argv: **u8) i32 = {
	let outpath: *u8 = nil;
	let maxinputs: i32 = 64;
	let inputs:  **u8 = rt.malloc((maxinputs: u64) * 8u64): **u8;
	let ninputs: i32 = 0;
	let libdirs: **u8 = rt.malloc((maxinputs: u64) * 8u64): **u8;
	let nlibdirs: i32 = 0;
	let lflags:  **u8 = rt.malloc((maxinputs: u64) * 8u64): **u8;
	let nlflags: i32 = 0;

	let i: i32 = 1;
	for (i < argc) {
		let a: *u8 = argv[i];
		if (cstreq(a, "-o")) {
			i += 1;
			if (i >= argc) {
				os.write(2, "w6l: -o requires argument\n".ptr, 25u64);
				return 2;
			};
			outpath = argv[i];
		} else { if (cstreq(a, "-L")) {
			i += 1;
			if (i >= argc) {
				os.write(2, "w6l: -L requires argument\n".ptr, 25u64);
				return 2;
			};
			libdirs[nlibdirs] = argv[i];
			nlibdirs += 1;
		} else { if (cstreq(a, "-l")) {
			i += 1;
			if (i >= argc) {
				os.write(2, "w6l: -l requires argument\n".ptr, 25u64);
				return 2;
			};
			lflags[nlflags] = argv[i];
			nlflags += 1;
		} else { if (a[0u64] == 45u8) {
			// -L<dir> joined form.
			if (a[1u64] == 76u8) {
				if (a[2u64] != 0u8) {
					libdirs[nlibdirs] = a + 2u64;
					nlibdirs += 1;
				} else {
					os.write(2, "w6l: bare -L\n".ptr, 12u64);
					return 2;
				};
			} else { if (a[1u64] == 108u8) {
				if (a[2u64] != 0u8) {
					lflags[nlflags] = a + 2u64;
					nlflags += 1;
				} else {
					os.write(2, "w6l: bare -l\n".ptr, 12u64);
					return 2;
				};
			} else {
				os.write(2, "w6l: unknown flag\n".ptr, 17u64);
				return 2;
			};};
		} else {
			if (ninputs >= maxinputs) {
				os.write(2, "w6l: too many inputs\n".ptr, 20u64);
				return 2;
			};
			inputs[ninputs] = a;
			ninputs += 1;
		};};};};
		i += 1;
	};

	if (outpath == nil) {
		os.write(2, "usage: w6l_ww -o exe [-L<dir>...] [-l<name>...] file1.o [file2.o...]\n".ptr, 68u64);
		return 2;
	};
	if (ninputs == 0) {
		os.write(2, "w6l: no inputs\n".ptr, 14u64);
		return 2;
	};

	let a: *arena = newarena();
	let l: *lnk = mklnk(a);

	// Seed _start so libwwrt-style start.o is recognised as wanted.
	intern(l, "_start");

	// Load positional inputs first (preserving order).
	let k: i32 = 0;
	for (k < ninputs) {
		if (load(l, inputs[k]) != 0) {
			return 1;
		};
		k += 1;
	};

	// Then resolve -l flags and load each. Archives append; shared
	// objects register their exports.
	let lf: i32 = 0;
	for (lf < nlflags) {
		let p: *u8 = resolvelib(a, lflags[lf], libdirs, nlibdirs);
		if (p == nil) {
			os.write(2, "w6l: cannot find -l".ptr, 18u64);
			let nm: *u8 = lflags[lf];
			os.write(2, nm, cstrlen(nm));
			os.write(2, "\n".ptr, 1u64);
			return 1;
		};
		if (isso(p) != 0) {
			if (loadso(l, p) != 0) { return 1; };
		} else {
			if (load(l, p) != 0) { return 1; };
		};
		lf += 1;
	};

	if (resolve(l) != 0) { return 1; };
	// Relocation is deferred to the emit functions — each path
	// knows its own layout (textva, datava); the static and dyn
	// paths place .data at different VAs.

	let entrysym: *lsym = lookup(l, "_start");
	if (entrysym == nil) { entrysym = lookup(l, "main"); }
	else { if (entrysym.defined == 0) { entrysym = lookup(l, "main"); }; };
	if (entrysym == nil) {
		os.write(2, "w6l: no _start or main symbol\n".ptr, 29u64);
		return 1;
	};
	if (entrysym.defined == 0) {
		os.write(2, "w6l: no _start or main symbol\n".ptr, 29u64);
		return 1;
	};

	let flags: os.flag = os.flag.WRONLY | os.flag.CREATE | os.flag.TRUNC;
	let fd: i32 = os.open(pathstr(outpath), flags, 493i32);	// 0o755
	if (fd < 0) {
		os.write(2, "w6l: cannot open output\n".ptr, 23u64);
		return 1;
	};

	let entryva: u64 = BASE + CODE_VA_OFF + entrysym.val;
	let rc: i32 = emitelf(l, fd, BASE, entryva);
	os.close(fd);
	return rc;
};