Commit 4d6429fc4fd299cdfb2256d4aac87bc6551ba09e | zig

author	Pat Tullmann <pat.github@tullmann.org> 2024-07-31 22:49:39-07:00
committer	Andrew Kelley <andrew@ziglang.org> 2024-08-07 13:05:42-07:00
log	4d6429fc4fd299cdfb2256d4aac87bc6551ba09e
tree	8b7de21ad01c27119b19a0b18b0cf962f418c985
parent	979fd12be96d5f8eda3e02ba676aecea78e6c0db

POSIX link() syscall only takes two arguments (no flags)

The signature is documented as:

   int link(const char *, const char *);

(see https://man7.org/linux/man-pages/man2/link.2.html or https://man.netbsd.org/link.2)

And its not some Linux extension, the [syscall
implementation](https://github.com/torvalds/linux/blob/21b136cc63d2a9ddd60d4699552b69c214b32964/fs/namei.c#L4794-L4797)
only expects two arguments too.

It probably *should* have a flags parameter, but its too late now.

I am a bit surprised that linking glibc or musl against code that invokes
a 'link' with three parameters doesn't fail (at least, I couldn't get any
local test cases to trigger a compile or link error).

The test case in std/posix/test.zig is currently disabled, but if I
manually enable it, it works with this change.

4 files changed, 11 insertions(+), 12 deletions(-)

lib
- std
  - c.zig
  - os
    linux.zig
  - posix.zig
  - posix
    test.zig

lib/std/c.zig+1-1

...	...	@@ -9060,7 +9060,7 @@ pub extern "c" fn pwrite(fd: fd_t, buf: [*]const u8, nbyte: usize, offset: off_t
9060	9060	pub extern "c" fn mmap(addr: ?align(page_size) anyopaque, len: usize, prot: c_uint, flags: MAP, fd: fd_t, offset: off_t) anyopaque;
9061	9061	pub extern "c" fn munmap(addr: *align(page_size) const anyopaque, len: usize) c_int;
9062	9062	pub extern "c" fn mprotect(addr: *align(page_size) anyopaque, len: usize, prot: c_uint) c_int;
9063		pub extern "c" fn link(oldpath: [:0]const u8, newpath: [:0]const u8, flags: c_int) c_int;
	9063	pub extern "c" fn link(oldpath: [:0]const u8, newpath: [:0]const u8) c_int;
9064	9064	pub extern "c" fn linkat(oldfd: fd_t, oldpath: [:0]const u8, newfd: fd_t, newpath: [:0]const u8, flags: c_int) c_int;
9065	9065	pub extern "c" fn unlink(path: [*:0]const u8) c_int;
9066	9066	pub extern "c" fn unlinkat(dirfd: fd_t, path: [*:0]const u8, flags: c_uint) c_int;

lib/std/os/linux.zig+3-4

...	...	@@ -1339,13 +1339,12 @@ pub fn tgkill(tgid: pid_t, tid: pid_t, sig: i32) usize {
1339	1339	return syscall3(.tgkill, @as(usize, @bitCast(@as(isize, tgid))), @as(usize, @bitCast(@as(isize, tid))), @as(usize, @bitCast(@as(isize, sig))));
1340	1340	}
1341	1341
1342		pub fn link(oldpath: [:0]const u8, newpath: [:0]const u8, flags: i32) usize {
	1342	pub fn link(oldpath: [:0]const u8, newpath: [:0]const u8) usize {
1343	1343	if (@hasField(SYS, "link")) {
1344		return syscall3(
	1344	return syscall2(
1345	1345	.link,
1346	1346	@intFromPtr(oldpath),
1347	1347	@intFromPtr(newpath),
1348		@as(usize, @bitCast(@as(isize, flags))),
1349	1348	);
1350	1349	} else {
1351	1350	return syscall5(
...	...	@@ -1354,7 +1353,7 @@ pub fn link(oldpath: [:0]const u8, newpath: [:0]const u8, flags: i32) usize {
1354	1353	@intFromPtr(oldpath),
1355	1354	@as(usize, @bitCast(@as(isize, AT.FDCWD))),
1356	1355	@intFromPtr(newpath),
1357		@as(usize, @bitCast(@as(isize, flags))),
	1356	0,
1358	1357	);
1359	1358	}
1360	1359	}

lib/std/posix.zig+6-6

...	...	@@ -2202,11 +2202,11 @@ pub const LinkError = UnexpectedError \|\| error{
2202	2202
2203	2203	/// On WASI, both paths should be encoded as valid UTF-8.
2204	2204	/// On other platforms, both paths are an opaque sequence of bytes with no particular encoding.
2205		pub fn linkZ(oldpath: [:0]const u8, newpath: [:0]const u8, flags: i32) LinkError!void {
	2205	pub fn linkZ(oldpath: [:0]const u8, newpath: [:0]const u8) LinkError!void {
2206	2206	if (native_os == .wasi and !builtin.link_libc) {
2207		return link(mem.sliceTo(oldpath, 0), mem.sliceTo(newpath, 0), flags);
	2207	return link(mem.sliceTo(oldpath, 0), mem.sliceTo(newpath, 0));
2208	2208	}
2209		switch (errno(system.link(oldpath, newpath, flags))) {
	2209	switch (errno(system.link(oldpath, newpath))) {
2210	2210	.SUCCESS => return,
2211	2211	.ACCES => return error.AccessDenied,
2212	2212	.DQUOT => return error.DiskQuota,
...	...	@@ -2233,16 +2233,16 @@ pub fn linkZ(oldpath: [:0]const u8, newpath: [:0]const u8, flags: i32) LinkErr
2233	2233
2234	2234	/// On WASI, both paths should be encoded as valid UTF-8.
2235	2235	/// On other platforms, both paths are an opaque sequence of bytes with no particular encoding.
2236		pub fn link(oldpath: []const u8, newpath: []const u8, flags: i32) LinkError!void {
	2236	pub fn link(oldpath: []const u8, newpath: []const u8) LinkError!void {
2237	2237	if (native_os == .wasi and !builtin.link_libc) {
2238		return linkat(wasi.AT.FDCWD, oldpath, wasi.AT.FDCWD, newpath, flags) catch \|err\| switch (err) {
	2238	return linkat(wasi.AT.FDCWD, oldpath, wasi.AT.FDCWD, newpath, 0) catch \|err\| switch (err) {
2239	2239	error.NotDir => unreachable, // link() does not support directories
2240	2240	else => \|e\| return e,
2241	2241	};
2242	2242	}
2243	2243	const old = try toPosixPath(oldpath);
2244	2244	const new = try toPosixPath(newpath);
2245		return try linkZ(&old, &new, flags);
	2245	return try linkZ(&old, &new);
2246	2246	}
2247	2247
2248	2248	pub const LinkatError = LinkError \|\| error{NotDir};

lib/std/posix/test.zig+1-1

...	...	@@ -278,7 +278,7 @@ test "link with relative paths" {
278	278	cwd.deleteFile("new.txt") catch {};
279	279
280	280	try cwd.writeFile(.{ .sub_path = "example.txt", .data = "example" });
281		try posix.link("example.txt", "new.txt", 0);
	281	try posix.link("example.txt", "new.txt");
282	282
283	283	const efd = try cwd.openFile("example.txt", .{});
284	284	defer efd.close();