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WASI: remove absolute path emulation from std lib

Browse source 
Instead of checking for absolute paths and current working directories
in various file system operations, there is one simple solution: allow
overriding `std.fs.cwd` on WASI.

os.realpath is back to causing a compile error when used on WASI. This
caused a compile error in the Sema handling of `@src()`. The compiler
should never call realpath, so the commit that made this change is
reverted (95ab942184). If this breaks
debug info, a different strategy is needed to solve it other than using
realpath.

I also removed the preopens code and replaced it with something much
simpler. There is no longer any global state in the standard library.

Additionally-
 * os.openat no longer does an unnecessary fstat on WASI when O.WRONLY
   is not provided.
 * os.chdir is back to causing a compile error on WASI.
This commit is contained in:
Andrew Kelley 2022-11-10 13:50:44 -07:00
parent 0a2fdfbdb9
commit d5312d53a0
6 changed files with 145 additions and 547 deletions
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35
lib/std/fs.zig
View file

@ -1130,13 +1130,6 @@ pub const Dir = struct {
w.RIGHT.FD_FILESTAT_SET_TIMES |
w.RIGHT.FD_FILESTAT_SET_SIZE;
}
if (self.fd == os.wasi.AT.FDCWD or path.isAbsolute(sub_path)) {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var resolved_path_buf: [MAX_PATH_BYTES]u8 = undefined;
const resolved_path = try os.resolvePathWasi(sub_path, &resolved_path_buf);
const fd = try os.openatWasi(resolved_path.dir_fd, resolved_path.relative_path, 0x0, 0x0, fdflags, base, 0x0);
return File{ .handle = fd };
}
const fd = try os.openatWasi(self.fd, sub_path, 0x0, 0x0, fdflags, base, 0x0);
return File{ .handle = fd };
}
@ -1301,13 +1294,6 @@ pub const Dir = struct {
if (flags.exclusive) {
oflags |= w.O.EXCL;
}
if (self.fd == os.wasi.AT.FDCWD or path.isAbsolute(sub_path)) {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var resolved_path_buf: [MAX_PATH_BYTES]u8 = undefined;
const resolved_path = try os.resolvePathWasi(sub_path, &resolved_path_buf);
const fd = try os.openatWasi(resolved_path.dir_fd, resolved_path.relative_path, 0x0, oflags, 0x0, base, 0x0);
return File{ .handle = fd };
}
const fd = try os.openatWasi(self.fd, sub_path, 0x0, oflags, 0x0, base, 0x0);
return File{ .handle = fd };
}
@ -1711,16 +1697,15 @@ pub const Dir = struct {
// TODO do we really need all the rights here?
const inheriting: w.rights_t = w.RIGHT.ALL ^ w.RIGHT.SOCK_SHUTDOWN;
const result = blk: {
if (self.fd == os.wasi.AT.FDCWD or path.isAbsolute(sub_path)) {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var resolved_path_buf: [MAX_PATH_BYTES]u8 = undefined;
const resolved_path = try os.resolvePathWasi(sub_path, &resolved_path_buf);
break :blk os.openatWasi(resolved_path.dir_fd, resolved_path.relative_path, symlink_flags, w.O.DIRECTORY, 0x0, base, inheriting);
} else {
break :blk os.openatWasi(self.fd, sub_path, symlink_flags, w.O.DIRECTORY, 0x0, base, inheriting);
}
};
const result = os.openatWasi(
self.fd,
sub_path,
symlink_flags,
w.O.DIRECTORY,
0x0,
base,
inheriting,
);
const fd = result catch |err| switch (err) {
error.FileTooBig => unreachable, // can't happen for directories
error.IsDir => unreachable, // we're providing O.DIRECTORY
@ -2667,6 +2652,8 @@ pub const Dir = struct {
pub fn cwd() Dir {
if (builtin.os.tag == .windows) {
return Dir{ .fd = os.windows.peb().ProcessParameters.CurrentDirectory.Handle };
} else if (builtin.os.tag == .wasi and @hasDecl(root, "wasi_cwd")) {
return root.wasi_cwd();
} else {
return Dir{ .fd = os.AT.FDCWD };
}

305
lib/std/fs/wasi.zig
View file

@ -10,284 +10,47 @@ const wasi = std.os.wasi;
const fd_t = wasi.fd_t;
const prestat_t = wasi.prestat_t;
/// Type-tag of WASI preopen.
///
/// WASI currently offers only `Dir` as a valid preopen resource.
pub const PreopenTypeTag = enum {
Dir,
};
pub const Preopens = struct {
// Indexed by file descriptor number.
names: []const []const u8,
/// Type of WASI preopen.
///
/// WASI currently offers only `Dir` as a valid preopen resource.
pub const PreopenType = union(PreopenTypeTag) {
/// Preopened directory type.
Dir: []const u8,
const Self = @This();
pub fn eql(self: Self, other: PreopenType) bool {
if (std.meta.activeTag(self) != std.meta.activeTag(other)) return false;
switch (self) {
PreopenTypeTag.Dir => |this_path| return mem.eql(u8, this_path, other.Dir),
}
}
// Checks whether `other` refers to a subdirectory of `self` and, if so,
// returns the relative path to `other` from `self`
//
// Expects `other` to be a canonical path, not containing "." or ".."
pub fn getRelativePath(self: Self, other: PreopenType) ?[]const u8 {
if (std.meta.activeTag(self) != std.meta.activeTag(other)) return null;
switch (self) {
PreopenTypeTag.Dir => |self_path| {
const other_path = other.Dir;
if (mem.indexOfDiff(u8, self_path, other_path)) |index| {
if (index < self_path.len) return null;
}
const rel_path = other_path[self_path.len..];
if (rel_path.len == 0) {
return rel_path;
} else if (rel_path[0] == '/') {
return rel_path[1..];
} else {
if (self_path[self_path.len - 1] != '/') return null;
return rel_path;
}
},
}
}
pub fn format(self: Self, comptime fmt: []const u8, options: std.fmt.FormatOptions, out_stream: anytype) !void {
if (fmt.len != 0) std.fmt.invalidFmtError(fmt, self);
_ = options;
try out_stream.print("PreopenType{{ ", .{});
switch (self) {
PreopenType.Dir => |path| try out_stream.print(".Dir = '{}'", .{std.zig.fmtId(path)}),
}
return out_stream.print(" }}", .{});
}
};
/// WASI preopen struct. This struct consists of a WASI file descriptor
/// and type of WASI preopen. It can be obtained directly from the WASI
/// runtime using `PreopenList.populate()` method.
pub const Preopen = struct {
/// WASI file descriptor.
fd: fd_t,
/// Type of the preopen.
type: PreopenType,
/// Construct new `Preopen` instance.
pub fn new(fd: fd_t, preopen_type: PreopenType) Preopen {
return Preopen{
.fd = fd,
.type = preopen_type,
};
}
};
/// WASI resource identifier struct. This is effectively a path within
/// a WASI Preopen.
pub const PreopenUri = struct {
/// WASI Preopen containing the resource.
base: Preopen,
/// Path to resource within `base`.
relative_path: []const u8,
};
/// Dynamically-sized array list of WASI preopens. This struct is a
/// convenience wrapper for issuing `std.os.wasi.fd_prestat_get` and
/// `std.os.wasi.fd_prestat_dir_name` syscalls to the WASI runtime, and
/// collecting the returned preopens.
///
/// This struct is intended to be used in any WASI program which intends
/// to use the capabilities as passed on by the user of the runtime.
pub const PreopenList = struct {
const InnerList = std.ArrayList(Preopen);
/// Internal dynamically-sized buffer for storing the gathered preopens.
buffer: InnerList,
const Self = @This();
pub const Error = error{ OutOfMemory, Overflow } || os.UnexpectedError;
/// Deinitialize with `deinit`.
pub fn init(allocator: Allocator) Self {
return Self{ .buffer = InnerList.init(allocator) };
}
/// Release all allocated memory.
pub fn deinit(pm: Self) void {
for (pm.buffer.items) |preopen| {
switch (preopen.type) {
PreopenType.Dir => |path| pm.buffer.allocator.free(path),
}
}
pm.buffer.deinit();
}
/// Populate the list with the preopens by issuing `std.os.wasi.fd_prestat_get`
/// and `std.os.wasi.fd_prestat_dir_name` syscalls to the runtime.
///
/// If called more than once, it will clear its contents every time before
/// issuing the syscalls.
///
/// In the unlinkely event of overflowing the number of available file descriptors,
/// returns `error.Overflow`. In this case, even though an error condition was reached
/// the preopen list still contains all valid preopened file descriptors that are valid
/// for use. Therefore, it is fine to call `find`, `asSlice`, or `toOwnedSlice`. Finally,
/// `deinit` still must be called!
///
/// Usage of `cwd_root`:
/// If provided, `cwd_root` is inserted as prefix for any Preopens that
/// begin with "." and all paths are normalized as POSIX-style absolute
/// paths. `cwd_root` must be an absolute path.
///
/// For example:
/// "./foo/bar" -> "{cwd_root}/foo/bar"
/// "foo/bar" -> "/foo/bar"
/// "/foo/bar" -> "/foo/bar"
///
/// If `cwd_root` is not provided, all preopen directories are unmodified.
///
pub fn populate(self: *Self, cwd_root: ?[]const u8) Error!void {
if (cwd_root) |root| assert(fs.path.isAbsolute(root));
// Clear contents if we're being called again
for (try self.toOwnedSlice()) |preopen| {
switch (preopen.type) {
PreopenType.Dir => |path| self.buffer.allocator.free(path),
}
}
errdefer self.deinit();
var fd: fd_t = 3; // start fd has to be beyond stdio fds
var path_buf: [fs.MAX_PATH_BYTES]u8 = undefined;
while (true) {
var buf: prestat_t = undefined;
switch (wasi.fd_prestat_get(fd, &buf)) {
.SUCCESS => {},
.OPNOTSUPP => {
// not a preopen, so keep going
fd = try math.add(fd_t, fd, 1);
continue;
},
.BADF => {
// OK, no more fds available
break;
},
else => |err| return os.unexpectedErrno(err),
}
const preopen_len = buf.u.dir.pr_name_len;
mem.set(u8, path_buf[0..preopen_len], 0);
switch (wasi.fd_prestat_dir_name(fd, &path_buf, preopen_len)) {
.SUCCESS => {},
else => |err| return os.unexpectedErrno(err),
}
// Unfortunately, WASI runtimes (e.g. wasmer) are not consistent about whether the
// NULL sentinel is included in the reported Preopen name_len
const raw_path = if (path_buf[preopen_len - 1] == 0) blk: {
break :blk path_buf[0 .. preopen_len - 1];
} else path_buf[0..preopen_len];
// If we were provided a CWD root to resolve against, we try to treat Preopen dirs as
// POSIX paths, relative to "/" or `cwd_root` depending on whether they start with "."
const path = if (cwd_root) |cwd| blk: {
const resolve_paths: []const []const u8 = if (raw_path[0] == '.') &.{ cwd, raw_path } else &.{ "/", raw_path };
break :blk try fs.path.resolve(self.buffer.allocator, resolve_paths);
} else blk: {
// If we were provided no CWD root, we preserve the preopen dir without resolving
break :blk try self.buffer.allocator.dupe(u8, raw_path);
};
errdefer self.buffer.allocator.free(path);
const preopen = Preopen.new(fd, .{ .Dir = path });
try self.buffer.append(preopen);
fd = try math.add(fd_t, fd, 1);
}
}
/// Find a preopen which includes access to `preopen_type`.
///
/// If multiple preopens match the provided resource, the most specific
/// match is returned. More recent preopens take priority, as well.
pub fn findContaining(self: Self, preopen_type: PreopenType) ?PreopenUri {
var best_match: ?PreopenUri = null;
for (self.buffer.items) |preopen| {
if (preopen.type.getRelativePath(preopen_type)) |rel_path| {
if (best_match == null or rel_path.len <= best_match.?.relative_path.len) {
best_match = PreopenUri{
.base = preopen,
.relative_path = if (rel_path.len == 0) "." else rel_path,
};
}
}
}
return best_match;
}
/// Find preopen by fd. If the preopen exists, return it.
/// Otherwise, return `null`.
pub fn findByFd(self: Self, fd: fd_t) ?Preopen {
for (self.buffer.items) |preopen| {
if (preopen.fd == fd) {
return preopen;
pub fn find(p: Preopens, name: []const u8) ?os.fd_t {
for (p.names) |elem_name, i| {
if (mem.eql(u8, elem_name, name)) {
return @intCast(os.fd_t, i);
}
}
return null;
}
/// Find preopen by type. If the preopen exists, return it.
/// Otherwise, return `null`.
pub fn find(self: Self, preopen_type: PreopenType) ?*const Preopen {
for (self.buffer.items) |*preopen| {
if (preopen.type.eql(preopen_type)) {
return preopen;
}
}
return null;
}
/// Return the inner buffer as read-only slice.
pub fn asSlice(self: Self) []const Preopen {
return self.buffer.items;
}
/// The caller owns the returned memory. ArrayList becomes empty.
pub fn toOwnedSlice(self: *Self) ![]Preopen {
return try self.buffer.toOwnedSlice();
}
};
test "extracting WASI preopens" {
if (builtin.os.tag != .wasi or builtin.link_libc) return error.SkipZigTest;
pub fn preopensAlloc(gpa: Allocator) Allocator.Error!Preopens {
var names: std.ArrayListUnmanaged([]const u8) = .{};
defer names.deinit(gpa);
var preopens = PreopenList.init(std.testing.allocator);
defer preopens.deinit();
try names.ensureUnusedCapacity(gpa, 3);
try preopens.populate(null);
const preopen = preopens.find(PreopenType{ .Dir = "." }) orelse unreachable;
try std.testing.expect(preopen.type.eql(PreopenType{ .Dir = "." }));
const po_type1 = PreopenType{ .Dir = "/" };
try std.testing.expect(std.mem.eql(u8, po_type1.getRelativePath(.{ .Dir = "/" }).?, ""));
try std.testing.expect(std.mem.eql(u8, po_type1.getRelativePath(.{ .Dir = "/test/foobar" }).?, "test/foobar"));
const po_type2 = PreopenType{ .Dir = "/test/foo" };
try std.testing.expect(po_type2.getRelativePath(.{ .Dir = "/test/foobar" }) == null);
const po_type3 = PreopenType{ .Dir = "/test" };
try std.testing.expect(std.mem.eql(u8, po_type3.getRelativePath(.{ .Dir = "/test" }).?, ""));
try std.testing.expect(std.mem.eql(u8, po_type3.getRelativePath(.{ .Dir = "/test/" }).?, ""));
try std.testing.expect(std.mem.eql(u8, po_type3.getRelativePath(.{ .Dir = "/test/foo/bar" }).?, "foo/bar"));
names.appendAssumeCapacity("stdin"); // 0
names.appendAssumeCapacity("stdout"); // 1
names.appendAssumeCapacity("stderr"); // 2
while (true) {
const fd = @intCast(wasi.fd_t, names.items.len);
var prestat: prestat_t = undefined;
switch (wasi.fd_prestat_get(fd, &prestat)) {
.SUCCESS => {},
.OPNOTSUPP, .BADF => return .{ .names = names.toOwnedSlice(gpa) },
else => @panic("fd_prestat_get: unexpected error"),
}
try names.ensureUnusedCapacity(gpa, 1);
// This length does not include a null byte. Let's keep it this way to
// gently encourage WASI implementations to behave properly.
const name_len = prestat.u.dir.pr_name_len;
const name = try gpa.alloc(u8, name_len);
errdefer gpa.free(name);
switch (wasi.fd_prestat_dir_name(fd, name.ptr, name.len)) {
.SUCCESS => {},
else => @panic("fd_prestat_dir_name: unexpected error"),
}
names.appendAssumeCapacity(name);
}
}

212
lib/std/os.zig
View file

@ -1521,76 +1521,6 @@ pub fn openW(file_path_w: []const u16, flags: u32, perm: mode_t) OpenError!fd_t
};
}
var wasi_cwd = if (builtin.os.tag == .wasi and !builtin.link_libc) struct {
// List of available Preopens
preopens: ?PreopenList = null,
// Memory buffer for storing the relative portion of the CWD
path_buffer: [MAX_PATH_BYTES]u8 = undefined,
// The absolute path associated with the current working directory
cwd: []const u8 = "/",
}{} else undefined;
/// Initialize the available Preopen list on WASI and set the CWD to `cwd_init`.
/// Note that `cwd_init` corresponds to a Preopen directory, not necessarily
/// a POSIX path. For example, "." matches a Preopen provided with `--dir=.`
///
/// This must be called before using any relative or absolute paths with `std.os`
/// functions, if you are on WASI without linking libc.
///
/// The current working directory is initialized to `cwd_root`, and `cwd_root`
/// is inserted as a prefix for any Preopens whose dir begins with "."
/// For example:
/// "./foo/bar" - canonicalizes to -> "{cwd_root}/foo/bar"
/// "foo/bar" - canonicalizes to -> "/foo/bar"
/// "/foo/bar" - canonicalizes to -> "/foo/bar"
///
/// `cwd_root` must be an absolute path. For initialization behavior similar to
/// wasi-libc, use "/" as the `cwd_root`
///
/// `alloc` must not be a temporary or leak-detecting allocator, since `std.os`
/// retains ownership of allocations internally and may never call free().
pub fn initPreopensWasi(alloc: Allocator, cwd_root: []const u8) !void {
if (builtin.os.tag == .wasi) {
if (!builtin.link_libc) {
var preopen_list = PreopenList.init(alloc);
errdefer preopen_list.deinit();
try preopen_list.populate(cwd_root);
var path_alloc = std.heap.FixedBufferAllocator.init(&wasi_cwd.path_buffer);
wasi_cwd.cwd = try path_alloc.allocator().dupe(u8, cwd_root);
if (wasi_cwd.preopens) |preopens| preopens.deinit();
wasi_cwd.preopens = preopen_list;
} else {
// wasi-libc defaults to an effective CWD root of "/"
if (!mem.eql(u8, cwd_root, "/")) return error.UnsupportedDirectory;
}
}
}
/// Resolve a relative or absolute path to an handle (`fd_t`) and a relative subpath.
///
/// For absolute paths, this automatically searches among available Preopens to find
/// a match. For relative paths, it uses the "emulated" CWD.
/// Automatically looks up the correct Preopen corresponding to the provided path.
pub fn resolvePathWasi(path: []const u8, out_buffer: *[MAX_PATH_BYTES]u8) !RelativePathWasi {
var allocator = std.heap.FixedBufferAllocator.init(out_buffer);
var alloc = allocator.allocator();
const abs_path = fs.path.resolve(alloc, &.{ wasi_cwd.cwd, path }) catch return error.NameTooLong;
const preopen_uri = wasi_cwd.preopens.?.findContaining(.{ .Dir = abs_path });
if (preopen_uri) |po| {
return RelativePathWasi{
.dir_fd = po.base.fd,
.relative_path = po.relative_path,
};
} else {
// No matching preopen found
return error.AccessDenied;
}
}
/// Open and possibly create a file. Keeps trying if it gets interrupted.
/// `file_path` is relative to the open directory handle `dir_fd`.
/// See also `openatZ`.
@ -1600,22 +1530,23 @@ pub fn openat(dir_fd: fd_t, file_path: []const u8, flags: u32, mode: mode_t) Ope
return openatW(dir_fd, file_path_w.span(), flags, mode);
} else if (builtin.os.tag == .wasi and !builtin.link_libc) {
// `mode` is ignored on WASI, which does not support unix-style file permissions
const fd = if (dir_fd == wasi.AT.FDCWD or fs.path.isAbsolute(file_path)) blk: {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var path_buf: [MAX_PATH_BYTES]u8 = undefined;
const path = try resolvePathWasi(file_path, &path_buf);
const opts = try openOptionsFromFlagsWasi(path.dir_fd, flags);
break :blk try openatWasi(path.dir_fd, path.relative_path, opts.lookup_flags, opts.oflags, opts.fs_flags, opts.fs_rights_base, opts.fs_rights_inheriting);
} else blk: {
const opts = try openOptionsFromFlagsWasi(dir_fd, flags);
break :blk try openatWasi(dir_fd, file_path, opts.lookup_flags, opts.oflags, opts.fs_flags, opts.fs_rights_base, opts.fs_rights_inheriting);
};
const opts = try openOptionsFromFlagsWasi(dir_fd, flags);
const fd = try openatWasi(
dir_fd,
file_path,
opts.lookup_flags,
opts.oflags,
opts.fs_flags,
opts.fs_rights_base,
opts.fs_rights_inheriting,
);
errdefer close(fd);
const info = try fstat(fd);
if (flags & O.WRONLY != 0 and info.filetype == .DIRECTORY)
return error.IsDir;
if (flags & O.WRONLY != 0) {
const info = try fstat(fd);
if (info.filetype == .DIRECTORY)
return error.IsDir;
}
return fd;
}
@ -1673,7 +1604,15 @@ fn openOptionsFromFlagsWasi(fd: fd_t, oflag: u32) OpenError!WasiOpenOptions {
}
/// Open and possibly create a file in WASI.
pub fn openatWasi(dir_fd: fd_t, file_path: []const u8, lookup_flags: lookupflags_t, oflags: oflags_t, fdflags: fdflags_t, base: rights_t, inheriting: rights_t) OpenError!fd_t {
pub fn openatWasi(
dir_fd: fd_t,
file_path: []const u8,
lookup_flags: lookupflags_t,
oflags: oflags_t,
fdflags: fdflags_t,
base: rights_t,
inheriting: rights_t,
) OpenError!fd_t {
while (true) {
var fd: fd_t = undefined;
switch (wasi.path_open(dir_fd, lookup_flags, file_path.ptr, file_path.len, oflags, base, inheriting, fdflags, &fd)) {
@ -2031,7 +1970,7 @@ pub fn getcwd(out_buffer: []u8) GetCwdError![]u8 {
if (builtin.os.tag == .windows) {
return windows.GetCurrentDirectory(out_buffer);
} else if (builtin.os.tag == .wasi and !builtin.link_libc) {
const path = wasi_cwd.cwd;
const path = ".";
if (out_buffer.len < path.len) return error.NameTooLong;
std.mem.copy(u8, out_buffer, path);
return out_buffer[0..path.len];
@ -2125,12 +2064,6 @@ pub fn symlinkat(target_path: []const u8, newdirfd: fd_t, sym_link_path: []const
if (builtin.os.tag == .windows) {
@compileError("symlinkat is not supported on Windows; use std.os.windows.CreateSymbolicLink instead");
} else if (builtin.os.tag == .wasi and !builtin.link_libc) {
if (newdirfd == wasi.AT.FDCWD or fs.path.isAbsolute(target_path)) {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var path_buf: [MAX_PATH_BYTES]u8 = undefined;
const path = try resolvePathWasi(sym_link_path, &path_buf);
return symlinkatWasi(target_path, path.dir_fd, path.relative_path);
}
return symlinkatWasi(target_path, newdirfd, sym_link_path);
}
const target_path_c = try toPosixPath(target_path);
@ -2284,25 +2217,8 @@ pub fn linkat(
flags: i32,
) LinkatError!void {
if (builtin.os.tag == .wasi and !builtin.link_libc) {
var resolve_olddir: bool = (olddir == wasi.AT.FDCWD or fs.path.isAbsolute(oldpath));
var resolve_newdir: bool = (newdir == wasi.AT.FDCWD or fs.path.isAbsolute(newpath));
var old: RelativePathWasi = .{ .dir_fd = olddir, .relative_path = oldpath };
var new: RelativePathWasi = .{ .dir_fd = newdir, .relative_path = newpath };
// Resolve absolute or CWD-relative paths to a path within a Preopen
if (resolve_olddir or resolve_newdir) {
var buf_old: [MAX_PATH_BYTES]u8 = undefined;
var buf_new: [MAX_PATH_BYTES]u8 = undefined;
if (resolve_olddir)
old = try resolvePathWasi(oldpath, &buf_old);
if (resolve_newdir)
new = try resolvePathWasi(newpath, &buf_new);
return linkatWasi(old, new, flags);
}
const old: RelativePathWasi = .{ .dir_fd = olddir, .relative_path = oldpath };
const new: RelativePathWasi = .{ .dir_fd = newdir, .relative_path = newpath };
return linkatWasi(old, new, flags);
}
const old = try toPosixPath(oldpath);
@ -2423,12 +2339,6 @@ pub fn unlinkat(dirfd: fd_t, file_path: []const u8, flags: u32) UnlinkatError!vo
const file_path_w = try windows.sliceToPrefixedFileW(file_path);
return unlinkatW(dirfd, file_path_w.span(), flags);
} else if (builtin.os.tag == .wasi and !builtin.link_libc) {
if (dirfd == wasi.AT.FDCWD or fs.path.isAbsolute(file_path)) {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var path_buf: [MAX_PATH_BYTES]u8 = undefined;
const path = try resolvePathWasi(file_path, &path_buf);
return unlinkatWasi(path.dir_fd, path.relative_path, flags);
}
return unlinkatWasi(dirfd, file_path, flags);
} else {
const file_path_c = try toPosixPath(file_path);
@ -2597,24 +2507,8 @@ pub fn renameat(
const new_path_w = try windows.sliceToPrefixedFileW(new_path);
return renameatW(old_dir_fd, old_path_w.span(), new_dir_fd, new_path_w.span(), windows.TRUE);
} else if (builtin.os.tag == .wasi and !builtin.link_libc) {
var resolve_old: bool = (old_dir_fd == wasi.AT.FDCWD or fs.path.isAbsolute(old_path));
var resolve_new: bool = (new_dir_fd == wasi.AT.FDCWD or fs.path.isAbsolute(new_path));
var old: RelativePathWasi = .{ .dir_fd = old_dir_fd, .relative_path = old_path };
var new: RelativePathWasi = .{ .dir_fd = new_dir_fd, .relative_path = new_path };
// Resolve absolute or CWD-relative paths to a path within a Preopen
if (resolve_old or resolve_new) {
var buf_old: [MAX_PATH_BYTES]u8 = undefined;
var buf_new: [MAX_PATH_BYTES]u8 = undefined;
if (resolve_old)
old = try resolvePathWasi(old_path, &buf_old);
if (resolve_new)
new = try resolvePathWasi(new_path, &buf_new);
return renameatWasi(old, new);
}
const old: RelativePathWasi = .{ .dir_fd = old_dir_fd, .relative_path = old_path };
const new: RelativePathWasi = .{ .dir_fd = new_dir_fd, .relative_path = new_path };
return renameatWasi(old, new);
} else {
const old_path_c = try toPosixPath(old_path);
@ -2755,12 +2649,6 @@ pub fn mkdirat(dir_fd: fd_t, sub_dir_path: []const u8, mode: u32) MakeDirError!v
const sub_dir_path_w = try windows.sliceToPrefixedFileW(sub_dir_path);
return mkdiratW(dir_fd, sub_dir_path_w.span(), mode);
} else if (builtin.os.tag == .wasi and !builtin.link_libc) {
if (dir_fd == wasi.AT.FDCWD or fs.path.isAbsolute(sub_dir_path)) {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var path_buf: [MAX_PATH_BYTES]u8 = undefined;
const path = try resolvePathWasi(sub_dir_path, &path_buf);
return mkdiratWasi(path.dir_fd, path.relative_path, mode);
}
return mkdiratWasi(dir_fd, sub_dir_path, mode);
} else {
const sub_dir_path_c = try toPosixPath(sub_dir_path);
@ -2997,22 +2885,7 @@ pub const ChangeCurDirError = error{
/// `dir_path` is recommended to be a UTF-8 encoded string.
pub fn chdir(dir_path: []const u8) ChangeCurDirError!void {
if (builtin.os.tag == .wasi and !builtin.link_libc) {
var buf: [MAX_PATH_BYTES]u8 = undefined;
var alloc = std.heap.FixedBufferAllocator.init(&buf);
const path = fs.path.resolve(alloc.allocator(), &.{ wasi_cwd.cwd, dir_path }) catch |err| switch (err) {
error.OutOfMemory => return error.NameTooLong,
else => |e| return e,
};
const dirinfo = try fstatat(AT.FDCWD, path, 0);
if (dirinfo.filetype != .DIRECTORY) {
return error.NotDir;
}
// This copy is guaranteed to succeed, since buf and path_buffer are the same size.
var cwd_alloc = std.heap.FixedBufferAllocator.init(&wasi_cwd.path_buffer);
wasi_cwd.cwd = cwd_alloc.allocator().dupe(u8, path) catch unreachable;
return;
@compileError("WASI does not support os.chdir");
} else if (builtin.os.tag == .windows) {
var utf16_dir_path: [windows.PATH_MAX_WIDE]u16 = undefined;
const len = try std.unicode.utf8ToUtf16Le(utf16_dir_path[0..], dir_path);
@ -3143,12 +3016,6 @@ pub fn readlinkZ(file_path: [*:0]const u8, out_buffer: []u8) ReadLinkError![]u8
/// See also `readlinkatWasi`, `realinkatZ` and `realinkatW`.
pub fn readlinkat(dirfd: fd_t, file_path: []const u8, out_buffer: []u8) ReadLinkError![]u8 {
if (builtin.os.tag == .wasi and !builtin.link_libc) {
if (dirfd == wasi.AT.FDCWD or fs.path.isAbsolute(file_path)) {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var path_buf: [MAX_PATH_BYTES]u8 = undefined;
var path = try resolvePathWasi(file_path, &path_buf);
return readlinkatWasi(path.dir_fd, path.relative_path, out_buffer);
}
return readlinkatWasi(dirfd, file_path, out_buffer);
}
if (builtin.os.tag == .windows) {
@ -4155,12 +4022,6 @@ pub const FStatAtError = FStatError || error{ NameTooLong, FileNotFound, SymLink
pub fn fstatat(dirfd: fd_t, pathname: []const u8, flags: u32) FStatAtError!Stat {
if (builtin.os.tag == .wasi and !builtin.link_libc) {
const wasi_flags = if (flags & linux.AT.SYMLINK_NOFOLLOW == 0) wasi.LOOKUP_SYMLINK_FOLLOW else 0;
if (dirfd == wasi.AT.FDCWD or fs.path.isAbsolute(pathname)) {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var path_buf: [MAX_PATH_BYTES]u8 = undefined;
const path = try resolvePathWasi(pathname, &path_buf);
return fstatatWasi(path.dir_fd, path.relative_path, wasi_flags);
}
return fstatatWasi(dirfd, pathname, wasi_flags);
} else if (builtin.os.tag == .windows) {
@compileError("fstatat is not yet implemented on Windows");
@ -4556,12 +4417,6 @@ pub fn faccessat(dirfd: fd_t, path: []const u8, mode: u32, flags: u32) AccessErr
var resolved = RelativePathWasi{ .dir_fd = dirfd, .relative_path = path };
const file = blk: {
if (dirfd == wasi.AT.FDCWD or fs.path.isAbsolute(path)) {
// Resolve absolute or CWD-relative paths to a path within a Preopen
var path_buf: [MAX_PATH_BYTES]u8 = undefined;
resolved = resolvePathWasi(path, &path_buf) catch |err| break :blk @as(FStatAtError!Stat, err);
break :blk fstatat(resolved.dir_fd, resolved.relative_path, flags);
}
break :blk fstatat(dirfd, path, flags);
} catch |err| switch (err) {
error.AccessDenied => return error.PermissionDenied,
@ -5147,12 +5002,7 @@ pub fn realpath(pathname: []const u8, out_buffer: *[MAX_PATH_BYTES]u8) RealPathE
const pathname_w = try windows.sliceToPrefixedFileW(pathname);
return realpathW(pathname_w.span(), out_buffer);
} else if (builtin.os.tag == .wasi and !builtin.link_libc) {
var alloc = std.heap.FixedBufferAllocator.init(out_buffer);
// NOTE: This emulation is incomplete. Symbolic links are not
// currently expanded during path canonicalization.
const paths = &.{ wasi_cwd.cwd, pathname };
return fs.path.resolve(alloc.allocator(), paths) catch error.NameTooLong;
@compileError("WASI does not support os.realpath");
}
const pathname_c = try toPosixPath(pathname);
return realpathZ(&pathname_c, out_buffer);

11
src/Sema.zig
View file

@ -15082,14 +15082,11 @@ fn zirBuiltinSrc(
const file_name_val = blk: {
var anon_decl = try block.startAnonDecl();
defer anon_decl.deinit();
const relative_path = try fn_owner_decl.getFileScope().fullPath(sema.arena);
const absolute_path = std.fs.realpathAlloc(sema.arena, relative_path) catch |err| {
return sema.fail(block, src, "failed to get absolute path of file '{s}': {s}", .{ relative_path, @errorName(err) });
};
const aboslute_duped = try anon_decl.arena().dupeZ(u8, absolute_path);
// The compiler must not call realpath anywhere.
const name = try fn_owner_decl.getFileScope().fullPathZ(anon_decl.arena());
const new_decl = try anon_decl.finish(
try Type.Tag.array_u8_sentinel_0.create(anon_decl.arena(), aboslute_duped.len),
try Value.Tag.bytes.create(anon_decl.arena(), aboslute_duped[0 .. aboslute_duped.len + 1]),
try Type.Tag.array_u8_sentinel_0.create(anon_decl.arena(), name.len),
try Value.Tag.bytes.create(anon_decl.arena(), name[0 .. name.len + 1]),
0, // default alignment
);
break :blk try Value.Tag.decl_ref.create(sema.arena, new_decl);

44
src/introspect.zig
View file

@ -37,34 +37,7 @@ fn testZigInstallPrefix(base_dir: fs.Dir) ?Compilation.Directory {
/// based on a hard-coded Preopen directory ("/zig")
pub fn findZigExePath(allocator: mem.Allocator) ![]u8 {
if (builtin.os.tag == .wasi) {
var args = try std.process.argsWithAllocator(allocator);
defer args.deinit();
// On WASI, argv[0] is always just the basename of the current executable
const argv0 = args.next() orelse return error.FileNotFound;
// Check these paths:
// 1. "/zig/{exe_name}"
// 2. "/zig/bin/{exe_name}"
const base_paths_to_check = &[_][]const u8{ "/zig", "/zig/bin" };
const exe_names_to_check = &[_][]const u8{ fs.path.basename(argv0), "zig.wasm" };
for (base_paths_to_check) |base_path| {
for (exe_names_to_check) |exe_name| {
const test_path = fs.path.join(allocator, &.{ base_path, exe_name }) catch continue;
defer allocator.free(test_path);
// Make sure it's a file we're pointing to
const file = os.fstatat(os.wasi.AT.FDCWD, test_path, 0) catch continue;
if (file.filetype != .REGULAR_FILE) continue;
// Path seems to be valid, let's try to turn it into an absolute path
var real_path_buf: [fs.MAX_PATH_BYTES]u8 = undefined;
if (os.realpath(test_path, &real_path_buf)) |real_path| {
return allocator.dupe(u8, real_path); // Success: return absolute path
} else |_| continue;
}
}
return error.FileNotFound;
@compileError("this function is unsupported on WASI");
}
return fs.selfExePathAlloc(allocator);
@ -107,6 +80,9 @@ pub fn findZigLibDirFromSelfExe(
/// Caller owns returned memory.
pub fn resolveGlobalCacheDir(allocator: mem.Allocator) ![]u8 {
if (builtin.os.tag == .wasi) {
@compileError("on WASI the global cache dir must be resolved with preopens");
}
if (std.process.getEnvVarOwned(allocator, "ZIG_GLOBAL_CACHE_DIR")) |value| {
if (value.len > 0) {
return value;
@ -125,17 +101,7 @@ pub fn resolveGlobalCacheDir(allocator: mem.Allocator) ![]u8 {
}
}
if (builtin.os.tag == .wasi) {
// On WASI, we have no way to get an App data dir, so we try to use a fixed
// Preopen path "/cache" as a last resort
const path = "/cache";
const file = os.fstatat(os.wasi.AT.FDCWD, path, 0) catch return error.CacheDirUnavailable;
if (file.filetype != .DIRECTORY) return error.CacheDirUnavailable;
return allocator.dupe(u8, path);
} else {
return fs.getAppDataDir(allocator, appname);
}
return fs.getAppDataDir(allocator, appname);
}
/// Similar to std.fs.path.resolve, with a few important differences:

85
src/main.zig
View file

@ -27,6 +27,23 @@ const crash_report = @import("crash_report.zig");
// Crash report needs to override the panic handler and other root decls
pub usingnamespace crash_report.root_decls;
var wasi_preopens: fs.wasi.Preopens = undefined;
pub inline fn wasi_cwd() fs.Dir {
// Expect the first preopen to be current working directory.
const cwd_fd: std.os.fd_t = 3;
assert(mem.eql(u8, wasi_preopens.names[cwd_fd], "."));
return .{ .fd = cwd_fd };
}
pub fn getWasiPreopen(name: []const u8) Compilation.Directory {
return .{
.path = name,
.handle = .{
.fd = wasi_preopens.find(name) orelse fatal("WASI preopen not found: '{s}'", .{name}),
},
};
}
pub fn fatal(comptime format: []const u8, args: anytype) noreturn {
std.log.err(format, args);
process.exit(1);
@ -161,20 +178,14 @@ pub fn main() anyerror!void {
return mainArgs(gpa_tracy.allocator(), arena, args);
}
// WASI: `--dir` instructs the WASM runtime to "preopen" a directory, making
// it available to the us, the guest program. This is the only way for us to
// access files/dirs on the host filesystem
if (builtin.os.tag == .wasi) {
// This sets our CWD to "/preopens/cwd"
// Dot-prefixed preopens like `--dir=.` are "mounted" at "/preopens/cwd"
// Other preopens like `--dir=lib` are "mounted" at "/"
try std.os.initPreopensWasi(arena, "/preopens/cwd");
wasi_preopens = try fs.wasi.preopensAlloc(arena);
}
// Short circuit some of the other logic for bootstrapping.
if (build_options.only_c) {
assert(mem.eql(u8, args[1], "build-obj"));
return buildOutputType(gpa, arena, args, .{ .build = .Obj });
assert(mem.eql(u8, args[1], "build-exe"));
return buildOutputType(gpa, arena, args, .{ .build = .Exe });
}
return mainArgs(gpa, arena, args);
@ -2300,7 +2311,7 @@ fn buildOutputType(
},
}
if (std.fs.path.isAbsolute(lib_name)) {
if (fs.path.isAbsolute(lib_name)) {
fatal("cannot use absolute path as a system library: {s}", .{lib_name});
}
@ -2763,18 +2774,33 @@ fn buildOutputType(
}
}
const self_exe_path = try introspect.findZigExePath(arena);
var zig_lib_directory: Compilation.Directory = if (override_lib_dir) |unresolved_lib_dir| l: {
const lib_dir = try introspect.resolvePath(arena, unresolved_lib_dir);
break :l .{
.path = lib_dir,
.handle = fs.cwd().openDir(lib_dir, .{}) catch |err| {
fatal("unable to open zig lib directory '{s}': {s}", .{ lib_dir, @errorName(err) });
},
const self_exe_path: ?[]const u8 = if (!process.can_spawn)
null
else
introspect.findZigExePath(arena) catch |err| {
fatal("unable to find zig self exe path: {s}", .{@errorName(err)});
};
} else introspect.findZigLibDirFromSelfExe(arena, self_exe_path) catch |err| {
fatal("unable to find zig installation directory: {s}\n", .{@errorName(err)});
var zig_lib_directory: Compilation.Directory = d: {
if (override_lib_dir) |unresolved_lib_dir| {
const lib_dir = try introspect.resolvePath(arena, unresolved_lib_dir);
break :d .{
.path = lib_dir,
.handle = fs.cwd().openDir(lib_dir, .{}) catch |err| {
fatal("unable to open zig lib directory '{s}': {s}", .{ lib_dir, @errorName(err) });
},
};
} else if (builtin.os.tag == .wasi) {
break :d getWasiPreopen("/lib");
} else if (self_exe_path) |p| {
break :d introspect.findZigLibDirFromSelfExe(arena, p) catch |err| {
fatal("unable to find zig installation directory: {s}", .{@errorName(err)});
};
} else {
unreachable;
}
};
defer zig_lib_directory.handle.close();
var thread_pool: ThreadPool = undefined;
@ -2791,7 +2817,16 @@ fn buildOutputType(
}
var global_cache_directory: Compilation.Directory = l: {
const p = override_global_cache_dir orelse try introspect.resolveGlobalCacheDir(arena);
if (override_global_cache_dir) |p| {
break :l .{
.handle = try fs.cwd().makeOpenPath(p, .{}),
.path = p,
};
}
if (builtin.os.tag == .wasi) {
break :l getWasiPreopen("/cache");
}
const p = try introspect.resolveGlobalCacheDir(arena);
break :l .{
.handle = try fs.cwd().makeOpenPath(p, .{}),
.path = p,
@ -3082,7 +3117,7 @@ fn buildOutputType(
gpa,
arena,
test_exec_args.items,
self_exe_path,
self_exe_path.?,
arg_mode,
target_info,
watch,
@ -3154,7 +3189,7 @@ fn buildOutputType(
gpa,
arena,
test_exec_args.items,
self_exe_path,
self_exe_path.?,
arg_mode,
target_info,
watch,
@ -3179,7 +3214,7 @@ fn buildOutputType(
gpa,
arena,
test_exec_args.items,
self_exe_path,
self_exe_path.?,
arg_mode,
target_info,
watch,
@ -3523,7 +3558,7 @@ fn cmdTranslateC(comp: *Compilation, arena: Allocator, enable_cache: bool) !void
defer tree.deinit(comp.gpa);
if (out_dep_path) |dep_file_path| {
const dep_basename = std.fs.path.basename(dep_file_path);
const dep_basename = fs.path.basename(dep_file_path);
// Add the files depended on to the cache system.
try man.addDepFilePost(zig_cache_tmp_dir, dep_basename);
// Just to save disk space, we delete the file because it is never needed again.