fix(tail): free dir-path alloc when a directory watch fails

src/tail/mod.zig

@@ -32,4 +32,6 @@ test {
     _ = @import("read_scheduler/common.zig");
     _ = @import("read_scheduler/poll.zig");
     _ = @import("watch_backend/poll.zig");
+    _ = @import("watch_backend/uring_linux.zig");
+    _ = @import("watch_backend/kqueue_macos.zig");
 }

src/tail/watch_backend/kqueue_macos.zig

@@ -154,7 +154,10 @@ fn ensureDirectoryWatch(kq: *State, path: []const u8) !void {
     errdefer kq.allocator.free(owned_dir_path);
 
     const dir = std.Io.Dir.cwd().openDir(kq.io, owned_dir_path, .{}) catch |err| switch (err) {
-        error.FileNotFound => return,
+        error.FileNotFound => {
+            kq.allocator.free(owned_dir_path);
+            return;
+        },
         else => return err,
     };
     const dir_fd = dir.handle;
@@ -170,6 +173,7 @@ fn ensureDirectoryWatch(kq: *State, path: []const u8) !void {
     }};
     if (kevent(kq.fd, changes[0..], &.{}, null) < 0) {
         closeFd(dir_fd);
+        kq.allocator.free(owned_dir_path);
         return;
     }
     try kq.dir_watches.append(kq.allocator, .{ .path = owned_dir_path, .fd = dir_fd });
@@ -198,3 +202,27 @@ fn markTrackedInDirDirty(self: anytype, dir_path: []const u8) void {
         }
     }
 }
+
+const testing = std.testing;
+
+test "ensureDirectoryWatch does not leak when parent directory is missing" {
+    if (comptime builtin.os.tag != .macos) return;
+    var kq = try init(std.testing.allocator, std.Options.debug_io);
+    defer deinit(&kq);
+
+    var tmp = testing.tmpDir(.{});
+    defer tmp.cleanup();
+    const root_abs = try tmp.dir.realPathFileAlloc(std.Options.debug_io, ".", testing.allocator);
+    defer testing.allocator.free(root_abs);
+    const target = try std.fmt.allocPrint(
+        testing.allocator,
+        "{s}/nonexistent_subdir_kqueue_leak/tail.log",
+        .{root_abs},
+    );
+    defer testing.allocator.free(target);
+
+    var i: usize = 0;
+    while (i < 50) : (i += 1) {
+        try ensureDirectoryWatch(&kq, target);
+    }
+}

src/tail/watch_backend/uring_linux.zig

@@ -171,7 +171,10 @@ fn ensureDirectoryWatch(u: *State, path: []const u8) !void {
     const owned_dir_path = try u.allocator.dupe(u8, dir_path);
     errdefer u.allocator.free(owned_dir_path);
 
-    const wd = inotifyAddWatch(u.fd, owned_dir_path, INOTIFY_MASK) catch return;
+    const wd = inotifyAddWatch(u.fd, owned_dir_path, INOTIFY_MASK) catch {
+        u.allocator.free(owned_dir_path);
+        return;
+    };
     errdefer inotifyRmWatch(u.fd, wd);
 
     try u.dir_path_to_wd.put(owned_dir_path, wd);
@@ -207,7 +210,7 @@ fn markTrackedInDirDirty(self: anytype, dir_path: []const u8) void {
 // inotify was removed from std.posix in Zig 0.16; wrap std.os.linux directly.
 fn inotifyInit1(flags: u32) !std.posix.fd_t {
     const rc = std.os.linux.inotify_init1(flags);
-    return switch (std.posix.errno(rc)) {
+    return switch (std.os.linux.errno(rc)) {
         .SUCCESS => @intCast(rc),
         .INVAL => error.InvalidArgument,
         .MFILE => error.ProcessFdQuotaExceeded,
@@ -220,7 +223,7 @@ fn inotifyInit1(flags: u32) !std.posix.fd_t {
 fn inotifyAddWatch(fd: std.posix.fd_t, path: []const u8, mask: u32) !i32 {
     const path_c = try std.posix.toPosixPath(path);
     const rc = std.os.linux.inotify_add_watch(fd, &path_c, mask);
-    return switch (std.posix.errno(rc)) {
+    return switch (std.os.linux.errno(rc)) {
         .SUCCESS => @intCast(rc),
         .ACCES => error.AccessDenied,
         .NOENT => error.FileNotFound,
@@ -234,3 +237,30 @@ fn inotifyAddWatch(fd: std.posix.fd_t, path: []const u8, mask: u32) !i32 {
 fn inotifyRmWatch(fd: std.posix.fd_t, wd: i32) void {
     _ = std.os.linux.inotify_rm_watch(fd, wd);
 }
+
+const testing = std.testing;
+
+test "ensureDirectoryWatch does not leak when parent directory is missing" {
+    if (comptime builtin.os.tag != .linux) return;
+    var u = init(std.testing.allocator, std.Options.debug_io) catch |err| switch (err) {
+        error.PermissionDenied, error.SystemOutdated => return error.SkipZigTest,
+        else => return err,
+    };
+    defer deinit(&u);
+
+    var tmp = testing.tmpDir(.{});
+    defer tmp.cleanup();
+    const root_abs = try tmp.dir.realPathFileAlloc(std.Options.debug_io, ".", testing.allocator);
+    defer testing.allocator.free(root_abs);
+    const target = try std.fmt.allocPrint(
+        testing.allocator,
+        "{s}/nonexistent_subdir_uring_leak/tail.log",
+        .{root_abs},
+    );
+    defer testing.allocator.free(target);
+
+    var i: usize = 0;
+    while (i < 50) : (i += 1) {
+        try ensureDirectoryWatch(&u, target);
+    }
+}