Zig 0.16 Compatibility

This makes libxev work with Zig 0.16.

**Fair warning that this is messy.** The goal was to keep libxev working
with minimal external API changes. That means we don't play nicely with
`std.Io` yet and I'm not 100% sure what the path forward is for that since
in many ways libxev is an alternate implementation but std.Io doesn't have
full coverage for our functionality so we can't simply switch to it
either.

In cases wher we need an Io here, I use the global single threaded Io
which preserves the Zig 0.15 behavior. Like I said, the goal is to get
people who use libxev (including me) upgraded to 0.16, not to fully
adapt to the new idioms.

Particularly nasty is the large amount of shims we need in `src/posix.zig`
and `src/windows.zig` to address removed APIs from Zig.

Author: mitchellh

.github/workflows/test.yml

@@ -1,7 +1,7 @@
 on: [push, pull_request]
 name: Test
 env:
-  ZIG_VERSION: 0.15.2
+  ZIG_VERSION: 0.16.0
 
 jobs:
   build:

README.md

@@ -272,7 +272,7 @@ directory.
 
 # Build
 
-Build requires the installation of the Zig 0.15.1. libxev follows stable
+Build requires the installation of the Zig 0.16. libxev follows stable
 Zig releases and generally does not support nightly builds. When a stable
 release is imminent we may have a branch that supports it.
 **libxev has no other build dependencies.**

build.zig

@@ -26,7 +26,6 @@ pub fn build(b: *std.Build) !void {
         true
     else |err| switch (err) {
         error.FileNotFound => false,
-        else => return err,
     };
 
     const emit_bench = b.option(
@@ -41,25 +40,23 @@ pub fn build(b: *std.Build) !void {
         "Install the example binaries to zig-out",
     ) orelse false;
 
-    const c_api_module = b.createModule(.{
-        .root_source_file = b.path("src/c_api.zig"),
-        .target = target,
-        .optimize = optimize,
-    });
-
     // Static C lib
     const static_lib: ?*Step.Compile = lib: {
         if (target.result.os.tag == .wasi) break :lib null;
 
         const static_lib = b.addLibrary(.{
             .linkage = .static,
             .name = "xev",
-            .root_module = c_api_module,
+            .root_module = b.createModule(.{
+                .root_source_file = b.path("src/c_api.zig"),
+                .target = target,
+                .optimize = optimize,
+                .link_libc = true,
+            }),
         });
-        static_lib.linkLibC();
         if (target.result.os.tag == .windows) {
-            static_lib.linkSystemLibrary("ws2_32");
-            static_lib.linkSystemLibrary("mswsock");
+            static_lib.root_module.linkSystemLibrary("ws2_32", .{});
+            static_lib.root_module.linkSystemLibrary("mswsock", .{});
         }
         break :lib static_lib;
     };
@@ -72,7 +69,11 @@ pub fn build(b: *std.Build) !void {
         const dynamic_lib = b.addLibrary(.{
             .linkage = .dynamic,
             .name = "xev",
-            .root_module = c_api_module,
+            .root_module = b.createModule(.{
+                .root_source_file = b.path("src/c_api.zig"),
+                .target = target,
+                .optimize = optimize,
+            }),
         });
         break :lib dynamic_lib;
     };
@@ -119,20 +120,19 @@ pub fn build(b: *std.Build) !void {
             "test-filter",
             "Filter for test",
         );
-        const test_exe = b.addTest(.{
+        break :test_exe b.addTest(.{
             .name = "xev-test",
             .filters = if (test_filter) |filter| &.{filter} else &.{},
             .root_module = b.createModule(.{
                 .root_source_file = b.path("src/main.zig"),
                 .target = target,
                 .optimize = optimize,
+                .link_libc = switch (target.result.os.tag) {
+                    .linux, .macos => true,
+                    else => null,
+                },
             }),
         });
-        switch (target.result.os.tag) {
-            .linux, .macos => test_exe.linkLibC(),
-            else => {},
-        }
-        break :test_exe test_exe;
     };
 
     // "test" Step
@@ -172,19 +172,24 @@ fn buildBenchmarks(
     b: *std.Build,
     target: std.Build.ResolvedTarget,
 ) ![]const *Step.Compile {
+    const io = b.graph.io;
     const alloc = b.allocator;
     var steps: std.ArrayList(*Step.Compile) = .empty;
     defer steps.deinit(alloc);
 
-    var dir = try std.fs.cwd().openDir(try b.build_root.join(
-        b.allocator,
-        &.{ "src", "bench" },
-    ), .{ .iterate = true });
-    defer dir.close();
+    var dir = try std.Io.Dir.cwd().openDir(
+        io,
+        try b.build_root.join(
+            b.allocator,
+            &.{ "src", "bench" },
+        ),
+        .{ .iterate = true },
+    );
+    defer dir.close(io);
 
     // Go through and add each as a step
     var it = dir.iterate();
-    while (try it.next()) |entry| {
+    while (try it.next(io)) |entry| {
         // Get the index of the last '.' so we can strip the extension.
         const index = std.mem.lastIndexOfScalar(
             u8,
@@ -223,19 +228,24 @@ fn buildExamples(
     optimize: std.builtin.OptimizeMode,
     c_lib_: ?*Step.Compile,
 ) ![]const *Step.Compile {
+    const io = b.graph.io;
     const alloc = b.allocator;
     var steps: std.ArrayList(*Step.Compile) = .empty;
     defer steps.deinit(alloc);
 
-    var dir = try std.fs.cwd().openDir(try b.build_root.join(
-        b.allocator,
-        &.{"examples"},
-    ), .{ .iterate = true });
-    defer dir.close();
+    var dir = try std.Io.Dir.cwd().openDir(
+        io,
+        try b.build_root.join(
+            b.allocator,
+            &.{"examples"},
+        ),
+        .{ .iterate = true },
+    );
+    defer dir.close(io);
 
     // Go through and add each as a step
     var it = dir.iterate();
-    while (try it.next()) |entry| {
+    while (try it.next(io)) |entry| {
         // Get the index of the last '.' so we can strip the extension.
         const index = std.mem.lastIndexOfScalar(
             u8,
@@ -269,11 +279,11 @@ fn buildExamples(
                 .root_module = b.createModule(.{
                     .target = target,
                     .optimize = optimize,
+                    .link_libc = true,
                 }),
             });
-            exe.linkLibC();
-            exe.addIncludePath(b.path("include"));
-            exe.addCSourceFile(.{
+            exe.root_module.addIncludePath(b.path("include"));
+            exe.root_module.addCSourceFile(.{
                 .file = b.path(b.fmt(
                     "examples/{s}",
                     .{entry.name},
@@ -286,7 +296,7 @@ fn buildExamples(
                     "-D_POSIX_C_SOURCE=199309L",
                 },
             });
-            exe.linkLibrary(c_lib);
+            exe.root_module.linkLibrary(c_lib);
             break :exe exe;
         };
 
@@ -298,18 +308,20 @@ fn buildExamples(
 }
 
 fn manPages(b: *std.Build) ![]const *Step {
+    const io = b.graph.io;
     const alloc = b.allocator;
     var steps: std.ArrayList(*Step) = .empty;
     defer steps.deinit(alloc);
 
-    var dir = try std.fs.cwd().openDir(try b.build_root.join(
-        b.allocator,
-        &.{"docs"},
-    ), .{ .iterate = true });
-    defer dir.close();
+    var dir = try std.Io.Dir.cwd().openDir(
+        io,
+        try b.build_root.join(b.allocator, &.{"docs"}),
+        .{ .iterate = true },
+    );
+    defer dir.close(io);
 
     var it = dir.iterate();
-    while (try it.next()) |*entry| {
+    while (try it.next(io)) |*entry| {
         // Filenames must end in "{section}.scd" and sections are
         // single numerals.
         const base = entry.name[0 .. entry.name.len - 4];
@@ -321,7 +333,7 @@ fn manPages(b: *std.Build) ![]const *Step {
         ) });
 
         try steps.append(alloc, &b.addInstallFile(
-            cmd.captureStdOut(),
+            cmd.captureStdOut(.{}),
             b.fmt("share/man/man{s}/{s}", .{ section, base }),
         ).step);
     }

build.zig.zon

@@ -1,6 +1,6 @@
 .{
     .name = .libxev,
-    .minimum_zig_version = "0.15.1",
+    .minimum_zig_version = "0.16.0",
     .version = "0.0.0",
     .fingerprint = 0x30f7363573edabf3,
     .paths = .{""},

examples/_basic.zig

@@ -1,5 +1,4 @@
 const std = @import("std");
-const Instant = std.time.Instant;
 const xev = @import("xev");
 
 pub fn main() !void {

flake.lock

@@ -23,7 +23,7 @@
       # Other overlays
       (final: prev: rec {
         zigpkgs = inputs.zig.packages.${prev.system};
-        zig = inputs.zig.packages.${prev.system}."0.15.2";
+        zig = inputs.zig.packages.${prev.system}."0.16.0";
 
         # Our package
         libxev = prev.callPackage ./nix/package.nix {};

flake.nix

@@ -39,6 +39,12 @@ const ThreadPool = @This();
 const std = @import("std");
 const assert = std.debug.assert;
 const Atomic = std.atomic.Value;
+const Io = std.Io;
+
+// I know we shouldn't use a global io here, but we are doing this
+// during the transition period so libxev is at least usable with Zig
+// 0.16 until we do a cleaner transition.
+const io = Io.Threaded.global_single_threaded.io();
 
 stack_size: u32,
 max_threads: u32,
@@ -487,7 +493,7 @@ const Event = struct {
             // Acquiring to WAITING will make the next notify() or shutdown() wake a sleeping futex thread
             // who will either exit on SHUTDOWN or acquire with WAITING again, ensuring all threads are awoken.
             // This unfortunately results in the last notify() or shutdown() doing an extra futex wake but that's fine.
-            std.Thread.Futex.wait(&self.state, WAITING);
+            io.futexWaitUncancelable(u32, &self.state.raw, WAITING);
             state = self.state.load(.monotonic);
             acquire_with = WAITING;
         }
@@ -513,7 +519,7 @@ const Event = struct {
         // Only wake threads sleeping in futex if the state is WAITING.
         // Avoids unnecessary wake ups.
         if (state == WAITING) {
-            std.Thread.Futex.wake(&self.state, wake_threads);
+            io.futexWake(u32, &self.state.raw, wake_threads);
         }
     }
 };

src/ThreadPool.zig

@@ -65,6 +65,9 @@ pub fn Xev(comptime be: Backend, comptime T: type) type {
         pub const TCP = @import("watcher/tcp.zig").TCP(Self);
         pub const UDP = @import("watcher/udp.zig").UDP(Self);
 
+        /// Networking types shared across watchers.
+        pub const net = @import("posix.zig").net;
+
         /// The callback of the main Loop operations. Higher level interfaces may
         /// use a different callback mechanism.
         pub const Callback = loop.Callback(T);