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build runner: fix single-threaded build #24830

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Merged
merged 1 commit into from
Aug 13, 2025
Merged

build runner: fix single-threaded build #24830

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32 changes: 18 additions & 14 deletions lib/compiler/build_runner.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -340,9 +340,10 @@ pub fn main() !void {
}
}

if (webui_listen != null and watch) fatal(
\\the build system does not yet support combining '--webui' and '--watch'; consider omitting '--watch' in favour of the web UI "Rebuild" button
, .{});
if (webui_listen != null) {
if (watch) fatal("using '--webui' and '--watch' together is not yet supported; consider omitting '--watch' in favour of the web UI \"Rebuild\" button", .{});
if (builtin.single_threaded) fatal("'--webui' is not yet supported on single-threaded hosts", .{});
}

const stderr: std.fs.File = .stderr();
const ttyconf = get_tty_conf(color, stderr);
Expand Down Expand Up @@ -449,16 +450,19 @@ pub fn main() !void {
try run.thread_pool.init(thread_pool_options);
defer run.thread_pool.deinit();

run.web_server = if (webui_listen) |listen_address| .init(.{
.gpa = gpa,
.thread_pool = &run.thread_pool,
.graph = &graph,
.all_steps = run.step_stack.keys(),
.ttyconf = run.ttyconf,
.root_prog_node = main_progress_node,
.watch = watch,
.listen_address = listen_address,
}) else null;
run.web_server = if (webui_listen) |listen_address| ws: {
if (builtin.single_threaded) unreachable; // `fatal` above
break :ws .init(.{
.gpa = gpa,
.thread_pool = &run.thread_pool,
.graph = &graph,
.all_steps = run.step_stack.keys(),
.ttyconf = run.ttyconf,
.root_prog_node = main_progress_node,
.watch = watch,
.listen_address = listen_address,
});
} else null;

if (run.web_server) |*ws| {
ws.start() catch |err| fatal("failed to start web server: {s}", .{@errorName(err)});
Expand Down Expand Up @@ -562,7 +566,7 @@ const Run = struct {
max_rss_mutex: std.Thread.Mutex,
skip_oom_steps: bool,
watch: bool,
web_server: ?WebServer,
web_server: if (!builtin.single_threaded) ?WebServer else ?noreturn,
/// Allocated into `gpa`.
memory_blocked_steps: std.ArrayListUnmanaged(*Step),
/// Allocated into `gpa`.
Expand Down
8 changes: 3 additions & 5 deletions lib/std/Build/WebServer.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -59,11 +59,9 @@ pub const Options = struct {
listen_address: std.net.Address,
};
pub fn init(opts: Options) WebServer {
if (builtin.single_threaded) {
// The upcoming `std.Io` interface should allow us to use `Io.async` and `Io.concurrent`
// instead of threads, so that the web server can function in single-threaded builds.
std.process.fatal("--webui not yet implemented for single-threaded builds", .{});
}
// The upcoming `std.Io` interface should allow us to use `Io.async` and `Io.concurrent`
// instead of threads, so that the web server can function in single-threaded builds.
comptime assert(!builtin.single_threaded);

const all_steps = opts.all_steps;

Expand Down