Unreachable code when printing help menu

[mitchelldw01]

I ran across a bug (user error?) where the program panics with an unreachable code error when trying to print help text. It occurs specifically when trying to use an array option on a subcommand. Here is a minimal example that produces the error:

const std = @import("std");
const cli = @import("zig-cli");

const heap = std.heap;

var gpa = std.heap.GeneralPurposeAllocator(.{}){};
const allocator = gpa.allocator();

pub fn main() !void {
    const action = try parseArgs();
    return action();
}

fn parseArgs() cli.AppRunner.Error!cli.ExecFn {
    var r = try cli.AppRunner.init(heap.page_allocator);

    const app = cli.App{
        .command = cli.Command{
            .name = "demo",
            .description = cli.Description{
                .one_line = "Demo app",
            },
            .target = cli.CommandTarget{
                .subcommands = &.{
                    try devCommand(&r),
                },
            },
        },
    };

    return r.getAction(&app);
}

var dev_context = struct {
    attach: []const []const u8 = undefined,
}{};

fn devCommand(r: *cli.AppRunner) !cli.Command {
    return cli.Command{
        .name = "dev",
        .options = &.{
            .{
                .long_name = "attach",
                .short_alias = 'a',
                .help = "Attach to service output",
                .value_ref = r.mkRef(&dev_context.attach),
            },
        },
        .target = cli.CommandTarget{
            .action = cli.CommandAction{
                .exec = execDevCommand,
            },
        },
    };
}

fn execDevCommand() !void {
    std.debug.print("Not implemented.\n", .{});
}

I can then cause the error by running zig build run -- dev --help.

I'm using Zig version 0.13.0-dev.266+0b0625ccf, but this occurs on version 0.12.0 as well.

I'm using the latest zig-cli version from this commit 9a94c4803a52e54c26b198096d63fb5bde752da2.

[sam701]

@mitchelldw01 Thanks for reporting. I can reproduce this issue. It happens when you call with zig build run -- .... It's working when you call ./zig-out/bin/dev --help. I will look into.

[sam701]

The error does not happen if there is no zig-cache and zig-out directories. The error happens only on the second run when the folders already present.

Here is the error

thread 136939 panic: reached unreachable code
/Users/alexei/opt/zig/lib/std/debug.zig:403:14: 0x102cca337 in assert (build)
    if (!ok) unreachable; // assertion failure
             ^
/Users/alexei/opt/zig/lib/std/Build/Cache.zig:896:15: 0x102e0f8c3 in writeManifest (build)
        assert(self.have_exclusive_lock);
              ^
/Users/alexei/opt/zig/lib/std/Build/Step.zig:554:26: 0x102e10233 in writeManifest (build)
        man.writeManifest() catch |err| {
                         ^
/Users/alexei/opt/zig/lib/std/Build/Step/Run.zig:713:31: 0x102db120b in make (build)
        try step.writeManifest(&man);
                              ^
/Users/alexei/opt/zig/lib/std/Build/Step.zig:182:13: 0x102d4165b in make (build)
    s.makeFn(s, prog_node) catch |err| switch (err) {
            ^
/Users/alexei/opt/zig/lib/compiler/build_runner.zig:948:31: 0x102d06c8f in workerMakeOneStep (build)
    const make_result = s.make(&sub_prog_node);
                              ^
/Users/alexei/opt/zig/lib/std/Thread/Pool.zig:102:39: 0x102d075fb in runFn (build)
            @call(.auto, func, closure.arguments);
                                      ^
/Users/alexei/opt/zig/lib/std/Thread/Pool.zig:191:18: 0x102d6b977 in worker (build)
            runFn(&run_node.data);
                 ^
/Users/alexei/opt/zig/lib/std/Thread.zig:408:13: 0x102d3fea7 in callFn__anon_14051 (build)
            @call(.auto, f, args);
            ^
/Users/alexei/opt/zig/lib/std/Thread.zig:674:30: 0x102d064a7 in entryFn (build)
                return callFn(f, args_ptr.*);
                             ^
???:?:?: 0x19b2a6f93 in ??? (libsystem_pthread.dylib)
???:?:?: 0x957b00019b2a1d33 in ??? (???)

It can be also a bug in the zig build system. This issue in zig https://github.com/ziglang/zig/issues/19973 seems to be related.

[sam701]

@mitchelldw01 I cannot reproduce this error any more with zig-master. I'm going to close this issue. But I can reopen if it's not the case for you.