141 child run nonzero exit stderr term

// Pins that a child run with nonzero exit surfaces stderr through the
// | failed arm: the proc returns result.term.Exited as code and a duped copy
// of stderr as msg. (The 2026-07-02 pin was a Term union-tag corruption that
// no longer reproduces; the residual crash was this proc returning a slice
// its own defer freed — a source-level use-after-free, identical in raw Zig.
// msg must be duped because the defers below release Child.run's buffers.)

~import std/io
const std = @import("std");

~tor run-cmd { argv0: string }
| ok i32
| failed { code: i32, msg: string }

~proc run-cmd|zig {
    const allocator = std.heap.page_allocator;
    const result = std.process.Child.run(.{
        .allocator = allocator,
        .argv = &[_][]const u8{ argv0, "-c", "printf 'error message to stderr' 1>&2; exit 3" },
    }) catch |err| {
        return .{ .failed = .{ .code = -1, .msg = @errorName(err) } };
    };
    defer allocator.free(result.stdout);
    defer allocator.free(result.stderr);

    if (result.term.Exited != 0) {
        const msg = allocator.dupe(u8, result.stderr) catch {
            return .{ .failed = .{ .code = @intCast(result.term.Exited), .msg = "stderr dupe failed" } };
        };
        return .{ .failed = .{ .code = @intCast(result.term.Exited), .msg = msg } };
    }
    return .{ .ok = 0 };
}

~run-cmd(argv0: "sh")
| ok _ |> std/io:print.ln("ok")
| failed e |> std/io:print.ln(e.msg)