pipe2

pub fn pipe2(flags: posix.O) PipeError![2]posix.fd_t {
    var fds: [2]posix.fd_t = undefined;

    if (@TypeOf(posix.system.pipe2) != void) {
        switch (posix.errno(posix.system.pipe2(&fds, flags))) {
            .SUCCESS => return fds,
            .INVAL => |err| return errnoBug(err), // Invalid flags
            .NFILE => return error.SystemFdQuotaExceeded,
            .MFILE => return error.ProcessFdQuotaExceeded,
            else => |err| return posix.unexpectedErrno(err),
        }
    }

    switch (posix.errno(posix.system.pipe(&fds))) {
        .SUCCESS => {},
        .NFILE => return error.SystemFdQuotaExceeded,
        .MFILE => return error.ProcessFdQuotaExceeded,
        else => |err| return posix.unexpectedErrno(err),
    }
    errdefer {
        closeFd(fds[0]);
        closeFd(fds[1]);
    }

    // https://github.com/ziglang/zig/issues/18882
    if (@as(u32, @bitCast(flags)) == 0) return fds;

    // CLOEXEC is special, it's a file descriptor flag and must be set using
    // F.SETFD.
    if (flags.CLOEXEC) for (fds) |fd| {
        switch (posix.errno(posix.system.fcntl(fd, posix.F.SETFD, @as(u32, posix.FD_CLOEXEC)))) {
            .SUCCESS => {},
            else => |err| return posix.unexpectedErrno(err),
        }
    };

    const new_flags: u32 = f: {
        var new_flags = flags;
        new_flags.CLOEXEC = false;
        break :f @bitCast(new_flags);
    };

    // Set every other flag affecting the file status using F.SETFL.
    if (new_flags != 0) for (fds) |fd| {
        switch (posix.errno(posix.system.fcntl(fd, posix.F.SETFL, new_flags))) {
            .SUCCESS => {},
            .INVAL => |err| return errnoBug(err),
            else => |err| return posix.unexpectedErrno(err),
        }
    };

    return fds;
}