OK, so here are the details on remote debugging; I’ve finished this phase of XRay 2 development and will in the next few weeks be fully available for pressing on with it.

The basic idea is that I have only PowerPC Macs, and since nobody I know in Brazil has received an Intel Mac (except for a couple of DTKs, which I didn’t want to use), the solution was to use Xcode‘s remote debugging capabilites, running my executable at a machine in the ADC Compatibility Labs. These are open at no extra charge to paying developers, but most of what I’ll detail would apply to any other machine.

Most of it is explained in the Xcode User Guide. Note that I used Xcode 2.2.1, but I think this facility has been available at least since 2.0. Click on the “Remote Debugging in Xcode” section in the left frame. First, however, send e-mail to adc.labs(at)mail.apple.com and ask for machine time, explaining for how long you need the machine; I asked for 3 days (thanks, Joe Holmes!). Basically, they’ll set up a newly formatted Mac with everything standard installed, including the latest developer tools. You should check that you have the same version, I suppose. They’ll have ssh and Apple Remote Desktop activated, and will send you the IP address, usercode and password. For illustration, let’s say the IP number is 10.1.1.1 (NOT an actual IP!), the usercode is “adclabs” and the password is “stevejobs”; substitute the actual values as appropriate.

In other words, all you’ll do there will be inside the default home folder “adclabs”. This user is also an administrator, so you’ll be able to use the password whenever needed for that. If you have a second Mac handy, you could rehearse first with that, of course; it’s what I did, as I’m normally not that handy with the Terminal. (Thanks, by the way, to John C. Randolph, Mike Ash and several others for helping me with details.)

First step is to generate a public and private key pair; you can skip this if you already have done so in the past. Open Terminal and type:

ls ~/.ssh/

If it lists a few files, among them one called “id_rsa.pub”, you already have a key pair. If not, type:

ssh-keygen -b 2048 -t dsa

This will take about a minute and then prompt you for a file path; type <return> to use the default path. It will then prompt you for a passphrase, twice. Don’t leave this empty and don’t use too short a phrase. You now should have the id_rsa.pub file in the ~/.ssh directory.

Second step is to open Terminal and type:

ssh adclabs@10.1.1.1

wait for the Password: prompt and type in “stevejobs”, or whatever password they sent you. You should see the normal Terminal prompt now, with a name like “CE-Lab-ADC-Compatibility-Labs-Intel-iMac” at the start of the line.

Now you’d better change the password to the same passphrase you used for the RSA key – yes, usually it’s recommended to use different passwords here, but that way you won’t have to remember which one to use where; it’s just for a couple of days, anyway. Type

passwd

and you’ll be prompted for the original password, then twice for the new password. Create a .ssh directory with

mkdir ~/.ssh

and log out by typing

exit

Next step is to transfer the public key to the remote Mac. To do this, at your local prompt, type

scp ~/.ssh/id_rsa.pub adclabs@10.1.1.1:~/.ssh/authorized_keys

it will ask for your password again, and transfer the file over. Now log in again with:

ssh adclabs@10.1.1.1

and if all is well, it won’t ask for your passphrase or password again, but just log in. Now restrict permissions on your key by typing

chmod go-rwx ~/.ssh/authorized_keys

Now you need to set up a local build folder. The trick here is that both machines should see your build folder at the same absolute path. There are several ways to achieve that; on a local network, you could have one of the machines serve the entire folder to the other, then use symbolic links to map the same path. However, I found that over a long distance it’s most efficient to have mirrored folders at both machines, and copy the contents over with an extra build phase. Here’s what I did.

At the remote machine, type

mkdir ~/build

which will create an empty build folder in the Home folder. Log out and close Terminal.

Now, on your local machine, you need to prep Xcode for what you’ll do. Double-click on your main project group and go to the “General” tab. Click “Place Build Products In: Custom location” and type in “/Users/adclabs/build” as the location. (Supposing, of course, that you don’t have a user called “adclabs”…)

Also check “Place Intermediate Build Ïiles In: Default intermediates location”, which probably will already be checked. Now click on your target and, from the Project menu, select “New Run Script Build Phase”. Make sure the new build phase is the last one, and enter this line as the script:

rsync -rz /Users/adclabs/build adclabs@10.1.1.1:/Users/adclabs

Finally, double-click on your executable in Xcode, and in the “Debugging” tab, select “Use Pipe for standard input/output”, check “Debug executable remotely via SSH”, and in the “Connect to:” field, type

adclabs@10.1.1.1

Now you’re ready. You’ll notice a delay of a few minutes while the last build phase transfers the files over, and on the start of a debugging run there’ll be several errors logged to the debug console, but eventually you’ll be debugging and single-stepping as usual, albeit more slowly. For GUI debugging, of course, you’ll have to use Apple Remote Desktop; I wish Apple would include a 1-user license for this in the Select package, as it’s rather expensive…

Have fun! I’ve tried to double-check most of this as I typed it in, please tell me if something didn’t work.

Update: fixed a typing error.