I installed XCode but cannot find the executable. Where does it get installed?

Once you download and install XCode, the executable can be found here:

Macintosh HD > Developer > Applications > XCode

Debugging "objc[17695]: FREED(id): message release sent to freed object=0x1073d0"

Here's a good article on how to troubleshoot these kinds of errors:
http://www.cocoadev.com/index.pl?DebuggingAutorelease

Taken from the article:

One of the most opaque bugs I've had to deal with in Cocoa is leaving a released object in the autorelease pool, causing an EXC_BAD_ACCESS in NSPopAutoreleasePool?(). When this happens, it's pretty much impossible to tell what the doubly-released object was and where it was instantiated.

Fear no more! Using Cocoa's NSZombie? debugging class and the command-line malloc_history tool, we can nail this bug in a pinch.

Suppose you have the following (obviously incorrect) code:

  NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
 NSData* data = [NSData dataWithBytes:"asklaskdxjgr" length:12];

 [data release];
 [pool release];

The dataWithBytes: method sends an autorelease message to the created object, so we don't need to release it ourselves. When the autorelease pool is tossed the freed data object gets another release message, our app crashes, and we have no idea why.

The dataWithBytes: method sends an autorelease message to the created object, so we don't need to release it ourselves. When the autorelease pool is tossed the freed data object gets another release message, our app crashes, and we have no idea why.

Here's what we do:

Click on the "Targets" tab, open "Executables" and select the app (In XCode 2.0, double-click the executable in the file tree and select the arguments tab to enter environment variables). In the executable settings, add the following environment variables and set their values to "YES" (without the quotes):

  NSDebugEnabled
NSZombieEnabled
MallocStackLogging

You may also want the following environment variable set to YES:

  MallocStackLoggingNoCompact

With NSZombieEnabled, Cocoa sets an object's isa pointer to the NSZombie? class when its retain count drops to zero instead of deallocating it. Then when you send a message to an NSZombie? object (i.e., you're accessing freed data), it raises an exception and tells you where the object lives:

  2003-03-18 13:01:38.644 autoreleasebug[3939] *** *** Selector 'release'
sent to dealloced instance 0xa4e10 of class NSConcreteData.

Since you have MallocStackLogging turned on, you can now run "malloc_history

" to see the stack trace when the object was allocated:

  [dave@host193 Frameworks]$ malloc_history 3939 0xa4e10

Call [2] [arg=32]: thread_a0000dec |0x1000 | start | _start | main |
+[NSData dataWithBytes:length:] | NSAllocateObject | object_getIndexedIvars |
malloc_zone_calloc 

if you run under gdb, you may enter:

 (gdb) shell malloc_history 3939 0xa4e10

And there it is: the double-released object was allocated with [NSData dataWithBytes:length:] in the function main()!

I love you, Cocoa!