objective c - Why no memory leak for: @property(copy) NSString* name, when I don't release it in dealloc? -

i turned arc off.

i have property in class declared this:

@property(copy) nsstring* name 

i set name constant string:

[greeter setname:@"jane"]; 

i implemented dealloc class this:

-(void)dealloc{     [super dealloc]; } 

i expected there memory leak because didn't release name. i'm using xcode 6.2 , product>analyze not identify leaks, , neither instruments: product>profile, choose leaks, hit red record button.

here relevant code:

// //  greeter.h //  flashlight2 //  #import <foundation/foundation.h>  @interface greeter : nsobject  @property(copy) nsstring* name;   -(nsstring*)description; -(void)dealloc;   @end 

....

// //  greeter.m //  flashlight2 //  #import "greeter.h"  @implementation greeter   -(nsstring*)description {     nsstring* msg = [[nsstring alloc] initwithstring:@"i greeter"];     return [msg autorelease]; }  -(void)dealloc{     [super dealloc]; }  @end 

...

@implementation appdelegate   - (bool)application:(uiapplication *)application didfinishlaunchingwithoptions:(nsdictionary *)launchoptions {      // override point customization after application launch.      greeter* greeter = [[greeter alloc] init];     [greeter setname:@"jane"];  //constant string in memory life of program      nslog(@"%@", greeter);     [greeter release];       return yes; } 

after thinking awhile, explanation can come name setter doesn't actually copy constant string. seems obj-c type check on the string being assigned property, , because it's constant string, obj-c assigns(?) the-pointer-to-the-constant-string name-pointer. going on?

there's 2 optimizations @ work here combine cause result.

first: nsstring literals stored in special segment of binary, rather allocated @ runtime. ignore retain , release, , never allocated or deallocated.

second: copying immutable nsstring (including string literal) instead retains it, because copy guaranteed identical original. (this accomplished overriding -retain , -release methods in private nsstring subclass)

so in scenario, copy turns retain, retain ignored, , deallocation wouldn't happen if did release string in dealloc.