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1. Breaking on a stripped binary with no main function

   (gdb) inf files
   Symbols from "/private/tmp/hello".
   Mac OS X executable:
       /private/tmp/hello, file type mach-o-le.
       Entry point: 0x000000f4
       0x00000000 - 0x00000042 is LC_SEGMENT.__TEXT in /private/tmp/hello
       0x000000e8 - 0x00000128 is LC_SEGMENT.__TEXT.__text in /private/tmp/hello
   

2. Debugging Objective-C

   (gdb) break setPassword:
   (gdb) break -[Person setPassword:]
   
   (gdb) po self
   <Person: 0x10010c7a0>
   (gdb) po [invocation debugDescription]
   Some day, NSInvocation will have a useful debug
   (gdb) p (char *)_cmd
   $1 = 0x10fbb "setPassword:"
   
   (gdb) frame
   (gdb) info locals
   (gdb) info (classes|selectors) [regex]
   (gdb) list +[Person string]
   (gdb) call [self setPassword:@"welcome"]
   
   (gdb) where
   #0  0x0000b4b3 in -[AppDelegate application:didFinishLaunchingWithOptions:] (...)
   #1  0x00444c89 in -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] ()
   #2  0x00446d88 in -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] ()'),
   

3. Get a stack trace of all threads

   (gdb) thread apply all where
   

4. Inspect Objective-C methods parameters

   (gdb) info args
   self = (AppController *) 0x12b9f0
   _cmd = (SEL) 0x12f33
   aNotification = (NSNotification *) 0x264a320
   

   i386 - on the stack

   (int *)($ebp+8)     self
   (int *)($ebp+12)    cmd
   (int *)($ebp+16)    arg2
   (int *)($ebp+20)    arg3
   (int *)($ebp+24)    arg4
   (int *)($ebp+28)    arg5
   
   (int *)$eax         return address
   

   ex: (gdb) po *(int*)($ebp+8)

   i386 - in registers

   $esi       self
   $edx       cmd
   $ecx       arg2
   

   x86_64 - in registers

   $rdi          self
   $rsi          cmd
   $rdx          arg2
   $rcx          arg3
   $r8           arg4
   $r9           arg5
   
   $rax          return address
   

   ex: (gdb) po $rax