Xcode lldb debugging tips

Xcode_lldb_debug

Make sure Product->Scheme->Edit Scheme->Run is using "Debug" mode

(lldb) p NSPointFromString(@"{10.0, 20.0}");
error: 'NSPointFromString' has unknown return type; cast the call to its declared return type
error: 1 errors parsing expression
(lldb) p (NSPoint)NSPointFromString(@"{10.0, 20.0}”);
(NSPoint) $0 = (x = 10, y = 20)
(lldb) e @import UIKit
(lldb) po self.view.bounds

(lldb) p @import Foundation
(lldb) p NSPointFromString(@"{10.0, 20.0}");
(NSPoint) $1 = (x = 10, y = 20)

(lldb) fr v     //show arguments and local variables in current frame

(lldb) re r     //show general purpose registers for current thread

(lldb) di -f    //show disassemeble the current function for the current frame
...
0x10ff67f4e               ; symbol stub for: objc_msgSend
...
(lldb) b 0x10ff67f4e
(lldb) po $rsi 
4598742723
(lldb) x/s $rsi  //read memory as string
0x1121b3ec3: "viewControllerForKey:"

(lldb)memory read -f s $rsi //same as above

(lldb) memory read --size 8 --format x 0x7fff5b5fe5c8    //read memory with 8-byte chunck

(lldb) disassemble --start-address 0x0000000104601bd0    //disassemble from address

(lldb)s  //source level step in
(lldb)n  //source level step over

(lldb)si  //instruction level step in
(lldb)ni  //instruction level step over

(lldb)br s -n '-[HelperClass doThing:]' -K 0   //set breakpoint at the beginning of a method call (without skipping prologue)
(lldb)po [NSMethodSignature signatureWithObjCTypes:"c24@?0@8q16"] //get method signature object with objc method type encoding

(lldb)dis -n '-[HelperClass doThing:]'  //show disassembly for a method with its name. Very usefull when paired with 'br s -a'

(lldb)br s -a 0x10e2f5b10  //set breakpoint at an instruction with its address.
(lldb)br s -a `c-func` //set breakpoint at the beginning of a c function. cannot be used for objc method
(lldb)br s -a c-func  //same as above

(lldb)po [[NSNotificationCenter defaultCenter] debugDescription]  //debug notifications

(lldb)break set -r TIS|TSM.*  //regex breakpoint

(lldb) break command add 5   //add commands to breakpoint 5. The commands will be automatically executed when the breakpoint is hit.
Enter your debugger command(s).  Type 'DONE' to end.
> bt
> c
> DONE