How to print disassembly registers in the Xcode console - objective-c

Question

I'm looking at some disassembly code and see something like 0x01c8f09b <+0015> mov 0x8(%edx),%edi and I am wondering what the value of %edx or %edi is.
Is there a way to print the value of %edx or other assembly variables? Is there a way to print the value at the memory address that %edx points at (I'm assuming edx is a register containing a pointer to ... something here).
For example, you can print an objet by typing po in the console, so is there a command or syntax for printing registers/variables in the assembly?
Background:
I'm getting EXC_BAD_ACCESS on this line and I would like to debug what is going on. I'm aware this error is related to memory management and I'm looking at figuring out where I may be missing/too-many retain/release/autorelease calls.
Additional Info:
This is on IOS, and my application is running in the iPhone simulator.

Answer 1

You can print a register (e.g, eax) using:
print $eax
Or for short:
p $eax
To print it as hexadecimal:
p/x $eax
To display the value pointed to by a register:
x $eax
Check the gdb help for more details:
help print
help x

Answer 2

Depends up which Xcode compiler/debugger you are using. For gcc/gdb it's
info registers
but for clang/lldb it's
register read

Answer 3

(gdb) info reg
eax 0xe 14
ecx 0x2844e0 2639072
edx 0x285360 2642784
ebx 0x283ff4 2637812
esp 0xbffff350 0xbffff350
ebp 0xbffff368 0xbffff368
esi 0x0 0
edi 0x0 0
eip 0x80483f9 0x80483f9 <main+21>
eflags 0x246 [ PF ZF IF ]
cs 0x73 115
ss 0x7b 123
ds 0x7b 123
es 0x7b 123
fs 0x0 0
gs 0x33 51
From Debugging with gdb:
You can refer to machine register contents, in expressions, as variables with names
starting with `$'. The names of registers are different for each machine; use info
registers to see the names used on your machine.
info registers
Print the names and values of all registers except floating-point
registers (in the selected stack frame).
info all-registers
Print the names and values of all registers, including floating-point
registers.
info registers regname ...
Print the relativized value of each specified register regname.
regname may be any register name valid on the machine you are using,
with or without the initial `$'.

Answer 4

If you are using LLDB instead of GDB you can use register read

Answer 5

Those are not variables, but registers.
In GDB, you can see the values of standard registers by using the following command:
info registers
Note that a register contains integer values (32bits in your case, as the register name is prefixed by e). What it represent is not known. It can be a pointer, an integer, mostly anything.
If po crashes when you try to print a register's value as a pointer, it's likely that the value is not a pointer (or an invalid one).