lldb command if statement - if-statement

Question

Hi I need to write a lldb breakpoint command that evaluates a value and prints out a value.
In gdb I could do it like this:
if ($value==2)
printf "Value is 2\n"
end
But in lldb the 'if-statement' is invalid it seems:
failed with error: 'if' is not a valid command.
error: Unrecognized command 'if'.
Can anyone tell me how to write this comparison inside my breakpoint command? Thanks!

Answer 1

You can use the expression parser to achieve this effect in some cases, and you can use the lldb Python interpreter for whatever complex work you want to do in response to a breakpoint hit. Given the fairly deep level of Python support, we felt if you don't know Python, you time would be better spent learning a little bit of that so you could really script lldb, rather than learning whatever little micro-language we would come up with.
Anyway, so using the interpreter, you could for instance do:
expr if ($value == 2) { (int) printf("Value is 2\n"); }
And using the python interpreter you can write a callback like:
def myCallback (frame, breakpoint_location, dict):
value = frame.FindValue("$value", lldb.eValueTypeConstResult)
if (value.unsigned == 10):
print "Value is 10"
put that in a file called myModule.py, do:
(lldb) command script import myModule.py
and then assign the command to your breakpoint with:
(lldb) breakpoint command add -F myModule.myCallback <BREAKPOINT_NUMBER>
That python example was a little more complex than normal because you were looking up lldb's equivalent of gdb's "convenience variable". If you were looking up a local, you could use frame.FindVariable.
More details on this at:
http://lldb.llvm.org/python-reference.html