How to get parameters using symbolic breakpoints in Objective-C

objective-c xcode debugging lldb
Dan Rosenstark picture Dan Rosenstark · Mar 20, 2013 · Viewed 9.4k times · Source

I have a breakpoint that looks like this

-[UITableViewCell setSelected:]

and it works, but I cannot figure out how to get the value that is being passed in.

I have tried -[UITableViewCell setSelected:(BOOL)what] and -[UITableViewCell setSelected:what] which do not work at all.

How can I access the parameters?

If this doesn't work, I'll have to make a DebugUITableViewCell just to see what's going on, which is a hassle and touches a lot of code.

Answer

Aaron Golden picture Aaron Golden · Mar 20, 2013

If you debug your code on the device the parameters when you hit your breakpoint will consistently be in registers r0, r1, and r2. If you use po $r0 you'll see the object receiving setSelected. If you use po $r1 you'll get "no Objective-C description available" because that's the selector. Inspect $r2 to see if selected is being set to YES or NO. It's a similar story on i386, but I can't remember off hand which registers are used.

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