Debugging iOS signal exceptions in iOS private code

Question

I know quite a title.

However I seem to keep getting these mysterious errors & all GDB shows me is the line number of Apples code thats gone bang. I.e.

0x028235bd  <+0025>  jne    0x28235dd <_ZN2CA5Layer15collect_layers_EPNS0_17CollectLayersDataE+57>
0x028235bf  <+0027>  mov    0x4(%eax),%ecx
0x028235c2  <+0030>  test   %ecx,%ecx
0x028235c4  <+0032>  js     0x28235dd <_ZN2CA5Layer15collect_layers_EPNS0_17CollectLayersDataE+57>
0x028235c6  <+0034>  mov    0x8(%ebp),%edx
0x028235c9  <+0037>  mov    0x78(%edx,%ecx,4),%edx          <---- EXC_BAD_ACCESS

I just want to iterate that the above I know indicates that a released object is being accessed again. However the issue is how do I debug this when I don't have a stacktrace or even the register values?

Its not just EXC_BAD_ACCESS but also SIGABRT errors otherwise I could use the NSZombieEnabled trick.

(As a further note, this call trace is related to ViewControllers and the like, so any pointers debugging these would be helpful too)

Thanks again.

Answer 1

Open the xCode, press command+6, tap the '+' button at the bottom, select Add Exception Breakpoint, press done. Now if any exception is being thrown, the xCode will highlight the line of code that threw it.