No... you can't do that

Question

I remember one time getting chastised by my code or gcc or gdb saying I could not make a declaration inside a switch statement like this:
switch (a) {
NSString* str = @"";
case 1:
case 2:
Now I'm trying to do something similar as in:
if (a) {
NSString* str = @"";
[self dothis];
[self dothat];
And I don't get an outright error or warning, my code just goes off to never never land and eventually it comes back and gdb says:
Timed out fetching data. Variable display may be inaccurate.
I can't believe I've gone all these years and not tried to make a declaration inside an if statement. Maybe so, but it would surprise me.
Can anyone point me to the right docs to explain this?
Thanks.
-Phil

Answer 1

This generally means that some one of the "data formatters" is taking too long to return. You can verify this by turning OFF the data formatters with the Debug->Variables View->Enable Data Formatters menu item.
Some of the data types in Cocoa & Carbon - the string types & the collection types particularly - are opaque to the debugger, so to tell you their values we have to call some code in the program we are debugging. This can go wrong in numerous ways, most of which we intercept & deal with. But not all yet...
One common cause of problems is trying to run the data formatters on uninitialized objects. We don't actually have any way to tell for sure when an object is good or not. We have some heuristics, but stack objects sometimes point to the leftovers of another stack object that are "almost good enough" and fool us. One trick that will help out with this is when you are breaking in a function, break after the objects are initialized, not at the very beginning of the function.
Or, you can just leave the data formatters off, and use "po" or the "Print object" context-menu in the variable view to look at ObjC objects.