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While trying to debug an AutoLayout problem (a table cell which should be growing according to the size of its content isn't, in some circumstances), I set a breakpoint on the last line of my tableView:heightForRow: method, and trying to print the value of systemLayoutSizeFittingSize: I get this:

(lldb) p ((CGSize)[cachedCell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize]).height
2014-10-14 11:15:49.492 AppName[72132:10302054] This NSLayoutConstraint is being configured with a constant that exceeds internal limits.  A smaller value will be substituted, but this problem should be fixed. Break on void _NSLayoutConstraintNumberExceedsLimit() to debug.  This will be logged only once.  This may break in the future.
(CGFloat) $0 = 57

Well ok, that's interesting. But I try and do what it says and set a breakpoint on that function:

Grab of breakpoint definition on _NSLayoutConstraintNumberExceedsLimit()

... and this breakpoint doesn't get hit.

  • Am I setting the breakpoint correctly?
  • In any case, any clues on what might be wrong with my constraints to lead to this?

(Annoyingly, it seems to work in some cases but not in others and I can't see a difference in the setup.)

Robert Atkins
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1 Answers1

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Omit the () from the symbol name. It's a little clearer what is happening if you use the debugger console window to set this breakpoint with the breakpoint set --name command:

(lldb) br s -n _NSLayoutConstraintNumberExceedsLimit()
Breakpoint 1: no locations (pending).
WARNING:  Unable to resolve breakpoint to any actual locations.
(lldb) br s -n _NSLayoutConstraintNumberExceedsLimit
Breakpoint 2: where = Foundation`_NSLayoutConstraintNumberExceedsLimit, address = 0x00007fff9168e6f5
(lldb)

If you had used the breakpoint list (br l) command in your Xcode debug session, you would have seen that the _NSLayoutConstraintNumberExceedsLimit() breakpoint didn't get set in any locations.

Jason Molenda
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  • Well, now I've got a breakpoint set according to `br l` (thank you!) but it still doesn't get hit—unless I call `p (CGSize)[cachedCell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize]` in the debugger, in which case I can see the hit count go up! – Robert Atkins Oct 15 '14 at 08:53
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    Finally solved the problem. If I have to set `preferredMaxLayoutWidth` on the label manually, what the hell is Auto Layout doing for me?! – Robert Atkins Oct 15 '14 at 14:30
  • @RobertAtkins, how did you fix it? – orkenstein Mar 31 '15 at 08:25
  • I had a label horizontally adjacent to a UIImageView in my cell. In order for the label to correctly calculate the height it wanted, I had to set its `preferredMaxLayoutWidth` to the width of the cell, minus the width of the UIImageView and any adjacent padding. That I had to do this at all I find kind of stupid, and it seems it's no longer necessary on iOS 8. – Robert Atkins Mar 31 '15 at 08:30
  • @RobertAtkins, looks really stupid. What in case of different cell width? – orkenstein Mar 31 '15 at 08:39
  • I think I subtracted the UIView & padding from the cell's contentView.frame.width? Don't have that code to hand right now. – Robert Atkins Mar 31 '15 at 08:58