"This NSLayoutConstraint is being configured with a constant that exceeds internal limits"

Question

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:

... 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.)

Solution

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.

Comments

[Robert Atkins]

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]

Finally solved the problem. If I have to set preferredMaxLayoutWidth on the label manually, what the hell is Auto Layout doing for me?!

[orkenstein]

@RobertAtkins, how did you fix it?

[Robert Atkins]

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.

[orkenstein]

@RobertAtkins, looks really stupid. What in case of different cell width?

[Robert Atkins]

I think I subtracted the UIView & padding from the cell's contentView.frame.width? Don't have that code to hand right now.

[Dani]

What is "0x00007fff9168e6f5"?

[John Stephen]

@DanielSpringer 0x00007fff9168e6f5 is the memory address of the function _NSLayoutConstraintNumberExceedsLimit, but it can/will change each run so you have to use the symbol _NSLayoutConstraintNumberExceedsLimit.