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Bug introduced in 9.0 or earlier, persisting through 13.2 or later


With the following Dynamic cell, I can reproducibly crash Mathematica, so do not try this unless you have saved all your work!

l=1;
Dynamic[Sin[l = l + 1]]

This will harmlessly run forever, or until you try to right-click on the dynamic output (to get the context menu and perhaps to copy the current value). When you right-click on it, Mathematica crashes.

Is there a simple way to avoid or catch this error before it occurs?

Edit

I also see this crash when literally using the example from the documentation for Dynamic (under "Applications"):

{Trigger[Dynamic[x, (a = FractionalPart[#]; x = Round[#]) &], {0, 
   Infinity}], 
 Dynamic[{Quotient[x, 60], Mod[x, 60], SetPrecision[10 a, 2]}]}

and again trying to right-click. So it's not like I'm doing something outlandish here.

Edit 2 The link Szabolcs found does indeed answer my question:

EventHandler[Dynamic[Sin[l = l + 1]], {"MouseUp", 2} :> Null]

seems to prevent the crash.

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  • $\begingroup$ You should definitely report the crash to WRI. $\endgroup$
    – Szabolcs
    Feb 19, 2012 at 19:22
  • $\begingroup$ You'll be interested in this: groups.google.com/d/topic/comp.soft-sys.math.mathematica/… $\endgroup$
    – Szabolcs
    Feb 19, 2012 at 19:35
  • $\begingroup$ @Szabolcs Thanks, that must be the same error, and the fix works. Do you want to post this as an answer? $\endgroup$
    – Jens
    Feb 19, 2012 at 19:41
  • $\begingroup$ I can't reproduce it on V9. I'll try later on 9.0.1.0. $\endgroup$
    – Kuba
    Mar 25, 2014 at 16:45
  • $\begingroup$ @Kuba, yes, I think this was fixed in the meantime - I don't see the crash on 9.0.1 anymore. But in your question here, the fix seems to work. $\endgroup$
    – Jens
    Mar 25, 2014 at 16:49

1 Answer 1

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Based on this MathGroup post describing a similar crash, the right click can be caught and discarded like this:

l = 1;
EventHandler[Dynamic[Sin[l = l + 1]], {"MouseUp", 2} :> Null]

This won't let you copy the value, but it will prevent crashes due to accidental right clicks.

You can obtain the value by evaluating l as a different input.

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