How to find what is causing a closure allocation

[John Colvin]

I have a function that allocates a closure somewhere in it (as 
shown by the result of -profile=gc).

I can't make the function nogc as it calls a lot of other GC 
using code.

profilegc.log only gives me the line number of the function 
signature, which doesn't give me any hint as to where in the 
function the closure is allocated.

Anyone have any nice tricks to help narrow this down.