OpenEuphoria

The problem here is that buffer_multi is an empty sequence. After making your change and running interpreted, I get:

 foo1.ex <new file> 
function 
/home/matt/eu/oe/hg/bin/ed.ex:2035 in procedure insert_string() 
subscript value 1 is out of bounds, reading from a sequence of length 0 - in subscript #1 of 'buffer_multi'  

I don't know enough about the guts of ed.ex to know what this means, but an error like that would slip through translated code to give you the sort of malloc error that Tom is reporting.