make_arrow in arrow.c in Xfig fig2dev 3.2.7b allows a segmentation fault and out-of-bounds write because of an integer overflow via a large arrow type.
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.