It looks like Freemat 4.2 crashes in some cases of stack overflow. Here is an easy-to-reproduce example (observed with 4.2 on MacOSX 10.14.4), with a recursive implementation of the Fibonacci sequence.
function u = fibrec(n) % computes the n-th term of the (0,1)-Fibonacci sequence; recursive version a = 0; b = 1; if (n == 0) u = a; elseif (n == 1); u = b; else u = fibrec(n - 2) + fibrec(n - 1); end; end
--> fibrec(5) ans = 5 --> fibrec(100)
<crash></crash>