I see the following potential causes:
In #findErrorLocationsDegree:coefficients:count:fieldSize:result: the
return value in ambiguous. You make the primitive fail if not enough
errors are found. But after the send, you don't check for failure
but simply send #methodReturnReceiver.
Instead, you should either check for primitive failure after the send
or make #findErrorLocationsDegree:coefficients:count:fieldSize:result:
return boolean value: the method was successful or not.
E.g. when numErrors = 1, return true, in the other branch, return e =
numErrors. (If slang doesn't support boolean types, just use 0 and 1).
In the actual primitive method, check for the value returned by that
method and fail the primitive when needed. Once the primitive has failed,
you ought to return from it.
I see the above pattern in other methods too (marking the primitive as
failed in a not-top-level method without checking for failure outside).
Those need to be fixed as well.
Another potential issue I see is that the validation of the arguments is
E.g.: #stackIntegerValue: may have already set the primitive to failed if
the argument was not an integer. So, before continuing, that has to be
Another possible but unlikely problem is that you assume that both result
and coefficients have at least one field. But that may not be true which
can result in segfaults.