Although it's an early (and wild) guess, if the segfault occurs with a large set of data, but not a small set, I would suspect a buffer overrun may be the cause of your problems. Are you...
(1) Putting too much on the stack (versus dynamically allocating the space you need), or
(2) Exceeding the space you allocated?
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
Although it's an early (and wild) guess, if the segfault occurs with a large set of data, but not a small set, I would suspect a buffer overrun may be the cause of your problems. Are you...
(1) Putting too much on the stack (versus dynamically allocating the space you need), or
(2) Exceeding the space you allocated?