[cdp] memcpy_with_check() bug?

[Peter P.]

Dear list,

I saw someone produce an error with a call of 
 extend zigzag 1 k.wav kz.wav 0 57 180 0.1
that resulted in a few seconds of processing and then an error message
 ERROR: INTERNAL ERROR: (Bug?)
 ERROR: ATTEMPTED to copy -ve number of bytes: memcpy_with_check()

I tried to reproduce this on wine with the original soundfile but didn't
managed to.

Has anyone ever seen such an error message and could explain what it
means?

Thank you so much!
Peter