Not many:

- incorrect results in rare cases if using malloc
  => default for ADOL-C memory allocation changed to calloc

- operations like adouble=value/adouble, adouble=value*adouble, etc. that
  overwrite the adouble argument cause either a segmentation fault, an error
  in seeking/reading the taylor stack or wrong derivatives when applying the
  reverse mode (only one taylor gets written but two are read back)