ecpg can be run in a so-called Oracle compatibility mode. If this mode is active, it tries to behave as if it were Oracle Pro*C.
Specifically, this mode changes ecpg in three ways:
Pad character arrays receiving character string types with trailing spaces to the specified length
Zero byte terminate these character arrays, and set the indicator variable if truncation occurs
Set the null indicator to -1 when character arrays receive empty character string types
Read the upstream documentation. For corrections, first check the current version.