Version 6.7.3 of the ASN1C ASN.1 compiler was recently released.  This is a patch release that fixed a number of issues.  Support of "zero-on-free" as documented in a recent blog post was implemented.  In addition, some bugs related to the use of the -linkedlist command-line option were resolved.  For a complete list of changes that went into the release, please check out the change log.  Customers with active support can get access to the new release by logging into their online account and seeing if it is available.  If not, please contact us and we will provide access.