var_vacm_access() question

Hi,
I'm one of the volunteer developers with ICEI (please see email with
subject "ICEI asks what help you need" for details). I was attempting
to compile net-snmp code with -std=c99 compiler option, and the
compiler failed with "error: overflow in implicit constant conversion
[-Werror=overflow] on the following lines in
net-snmp-code/agent/mibII/vacm_vars.c: 382, 397, and 593. These 3
locations have *cp++ = 255;

So, my question is where can I get more information on
var_vacm_access(). It appears to me it has something to do with
determining group access control for a MIB group. Specifically, what
is the rational for incrementing, then basically setting the location
pointed by "cp" to 255 given the if logic above each of the 3
locations where *cp++ = 255 is set.

Thanks,
Keith

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