BIND 10 #2272: Improve the perfdhcp command_options_helper code.

[BIND 10 Development]

#2272: Improve the perfdhcp command_options_helper code.
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                   Reporter:         |                 Owner:  UnAssigned
  marcin                             |                Status:  assigned
                       Type:         |             Milestone:  Sprint-
  defect                             |  DHCP-20121004
                   Priority:         |            Resolution:
  medium                             |             Sensitive:  0
                  Component:         |           Sub-Project:  DHCP
  Unclassified                       |  Estimated Difficulty:  0
                   Keywords:         |           Total Hours:  0
            Defect Severity:  N/A    |
Feature Depending on Ticket:         |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Changes (by marcin):

 * owner:  marcin => UnAssigned
 * status:  new => assigned


Comment:

 The command_options_unit tests prepare certain number of perfdhcp command
 lines in the string format like "perfdhcp -l eth0 -4 all". Each new
 command line is later tokenized and stored in argc, argv variables. The
 argc, argv is allocated for each new command line being tested in
 command_options_helper.h by CommandOptionsHelper::tokenizeString() and
 then it is passed to CommandOptions::parse() for parsing.

 The getopt() function used in parse() function keeps its internal state
 including optind, opterr etc. during parsing subsequent arguments of the
 command line. It also appears that getopt() remembers the pointer of the
 previously used argv buffer and if getopt() state is not properly reset
 before parsing new command line it will refer to freed memory and that
 will eventually lead to undefined behavior and output from getopt().

 There are at least two ways to reset the state of the getopt() to prevent
 it from trying to access freed buffers. On Linux: the optind must be set
 to 0. This however does not work on BSD and MacOS where there is an
 additional variable declared: optreset. On those systems both optreset and
 optind must be set to 1.

 The key of the change being done here is to check if optreset is available
 on the OS we are at and if so, define the HAVE_OPTRESET so as the code can
 take different reset path based on this. The code also now uses new/delete
 instead of malloc/free to allocate the argv table which is more proper
 when programming in C++. Some additional minor changes have been made.

 Please review.

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Ticket URL: <http://bind10.isc.org/ticket/2272#comment:2>
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