BIND 10 #972: Resolver class is not exception safe

[BIND 10 Development]

#972: Resolver class is not exception safe
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            Reporter:  jinmei    |                        Owner:
                Type:  defect    |                       Status:  new
            Priority:  major     |                    Milestone:  New Tasks
           Component:  resolver  |                     Keywords:
           Sensitive:  0         |              Defect Severity:  N/A
         Sub-Project:  DNS       |  Feature Depending on Ticket:
Estimated Difficulty:  0         |          Add Hours to Ticket:  0
         Total Hours:  0         |                    Internal?:  0
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 As I looked at the code for #971, I noticed another problem in the
 Resolver class: Its constructor is not exception safe:

 {{{
 Resolver::Resolver() :
     impl_(new ResolverImpl()),
     dnss_(NULL),
     checkin_(new ConfigCheck(this)),
     dns_lookup_(new MessageLookup(this)),
     dns_answer_(new MessageAnswer),
     nsas_(NULL),
     cache_(NULL),
     configured_(false)
 {}
 }}}

 If, for example, "new ConfigCheck" fails, the allocated resource for
 impl_ will leak.

 It also looks quite awkward that it has specific member variables even
 if it adopts the pimpl idiom (although there may be a specific reason
 that can only be understood via deep understanding of the
 implementation details).

 Furthermore, due to the fact that dnss_/nsas_/cache_ are not set (to a
 non NULL value) at the construction time this class is quite fragile
 because some methods naively assumes they are non NULL.  Example:

 {{{
 void
 Resolver::setForwardAddresses(const AddressList& addresses)
 {
     impl_->setForwardAddresses(addresses, dnss_);
 }
 }}}

 I'd suggest heavy refactoring and cleanup for this class so that it
 will be cleaner and safer.

-- 
Ticket URL: <http://bind10.isc.org/ticket/972>
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