BIND 10 #2705: clang unused-private-field errors

[BIND 10 Development]

#2705: clang unused-private-field errors
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                   Reporter:         |                 Owner:  UnAssigned
  jinmei                             |                Status:  new
                       Type:         |             Milestone:  Next-Sprint-
  defect                             |  Proposed
                   Priority:  very   |              Keywords:
  high                               |             Sensitive:  0
                  Component:  build  |           Sub-Project:  Core
  system                             |  Estimated Difficulty:  0
               CVSS Scoring:         |           Total Hours:  0
            Defect Severity:  N/A    |
Feature Depending on Ticket:         |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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 I noticed a few issues with upgrading clang++ (Apple's semi-proprietary
 version, seemingly based on some variant of LLVM 3.2).  It now warns
 about "unused private member variables", which caused the following:

 - it unexpectedly disable -Werror because this check now fails
 {{{
    AC_TRY_COMPILE([namespace { class Foo {}; }
    namespace isc {class Bar {Foo foo_;};} ],,
         [AC_MSG_RESULT(no)
          werror_ok=1
          B10_CXXFLAGS="$B10_CXXFLAGS -Werror"],
         [AC_MSG_RESULT(yes)])
 }}}
   We need to update the test so that it doesn't hit the "unused
   private" warning.
 - there's real "unused private" issue in our code, so if we enabled
   `-Werror`, build would fail anyway.  At least it warns about
   `LocalZoneData::class_` (in lib/cache), and I suspect there may be
   some more.  We'll need to fix them.

 Right now I'm disabling `-Werror`, but that's a bad practice and would
 like to fix this as an urgent matter.  I suggest pushing it to the
 current sprint if we run out of open tickets, or adopting it in the next
 sprint at the latest.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2705>
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