GLIBCXX errors, a very few ports don't run

[Jeffrey Bouquet]

command: lnav -s
/usr/local/lib/gcc47/libstdc++.so.6: version GLIBCXX_3.4.20 required by /usr/local/bin/lnav not found

Script done on Sat Apr  4 04:56:17 2015


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10.1-STABLE r280322
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gcc-4.8...
gcc-ecj-4.5
gcc47-4.7...
gcc49-4.9...
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Anyone know of the best practices to trim down/reconfigure the set of compilers one has installed so the
GLIBCXX/libstdc issue which sometimes appears goes away eventually, or is remedied by a libmap.conf ?
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Or any similar fix?

Thanks.