Found the following significant warnings:
  :909:10: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  956:10: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  35: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  :10: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  : warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  10: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  :551:10: warning: 'long long' is a C++11 extension [-Wc++11-long-long]#  define BOOST_MATH_INT_VALUE_SUFFIX(RV, SUF) RV##SUF
  :35: warning: 'long long' is a C++11 extension [-Wc++11-long-long]      boost::int64_t(     30LL),
  118:25: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  :94:35: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  :95:35: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  :124:25: warning:       boost::int64_t(         -3617LL),'long long' is a C++11 extension [-Wc++11-long-long]
  28: warning: 'long long' is a C++11 extension [-Wc++11-long-long]      boost::int64_t(        +43867LL),
  26: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  915:10: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  95:35: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  28: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  23: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  113:28: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  27: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  :23: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
  663:35: warning:       boost::int32_t(            -1LL),'long long' is a C++11 extension [-Wc++11-long-long]
  664:32: warning:       boost::int32_t(            +1LL),'long long' is a C++11 extension [-Wc++11-long-long]
  665:31: warning:       boost::int32_t(            -1LL),'long long' is a C++11 extension [-Wc++11-long-long]
  :30: warning: 'long long' is a C++11 extension [-Wc++11-long-long]      boost::int32_t(          -691LL),
  665:31: warning:       boost::int32_t(      1LL),'long long' is a C++11 extension [-Wc++11-long-long]
  30: warning: 'long long' is a C++11 extension [-Wc++11-long-long]      boost::int32_t(      6LL),
  30: warning: 'long long' is a C++11 extension [-Wc++11-long-long]      boost::int32_t(     30LL),
  677:27: warning:       boost::int32_t(      1LL),'long long' is a C++11 extension [-Wc++11-long-long]
  :26: warning:       boost::int32_t(     42LL),'long long' is a C++11 extension [-Wc++11-long-long]
  :679:28: warning: 'long long' is a C++11 extension [-Wc++11-long-long]
See ‘/data/gannet/ripley/R/packages/tests-clang/rstanarm.Rcheck/00install.out’ for details.