Found the following significant warnings:
  swmm5_iface.cpp:99:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:108:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:117:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:126:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:59:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:60:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:61:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:62:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:63:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:67:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:84:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:85:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:86:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:87:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:88:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:89:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:138:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:140:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:142:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:144:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:149:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:150:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
  swmm5_iface.cpp:207:5: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
See '/home/hornik/tmp/R.check/r-devel-clang/Work/PKGS/swmmr.Rcheck/00install.out' for details.