Found the following significant warnings:
  /usr/local/clang/include/google/protobuf/io/coded_stream.h:695:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/arenastring.h:246:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/arenastring.h:248:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/repeated_ptr_field.h:281:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/repeated_ptr_field.h:295:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/repeated_ptr_field.h:667:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/repeated_ptr_field.h:738:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/inlined_string_field.h:205:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/inlined_string_field.h:207:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:128:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:139:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:148:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:154:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:162:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:171:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:176:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:181:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:184:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:365:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:408:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:411:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:431:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:527:1: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:661:1: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:790:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:795:1: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:841:1: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:862:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:864:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:866:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:868:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:870:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:872:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:874:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:878:1: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:894:1: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:908:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:910:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:912:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:914:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:916:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:918:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:920:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:924:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:929:17: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/extension_set.h:292:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/extension_set.h:297:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/extension_set.h:367:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/extension_set.h:587:5: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/extension_set.h:1381:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./geobuf.pb.h:298:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./geobuf.pb.h:313:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./geobuf.pb.h:972:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./geobuf.pb.h:990:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./geobuf.pb.h:1225:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./geobuf.pb.h:1243:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./geobuf.pb.h:1261:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./mvt.pb.h:230:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./mvt.pb.h:405:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./mvt.pb.h:925:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./mvt.pb.h:1048:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./mvt.pb.h:1429:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/message.h:503:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
   /usr/local/clang/include/google/protobuf/extension_set.hwarning: :use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]292
  :3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/extension_set.h/usr/local/clang/include/google/protobuf/extension_set.h::13811381::33::  warning: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./rexp.pb.h:515:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./rexp.pb.h:533:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  ./rexp.pb.h:721:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/message.h:658:3: warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
  /usr/local/clang/include/google/protobuf/parse_context.h:527:1: In file included from warning: unserialize.cppuse of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]:
  warning: use of the 'nodiscard' attribute is a C++17 extension [-Wc++17-attribute-extensions]
See ‘/data/gannet/ripley/R/packages/tests-clang/protolite.Rcheck/00install.out’ for details.