./upptest.h:97:15: error: exception specification of overriding function is more lax than base version
                const char* what() const override { return _msg.c_str(); }
                            ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/exception.h:75:5: note: overridden virtual function is here
    what() const _GLIBCXX_TXN_SAFE_DYN _GLIBCXX_NOTHROW;
    ^
1 error generated.

In file included from play.cpp:5:
upptest.h:97:15: error: looser throw specifier for ‘virtual const char* utest::assert_fail_exception::what() const’
   97 |   const char* what() const override { return _msg.c_str(); }
      |               ^~~~
In file included from /usr/include/c++/9/exception:38,
                 from upptest.h:51,
                 from play.cpp:5:
/usr/include/c++/9/bits/exception.h:75:5: note: overridden function is ‘virtual const char* std::exception::what() const noexcept’
   75 |     what() const _GLIBCXX_TXN_SAFE_DYN _GLIBCXX_NOTHROW;
      |     ^~~~
In file included from play.cpp:5:
upptest.h:146:15: error: declaration of ‘const utest::info* utest::result::info’ changes meaning of ‘info’ [-fpermissive]
  146 |   const info* info;
      |               ^~~~
upptest.h:114:8: note: ‘info’ declared here as ‘class utest::info’
  114 |  class info;
      |        ^~~~
upptest.h:147:10: error: declaration of ‘utest::status utest::result::status’ changes meaning of ‘status’ [-fpermissive]
  147 |   status status;
      |          ^~~~~~
upptest.h:107:13: note: ‘status’ declared here as ‘enum class utest::status’
  107 |  enum class status
      |             ^~~~~~