In PR #37300, Alexej asked why we the compiler does not warn about
unnecessary semicolons, e.g.
f()
{
}; // <-- here
The answer is surprising: In C++98, above syntax was disallowed but by
most compilers accepted it regardless. C++>11 introduced "empty
declarations" which made the syntax legal.
The previous behavior can be restored using flag
-Wc++98-compat-extra-semi. This finds many useless semicolons which were
removed in this change. Unfortunately, there are also false positives
which would require #pragma-s and HAS_* logic (--> check_flags.cmake) to
suppress. In the end, -Wc++98-compat-extra-semi comes with extra effort
for little benefit. Therefore, this change only fixes some semicolons
but does not enable the flag.
