clang warns when the implicit conversion changes the precision of the
converted number. in this case, the before being multiplied,
`std::numeric_limits<unsigned long>::max() >> 1` is implicitly
promoted to double so it can obtain the common type of double and
unsigned long. and the compiler warns:
```
/home/kefu/dev/scylladb/test/boost/network_topology_strategy_test.cc:129:84: error: implicit conversion from 'unsigned long' to 'double' changes value from 9223372036854775807 to 9223372036854775808 [-Werror,-Wimplicit-const-int-float-conversion]
return static_cast<unsigned long>(d*(std::numeric_limits<unsigned long>::max() >> 1)) << 1;
~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
```
but
1. we don't really care about the precision here, we just want to map a
double to a token represented by an int64_t
2. the maximum possible number being converted is less than
9223372036854775807, which is the maximum number of int64_t, which
is in general an alias of `long long`, not to mention that
LONG_MAX is always 2147483647, after shifting right, the result
would be 1073741823
so this is a false alarm. in order to silence it, we explicitly
cast the RHS of `*` operator to double.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#13221
1197664f09