messages: fix out of range assertion

[jcsp]

clang detects that this is invalid (presumably
using an 8 bit type for the enum)

Signed-off-by: John Spray john.spray@redhat.com

[wjwithagen]

@jcsp
Can't fool Clang :)

/usr/srcs/Ceph/work/ceph/src/messages/MMgrReport.h:39:17: warning: comparison of constant 255 with expression of type 'const enum perfcounter_type_d' is always true
[-Wtautological-constant-out-of-range-compare]
assert(type <=255);
~~~~ ^ ~~~

[jcsp]

Gaaah!

[jcsp]

I don't really want to remove the assert, because there's no guarantee the enums are always going to be char-sized :-/

[liewegas]

If that still triggers a clang warning we can just change it to 254, which should be just as effective.

[tchaikov]

or we can declare the perfcounter_type_d as

enum class perfcounter_type_d : uint8_t {
 // ...
}

[wjwithagen]

@tchaikov @liewegas @jcsp
I did not make it a enum class, but did add the : uint8_t in the declaration.
Clang is now happy.

And I think it also can get ride of a lot of the casts like:
::encode((uint8_t)type, bl)

Have not run it thru GCC

[wjwithagen]

@tchaikov @liewegas @jcsp
Right, removing the casts actually throws Clang into a selction problem on which of the many en/decode options it can promote to to actually get the work done.
So removing the casts is not an option.

[tchaikov]

@wjwithagen yeah, less code churn if unscoped version is used, or instead of keeping the casts, we can add

template<typename E,
         typename std::enable_if<std::is_enum<E>{}>::type* = nullptr>
void encode(E e, bufferlist& bl) {
  encode(static_cast<typename std::underlying_type<E>::type>(e), bl);
}

to delegate the encode() calls applying to the enum types to their underlying types.

[jcsp]

Updated this to always use uint8_t for the enum, and just assert on the size of the resulting type (the assertion is still strictly always true, so let's see if clang complains about that too!)

[tchaikov]

nit, could be static_assert().

[jcsp]

done

[tchaikov]

could be

static_assert (sizeof(type) == 1 , "enum type declared as uint8_t");

static_assert ( bool_constexpr )    //  (since C++17)

[tchaikov]

lgtm.