On 05/04/2017 05:10 AM, Jonathan Wakely wrote:
On 4 May 2017 at 07:32, Xi Ruoyao wrote:
On 2017-05-03 11:26 +0100, Jonathan Wakely wrote:
On 3 May 2017 at 05:41, Xi Ruoyao wrote:
In template metaprogramming, we may write something like
~~~~~
template <typename A, typename B>
struct BetterType
{
typedef If<(Priority<A>::value > Priority<B>::value), A, B>::type type;
};
~~~~~
However, GCC -Wenum-compare (enabled by default) would complain
at each POT of BetterType. It seems annoying.
Of course we can cast the operands of compare to int. But should we
make GCC more clever and not to complain this causal idiom?
You're comparing unrelated enumeration types, which is what the
warning is designed to warn about. Why should it not warn just because
it's in a template?
No. My point is, in this "enum hack" case we just use the enum values as
integer constants, not because they are in templates.
Maybe we could silence the warning for the enums has only one
enumerator with assigned value.
I suppose it could, but that would mean we fail to warn in cases where
we should be warning e.g.
If I understand the correctly the suggestion is to avoid warning
for comparison of enumerators of different types (not objects of
the enumerated types).
Assuming the code defines the enums as unnamed types, comparing
their enumerators seems unlikely to be a problem. Or can you
think of some accidental misuse that the warning would detect?
If there isn't one it might to detect the (legacy) idiom and
suppress the warning in that case. Or add a warning suboption
to control it, until the code transitions to the more modern
way of doing things. Or perhaps only warn in C++ 11 mode and
later.
Martin
