Allow char ranges in the message_t constructor

[cacharle]

I'd like to be able to construct a message_t with std::vector<char> or other containers with a character as their value type.

I assume the condition to disallow this was to avoid conflicts with std::string and std::string_view.

[cacharle]

Not sure how to test this more (How to test that the std::string and std::string_view constructors are indeed called instead of the range one)..

[coveralls]

Pull Request Test Coverage Report for Build 21468739280

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• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 88.068%

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Change from base Build 21434492698:	0.0%
Covered Lines:	930
Relevant Lines:	1056

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💛 - Coveralls

[gummif]

Yes, so took a bit to figure recall, but the reason is string literals, so message_t("hi") is size 3, which calls the deprecated function

    template<
      class Char,
      size_t N,
      typename = typename std::enable_if<detail::is_char_type<Char>::value>::type>
    ZMQ_DEPRECATED("from 4.7.0, use constructors taking iterators, (pointer, size) "
                   "or strings instead")
    explicit message_t(const Char (&data)[N]) :
        message_t(detail::ranges::begin(data), detail::ranges::end(data))
    {
    }

So we need to be sure if we removed this overload, that the other one does not accept string literals.
Well, maybe we won't ever remove it, may mark it as = delete.
What do you think?

[cacharle]

I see, what was so wrong about this string literal constructor that it was deprecated? Seems useful to me..

Marking it as = delete seems fine. I'll check if the range constructor gets called on string literals

EDIT: indeed, message_t can be constructed from a string literal with the range constructor if I comment out the deprecated one. Marking it as = delete works`

[gummif]

Ok. What is wrong it that it includes the null character, which I would say is unexpected. So for backwards compatibility it has to be like it is I guess.