Get rid of gcc warning -Wnon-virtual-dtor

[wbangna]

We get warnings when compiling the jsonpath extension:
... has accessible non-virtual destructor [-Wnon-virtual-dtor]

Simply defining a defaulted virtual destructor for the base class binary_operator removes the warning.

[danielaparker]

Thanks for noting this. Going forward, we'll compile the gcc tests with the -Wnon-virtual-dtor compile flags.

I believe though that the binary_operator specializations don't require a public virtual destructor, because they're never destroyed through a pointer to a base class. Could you try an alternative approach to silence the warning, by making the base destructor non-virtual but protected? i.e.

protected:
~binary_operator() = default;

Thanks,
Daniel

[wbangna]

Thank you for your suggestion. I guess that it's safe to have a non-virtual destructor since the class is in the namespace detail.
I changed the destructor as you suggested and tested it with a small test program.

[danielaparker]

Thank you for your suggestion. I guess that it's safe to have a non-virtual destructor since the class is in the namespace detail.
I changed the destructor as you suggested and tested it with a small test program.

Thanks.

[danielaparker]

Thanks, merged (after I initially forgot to merge it before closing it!) The main reason for making it non-virtual protected is that it documents and enforces an internal design choice.

[danielaparker]

I added -Wnon-virtual-dtor in the build tests, and there a few other cases like that in the jsonschema and jmespath extension. I'll fix those.