[Bug c++/80711] warn on non-const accessor member functions

["dcb314 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80711

--- Comment #8 from David Binderman <dcb314 at hotmail dot com> ---
(In reply to Jonathan Wakely from comment #7)
> struct indirect_cmp {
>   static int counter;
>   bool operator()(const X* l, const X* r) {
>     ++counter;
>     return *l < *r;
>   }
> };
> 
> int indirect_cmp::counter = 0;
> 
> So the pure attribute isn't the right property.

I tried your code on cppcheck and much to my surprise it found
the problem:

$ /home/dcb/cppcheck/trunk//cppcheck --enable=all --inconclusive may9a.cc
may9a.cc:4:8: style:inconclusive: Technically the member function
'indirect_cmp::operator()' can be const. [functionConst]
  bool operator()(const X* l, const X* r) {
       ^
$

My working assumption had been that cppcheck was looking for C++
member functions that consist of a return statement only but clearly
it is doing more than that. 

If there is any interest, I could probably figure out the pattern of C++ 
code it is looking for.

My opinion is that a first approximation at implementation in gcc would
merely look for C++ member functions that are return statements only.
More fancy things could be done later in a second version.