#include <boost/range/sub_range.hpp>
#include <string>
#include <vector>
using srange = boost::sub_range<std::string const>;
void func(srange) // by value
{}
int main()
{
std::string kitty{"meow"};
srange hello{kitty};
srange const& helref = hello;
func(hello);
func(helref); // line 17
return 0;
}
$ g++ -v
gcc version 9.0.0 20180626 (experimental) (GCC)
$ g++ -Wall -pedantic -Wextra -Werror -save-temps subra.cpp
subra.cpp: In function ‘int main()’:
subra.cpp:17:13: error: implicitly-declared ‘constexpr
boost::sub_range<const std::__cxx11::basic_string<char>
>::sub_range(const boost::sub_range<const
std::__cxx11::basic_string<char> >&)’ is deprecated
[-Werror=deprecated-copy]
func(helref);
^
In file included from subra.cpp:1:
/usr/include/boost/range/sub_range.hpp:259:20: note: because
‘boost::sub_range<const std::__cxx11::basic_string<char> >’ has
user-provided ‘boost::sub_range<ForwardRange>&
boost::sub_range<ForwardRange>::operator=(const
boost::sub_range<ForwardRange>&) [with ForwardRange = const
std::__cxx11::basic_string<char>]’
sub_range& operator=( const sub_range& r )
^~~~~~~~
subra.cpp:7:6: note: initializing argument 1 of ‘void func(srange)’
void func(srange) // by value
^~~~
I have two questions:
1. Why is a warning emitted only for the const srange?
2. Shouldn't boost be exempt from this warning, given that it's
included from a system directory (/usr/include) ?
Shouldn't the "implicitly declared copy constructor" error be located
at the class definition (boost header), rather than where it's being
called (the call which does pass-by-value) ?
Boost is version 1.62.0.1 packaged by Ubuntu 17.10, so I can't change that.
Csaba
Please CC me, I'm not subscribed to the list.
--
You can get very substantial performance improvements
by not doing the right thing. - Scott Meyers, An Effective C++11/14 Sampler
So if you're looking for a completely portable, 100% standards-conformat way
to get the wrong information: this is what you want. - Scott Meyers (C++TDaWYK)
