coverity scan AUTO_CAUSES_COPY findings

[Arne Welzel]

Coverity reported warnings around AUTO_USES_COPY zeek/zeek#2341.

Just pasting here from an email, happy to just do them if they seem like reasonable reportings. @Neverlord ?

*** CID 1491340:  Performance inefficiencies  (AUTO_CAUSES_COPY)
/home/runner/work/zeek/zeek/auxil/broker/bindings/python/set_bind.h: 98 in _ZZN8pybind116detail25set_if_insertion_operatorISt3setIN6broker4dataESt4lessIS4_ESaIS4_EENS_6class_IS8_JSt10unique_ptrIS8_St14default_deleteIS8_EEEEEEEDTcmlsclsr3stdE7declvalIRSoEEclsr3stdE7declvalINT_10value_typeEEEcvvLi0EERT0_RKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEENKUlRS8_E_clB5cxx11EST_()
92       cl.def(
93         "__repr__",
94         [name](Set& s) {
95           std::ostringstream t;
96           bool first = true;
97           t << name << "{";
>>>     CID 1491340:  Performance inefficiencies  (AUTO_CAUSES_COPY)
>>>     Using the "auto" keyword without an "&" causes the copy of an object of type data.
98           for (auto i : s) {
99             if (!first)
100               t << ", ";
101             t << i;
102             first = false;
103           }

home/runner/work/zeek/zeek/auxil/broker/include/broker/internal/with_native_labels.hh: 25 in broker::internal::with_native_labels<broker::telemetry::int_histogram_get_or_add(broker::telemetry::metric_family_hdl *, broker::span<const std::pair<std::basic_string_view<char, std::char_traits<char>>, std::basic_string_view<char, std::char_traits<char>>>>)::[lambda(T1) (instance 1)]>(broker::span<const std::pair<std::basic_string_view<char, std::char_traits<char>>, std::basic_string_view<char, std::char_traits<char>>>>, T1)()
19         };
20         for (size_t index = 0; index < xs.size(); ++index)
21           buf[index] = ct::label_view{xs[index].first, xs[index].second};
22         return continuation(span{buf, xs.size()});
23       } else {
24         std::vector<ct::label_view> buf;
>>>     CID 1491339:    (AUTO_CAUSES_COPY)
>>>     Using the "auto" keyword without an "&" causes the copy of an object of type pair.
25         for (auto x : xs)
26           buf.emplace_back(x.first, x.second);
27         return continuation(span{buf});
28       }
29     }

/home/runner/work/zeek/zeek/auxil/broker/include/broker/internal/with_native_labels.hh: 40 in broker::internal::with_native_labels<broker::telemetry::<unnamed>::impl_base::int_histogram_fam(std::basic_string_view<char, std::char_traits<char>>, std::basic_string_view<char, std::char_traits<char>>, broker::span<const std::basic_string_view<char, std::char_traits<char>>>, broker::span<const long>, std::basic_string_view<char, std::char_traits<char>>, std::basic_string_view<char, std::char_traits<char>>, bool)::[lambda(T1) (instance 1)]>(broker::span<const std::basic_string_view<char, std::char_traits<char>>>, T1)()
34         caf::string_view buf[10];
35         for (size_t index = 0; index < xs.size(); ++index)
36           buf[index] = xs[index];
37         return continuation(span{buf, xs.size()});
38       } else {
39         std::vector<caf::string_view> buf;
>>>     CID 1491339:    (AUTO_CAUSES_COPY)
>>>     Using the "auto" keyword without an "&" causes the copy of an object of type basic_string_view.
40         for (auto x : xs)
41           buf.emplace_back(x);
42         return continuation(span{buf});
43       }
44     }
45  

[Dominik Charousset]

happy to just do them if they seem like reasonable reportings

@awelzel I'd appreciate it if you'd file a PR! The last two are probably inconsequential, since a string view is just a pointer and a size. I'd fix them regardless, though. Using the const-ref doesn't hurt either and making the static analyzers happy is worth it.