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2332. regex_iterator/regex_token_iterator should forbid temporary regexes

Section: 28.6.11 [re.iter] Status: C++14 Submitter: Stephan T. Lavavej Opened: 2013-09-21 Last modified: 2016-01-28

Priority: 2

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Discussion:

Users can write "for(sregex_iterator i(s.begin(), s.end(), regex("meow")), end; i != end; ++i)", binding a temporary regex to const regex& and storing a pointer to it. This will compile silently, triggering undefined behavior at runtime. We now have the technology to prevent this from compiling, like how reference_wrapper refuses to bind to temporaries.

[2014-02-14 Issaquah meeting: Move to Immediate]

Proposed resolution:

This wording is relative to N3691.

1. Change 28.6.11.1 [re.regiter]/1, class template regex_iterator synopsis, as indicated:

   regex_iterator();
   regex_iterator(BidirectionalIterator a, BidirectionalIterator b,
     const regex_type& re,
     regex_constants::match_flag_type m =
       regex_constants::match_default);
   regex_iterator(BidirectionalIterator a, BidirectionalIterator b,
     const regex_type&& re,
     regex_constants::match_flag_type m =
       regex_constants::match_default) = delete;
   

2. Change 28.6.11.2 [re.tokiter]/6, class template regex_token_iterator synopsis, as indicated:

   regex_token_iterator();
   regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                        const regex_type& re,
                        int submatch = 0,
                        regex_constants::match_flag_type m =
                          regex_constants::match_default);
   regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                        const regex_type& re,
                        const std::vector<int>& submatches,
                        regex_constants::match_flag_type m =
                          regex_constants::match_default);
   regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                        const regex_type& re,
                        initializer_list<int> submatches,
                        regex_constants::match_flag_type m =
                          regex_constants::match_default);
   template <std::size_t N>
   regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                        const regex_type& re,
                        const int (&submatches)[N],
                        regex_constants::match_flag_type m =
                          regex_constants::match_default);
   regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                        const regex_type&& re,
                        int submatch = 0,
                        regex_constants::match_flag_type m =
                          regex_constants::match_default) = delete;
   regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                        const regex_type&& re,
                        const std::vector<int>& submatches,
                        regex_constants::match_flag_type m =
                          regex_constants::match_default) = delete;
   regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                        const regex_type&& re,
                        initializer_list<int> submatches,
                        regex_constants::match_flag_type m =
                          regex_constants::match_default) = delete;
   template <std::size_t N>
   regex_token_iterator(BidirectionalIterator a, BidirectionalIterator b,
                        const regex_type&& re,
                        const int (&submatches)[N],
                        regex_constants::match_flag_type m =
                          regex_constants::match_default) = delete;