[Bug libstdc++/64585] New: The basic_regex object should not match any character sequence after a call to basic_regex::imbue

["kariya_mitsuru at hotmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64585

            Bug ID: 64585
           Summary: The basic_regex object should not match any character
                    sequence after a call to basic_regex::imbue
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kariya_mitsuru at hotmail dot com

Created attachment 34437
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34437&action=edit
g++ -v

Please see the following sample.

=============================== sample code ===============================
#include <iostream>
#include <regex>

int main()
{
    static const char s[] = "";
    std::regex re("");
    std::cout << std::boolalpha << std::regex_search(s, re) << std::endl;

    auto loc = re.imbue(re.getloc());
    std::cout << std::boolalpha << std::regex_search(s, re) << std::endl;
}
===========================================================================

================================= output ==================================
true
true
===========================================================================

cf. http://melpon.org/wandbox/permlink/0wKMiCY8uNEhOecE


The C++11 standard 28.8.5[re.regex.locale]/p.1 says, "After a call to imbue the
basic_regex object does not match any character sequence."

So I think that the output should be

================================= output ==================================
true
false
===========================================================================