‘multiline’ is not a member of ‘std::__cxx11::regex’

Question

I am trying to compile the following C++ code using the command:

g++ -std=c++17 -o rgx rgx.cpp

#include <iostream>
#include <regex>
#include <string>
using namespace std;

int main() {
        regex rgx("^([A-Z]*)$", regex::ECMAScript | regex::multiline | regex::icase);
        smatch rmtch;
        string str = "AbcefgH\r\nTest";
        if (regex_match(str, rmtch, rgx)) {
                for (size_t i = 0; i < rmtch.size(); i++) {
                        ssub_match smtch = rmtch[i];
                        string s_m = smtch.str();
                        cout << " submatch " << i << ": " << s_m << endl;
                }
        }
        return 0;
};

However get the following compile time error

rgx.cpp: In function ‘int main()’:
rgx.cpp:7:53: error: ‘multiline’ is not a member of ‘std::__cxx11::regex’ {aka ‘std::__cxx11::basic_regex<char>’}
    7 |  regex rgx("^([A-Z]*)$", regex::ECMAScript | regex::multiline | regex::icase);

g++ --version
g++ (Ubuntu 9.1.0-8ubuntu1) 9.1.0

Why is g++ using __cxx11::regex when I've specified -std=c++17?

cppreference.com/w/cpp/regex/basic_regex defines regex::multiline as being part of the C++17 standard

Looks like the standard library you're using hasn't been updated to include all the C++17 additions yet. — Jerry Coffin, Jul 16 '19 at 00:01
If this is the case, how am I supposed to use multiline regex? — IcySi, Jul 16 '19 at 00:28
One obvious choice would be to find a different regex library that supports what you want. Another would be to recognize a multiline regex as a number of consecutive single-line regexes. — Jerry Coffin, Jul 16 '19 at 05:15

score 0 · Answer 1 · answered Jul 15 '19 at 23:56

Libstdc++ doesn't appear to implement regex::multiline.

Note that the fact that it's using std::__cxx11::regex doesn't mean that you're stuck in the past. __cxx11 is not strictly reserved to C++11 features. The purpose of inline namespaces (such as __cxx11) is that if eventually a class/struct needs to change in ways that are not backwards compatible, new programs will grab its definition from a new inline namespace while the old definition remains for programs that were built before.

Interesting, I'm wondering why that would be if I'm running on the latest gcc build from eoan ubuntu packages repository? — IcySi, Jul 16 '19 at 00:09

‘multiline’ is not a member of ‘std::__cxx11::regex’

1 Answers1