Building regex by vector of others

[asergunov]

Hello.

I need to find which regex of N my string matches.

It's easy to implement if I have them compile time:

sregex re = (s1 = re1)|(s2 = re2)|(s3=re3);
...
std::set<int> foo(const std::string& str) {
 std::set<int> result;
 smatch match;
 if(regex_match(str, match, re)) {
 for(int i = 0; i<3; ++i)
  if(match[i+1]) result.insert(i);
 }
return result;
}

But I have a vector:

std::set<int> foo(const std::string& str, const std::vector<sregex>& reVector) {
 sregex re;
 int index = 1;
 for(auto&& item : reVector) {
   re |= (mark_tag(index++) = item); // (1)
 }

 std::set<int> result;
 smatch match;
 if(regex_match(str, match, re)) {
  for(int i = 0; i<reVector; ++i)
    if(match[i+1]) result.insert(i);
  }
 }
return result;
}

There at (1) |= doesn't work as I expect for some reson, It didn't catch some values.
If I replace it with

 re = re | (mark_tag(index++) = item);

it just crashes. If I replace with:

 auto t = re;
 re = t | (mark_tag(index++) = item);

it making captures of previous tags to be subexpresions matches. So code doesn't work as I want.

Is it any way to prevent sub-expression capture isolation?

As I understand it should be some intermediate type before sregex to express expression under construction. So it will not isolate matches of existing part.

I'm using v1.65.1