c++ - Is gcc 4.8 or earlier buggy about regular expressions?

Question

I am trying to use std::regex in a C++11 piece of code, but it appears that the support is a bit buggy. An example:

#include <regex>
#include <iostream>

int main (int argc, const char * argv[]) {
    std::regex r("st|mt|tr");
    std::cerr << "st|mt|tr" << " matches st? " << std::regex_match("st", r) << std::endl;
    std::cerr << "st|mt|tr" << " matches mt? " << std::regex_match("mt", r) << std::endl;
    std::cerr << "st|mt|tr" << " matches tr? " << std::regex_match("tr", r) << std::endl;
}

outputs:

st|mt|tr matches st? 1
st|mt|tr matches mt? 1
st|mt|tr matches tr? 0

when compiled with gcc (MacPorts gcc47 4.7.1_2) 4.7.1, either with

g++ *.cc -o test -std=c++11
g++ *.cc -o test -std=c++0x

or

g++ *.cc -o test -std=gnu++0x

Besides, the regex works well if I only have two alternative patterns, e.g. st|mt, so it looks like the last one is not matched for some reasons. The code works well with the Apple LLVM compiler.

Any ideas about how to solve the issue?

Update one possible solution is to use groups to implement multiple alternatives, e.g. (st|mt)|tr.

Answer 1