regex in g++ and VS2012

Question

#include <iostream>
#include <string>
#include <regex>

using namespace std;

void Test(const char* str, const char* regExpression)
{
    regex rx(regExpression);
    bool match = regex_match(str, rx);
    bool search = regex_search(str, rx);

    cout << "String: " << str << "  expression: " << regExpression <<
        "   match: " << (match ? "yes" : "no ") <<
        "   search: " << (search ? "yes" : "no ")  << endl;
}


int main()
{
    Test("a", "a");
    Test("a", "abc");
    return 0;
}

Results in g++:

String: a  expression: a   match: yes   search: no 
String: a  expression: abc   match: no    search: no

Results in VS2012:

String: a  expression: a   match: yes   search: yes
String: a  expression: abc   match: no    search: no

What is correct result?. Also, what is the difference between regex_match and regex_search?

us2012 · Accepted Answer · 2013-03-03 12:12:05Z

2

The VS2012 results are right. _match checks whether your string matches the expression, _search checks whether some substring of your string matches the expression.

Neither "a" nor any substring of "a" match the expression "abc".

(I can't find the relevant SO question, but gcc's (rather, libstdc++'s) regex implementation is known to be buggy and incomplete.)

edited Mar 3, 2013 at 12:12

answered Mar 3, 2013 at 12:05

us2012

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3 Comments

Alex F Over a year ago

Shame on me, I just used Test parameters in incorrect order :(

jogojapan Over a year ago

No need for an SO question; it's described on the standard library support table for GCC (see '28, Regular expressions')

Jonathan Wakely Over a year ago

See stackoverflow.com/questions/12530406/… and stackoverflow.com/a/4716974/981959 and loads more questions

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