C++11 regexp works in MSVC, gives errors in gcc [duplicate]

This question already has an answer here:

• strange behaviour of regex in c++11 under linux 1 answer

I'm using a regex to separate the fields of an HTTP request:

GET /index.asp?param1=hello&param2=128 HTTP/1.1

This way:

smatch m;
try 
{ 
    regex re1("(GET|POST) (.+) HTTP"); 
    regex_search(query, m, re1); 
} 
catch (regex_error e) 
{ 
    printf("Regex 1 Error: %d\n", e.code()); 
}
string method = m[1]; 
string path = m[2];

try 
{ 
    regex re2("/(.+)?\\?(.+)?"); 
    if (regex_search(path, m, re2)) 
    { 
        document = m[1]; 
        querystring = m[2];
    }
} 
catch (regex_error e) 
{ 
    printf("Regex 2 Error: %d\n", e.code()); 
}

If I run this code in Windows, it works. Run it in Linux (Ubuntu Server 14.04 with GCC version 4.8.2) and I get the error code 2:

regex_error(error_escape): The expression contained an invalid escaped character, or a trailing escape.

I just don't know where the error is, the expression looks correct to me. Can you suggest a better expression or a different method of splitting that string?