Strange results when using C++11 regexp with gcc 4.8.2 (but works with Boost regexp)

c++ regex gcc c++11 gcc4.8
Philipp Claßen picture Philipp Claßen · Nov 17, 2013 · Viewed 8.1k times · Source

I tried to use C++11's regular expression but failed even in trivial examples. From the outside, it seems to only compare the strings, for example:

std::regex_match(std::string{""}, std::regex{"a?"})   // false (???)
std::regex_match(std::string{"a?"}, std::regex{"a?"}) // true  (???)

In contrast, the Boost's regexp library behaves as I would have expected:

boost::regex_match(std::string{""}, boost::regex{"a?"})   // true  (OK)
boost::regex_match(std::string{"a?"}, boost::regex{"a?"}) // false (OK)

I tested with GCC 4.8.2 and clang 3.4 (also using GCC's STL library). Either the library is broken, or I do not understand the syntax defined by the C++11 standard.

Answer

Joe Z picture Joe Z · Nov 17, 2013

It's not supported in GCC 4.8.x. Check out the corresponding Bugzilla entry:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53631

Specifically: "Now regex is implemented. Should come with GCC 4.9 :)"

Related questions

Is gcc 4.8 or earlier buggy about regular expressions?

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[]) { …

Read More
C++: what regex library should I use?

I'm working on a commercial (not open source) C++ project that runs on a linux-based system. I need to do some regex within the C++ code. (I know: I now have 2 problems.) QUESTION: What libraries do people who regularly do …

Read More
How to get substring from a string in qt?

I have a text form: Last Name:SomeName, Day:23 ...etc From Last Name:SomeName, I would like to get Last Name, and separately SomeName. I have tried to use QRegularExpression, QRegularExpression re("(?<label>\\w+):(?<text>\\w+)"); …

Read More