How to replace std::string with vstring?

Question

I recently learned, that since a few years the library libstdc++ contains vstring (also known as versa_string), which provides the same functionality as std::string, but is apparently more conforming to the C++ standard. I have tried to use vstring as a replacement for std::string, but I have found no easy way to do it.

Is there an easy way to replace std::string with vstring, without changing the libstdc++ sources?

I am fine with replacing all uses of std::string within my code by an alias, as indicated by the following listing. However, the problem with this approach is, that std::string is also used internally in some places, e.g. in std::ostringstream. That means, the statements std::ostringstream os; my::string s = os.str(); no longer works.

namespace my {
#ifdef __GLIBCXX__
    using string = __gnu_cxx::__vstring;
#else
    using string = std::string;
#endif
}

Stationmaster

Recent version ? vstring was added in 4.1. See https://mcmap.net/q/427724/-what-is-gcc-39-s-quot-vstring-quot. – Dwarfish

I seem to remember Herb Sutter saying in some video that gcc4.9 was going to make std::string non-ref counted, but I don't see that in the release notes. You can fix the error in the one case you've listed by using my::string s = os.str().c_str(); instead. There might even be a way to access the underlying streambuf to avoid the intermediate std::string, but I'm not sure of that part. – Lodhia

@Praetorian: JW said it wouldn't make 4.9 #21432133 – Clowers

Indeed, rumours of the COW string's death have been greatly exaggerated ;-) To answer the question, no, there is no way to replace std::string in the library. You'll have to wait for GCC 4.10 – Sociology

@JonathanWakely: I think you could make this an answer. – Apomict

Answer 1

No, there is no way to replace std::string with vstring, it's meant as an alternative string type, not a drop-in replacement for std::string

Since GCC 5.1 the library ships with two implementations of std::string and for any given translation unit you can choose which to use via the _GLIBCXX_USE_CXX11_ABI macro. The two string types have different mangled names, so are not link-compatible.

See Dual ABI for more details.

Sociology

Would you mind updating this answer given how GCC has progressed since 2014? – Exodontics