std::string exception safety guarantees?

For the life of me, I cannot find anything in the C++ standard that
says what the value of s is after this code, assuming that the resize
*does* throw an exception:

     std::string s("Here is a short string");
     std::string s1 = s;
     try {
         s.resize(s.max_size() + 1); // will throw length_error
exception.
     catch(...) {
     }

I'd expect that s == s1 holds after catching the exception, but there
seems to be no guarantee in the C++ standard. (Of course, any
implementation I know attempts to allocate, without modifying the
string.)

The closest it comes to offering any guarantees is 21.3, para 3: "3
The class template basic_string conforms to the requirements for a
Sequence (23.1.1) and for a Reversible Container (23.1)." However,
the chapter 23 only says, on the topic of exceptions:

23.1, para 10: Unless otherwise specified (see 23.2.2.3 and 23.2.5.4)
all container types defined ***in this clause*** (emphasis mine) meet
the following additional requirements: - if an exception is thrown
by...

I take it as saying that this paragraph has *no* implication on
std::basic_string, as it does not define a requirement of Sequence nor
Reversible Container.

Would someone please either 1. point to the relevant language, 2.
share knowledge of an implementation where string does not offer the
strong exception guarantee, 3. point me to the relevant LWG Issue, or
4. encourage me to file one? :)

Thanks for any feedback,
--
Herve Bronnimann

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