Why are RB-trees used to implement std::set?

[Brian Budge]

> Break binary compatibility?  What kind of guarantees are there?  I'm
> not advocating a change in data structures, but it doesn't seem like
> there are any promises beyond API conformance, are there?


Imagine you write a library and you compile and distribute the
binaries.  Someone else builds against those.  If std::set is used in
your API, and they have a different version of libstdc++, do you still
want the library and the binary to be compatible, even across
different versions of libstdc++?