I\'m having trouble creating an std::string (or any C++ object, I guess) in GDB. I tried lots of variations to the following and none of them seem to work:
std::string
What do you mean by "creating"? GDB doesn't persist C++ objects (your application does that), so you can't create a C++ object in GDB itself.
However, you should be able to call specific function of your application from GDB.