decompiling back to C++?

If you are actually interested in learning about what the structures from c++ to assembly look like, Kris Kaspersky presents very clear and useful information in his book Hacker Disassembling Uncovered.

He presents lots of information about how compilers optimize code and why it would be impossible to write a program to decompile back to c++. IDAs FLIRT signatures are a big step, recognizing the patterns of known api's and displaying them, however even those arn't entirely correct. IDA often misrecognizes calling conventions, I can't imagine relying on a program to transform anything more complex than that if it isn't within reasonable amount of accuracy.