If I compile a program with gcc's c++ compiler does that mean that the compiled executables and object code are GPL, ie not allowed to be sold or given propriety?
Or does the GPL rule only apply to modifications of the gcc itself, rather than the compiled programs it is capable of producing?
Nobody anywhere can claim propriety over your work because you used their tool in its creation.
The GPL applies to modifications of existing software --in this case, the GCC: you can do (nearly) anything you like to the GCC except copyright it, sell it, or obfuscate its source code. (That's a very simplified version.)
Because of licensing concerns like yours, the GCC's C runtime and other objects that get linked into your executable are licensed such that your code is not "contaminated" with the GPL --you retain full control over your creation.