Probably no big trouble (because GCC 4.1 & soon released GCC 4.8 produces compatible code), at least for C code.
For C++ code I believe there is a incompatibility. Certainly the libstdc++
is tied to the compiler version. Sometimes it may be compatible in practice, sometimes not (but the C++ ABI slightly changed too). And this incompatibility may spread to every C++ library.
I believe you should try. If you recompile -with the same newest GCC- all the C++ dependencies, you'll probably be quite safe. So you could compile the newest GCC, then compile folly
and all its dependencies with it.
BTW, I would suggest going to the latest GCC (today 4.7, in a few weeks 4.8).