how does Fiasco achieve C++ support

HI,

My big question is how Fiasco can support C++?
I think in order to build Fiasco, we need some kind of c++
cross-compiler (in this case, it is gcc), this is because we build
Fiasco and its applications on Linux.
But on the other hand, I did not see any special configuration or
modification of gcc when I build Fiasco.
I want to know how Fiasco is build without a cross-compiler.

In particular, I know gcc uses some its internal libraries to support
exception handing, threads/locking and STL in C++. And those libraries
may include libgcc, libstdc++.
But I also do not find that hose libraries are ported to Fiasco.
Without poring those libraries, how to support C++ in Fiasco?
As those libraries may use some lock mechanisms like mutex and C
library functions like malloc, I cannot understand how
Fiasco provides such support (locks, C library) to those libraries.

Thank you very for any help and explanation.
Yuxin