FBL is the Fuchsia Base Library, which is shared between kernel and userspace. As a result, FBL has very strict dependencies. For example, FBL cannot depend on the syscall interface because the syscall interface is not available within the kernel. Similarly, FBL cannot depend on C library features that are not available in the kernel.
NOTE: Some FBL interfaces below that overlap with standard C++ library interfaces will probably be either removed entirely or made kernel-only (and perhaps renamed inside the kernel) once userspace code has migrated to using standard C++ library facilities where appropriate.
FBL has strict controls on memory allocation. Memory allocation should be explicit, using an AllocChecker to let clients recover from allocation failures. In some cases, implicit memory allocation is permitted, but functions that implicitly allocate memory must be #ifdef'ed to be unavailable in the kernel.
FBL not available outside the Platform Source Tree.