But I don't understand this logic: When does
!defined(CONFIG_BUILD_KERNEL) && defined(__KERNEL__) happen?
In the build, we build both user space code and internal OS code.
__KERNEL__, if defined means that we are currently building the internal
OS code. That allows the same files to be build differently depending
on if it is inside our outside the OS.
defined(__KERNEL__) means we are build OS internal code
CONFIG_BUILD_KERNEL means that we performing a KERNEL build. In the
KERNEL build, the OS has its own private heap.
!defined(CONFIG_BUILD_KERNEL) means that we are doing a FLAT or a
PROTECTED build.
In the FLAT build there is only one heap. In the PROTECTED build there
is a kernel heap and a user heap. In KERNEL build there is a kernel
heap, and a separate heap for every process that is populated via sbrk().
