This folder contains all of the header files for the Smile interpreter. Some of these are designed to be included externally, and some are not. As a general rule, anything with the name internal is designed to be only used inside the interpreter, and should not be used outside.
All of the header files are wrapped with safe #ifdef/define __HEADER_H__ blocks, so they can be included multiple times.
Note that the headers for the Boehm garbage collector and Intel decimal math library are kept outside of here, in their original source trees, but they are referenced by other #includes in here. To access the Boehm GC, you can simply include gc.h, and to access the decimal numerics, you only need to pull in numeric/real.h.