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The output of the compiler is in Execution Executable and Linking Linkable Format (ELF). We use three types of standard ELF files. Unlinked compiler output files are of type Relocatable. The core containing RTEMS and run-time libraries is of type Executable, i.e., the format for main programs. Modules are stored as Shared Object files, i.e., shared library format. ELF has just the single format for both uses: modules loaded explicitly by the application such as Python extension modules as well as for libraries with one memory image shared among multiple processes. In RTEMS there are no processes and there is only one address space for main memory so the "shared" part of "shared object" is irrelevant; we just want the load-on-demand capability. Some platforms such as MacOS X use different file formats for loadable modules and for shared objects so the two are not interchangeable.
A core image and a module both contain a single loadable segment, a piece of data meant to be loaded into a contiguous region of memory. In both cases the segment contains a special nested segment called the "dynamic section" which is used by the dynamic linker to find the dynamic symbol table for the core or module.
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