SLAA534A June 2013 – June 2020
A static variable that has an initial non-zero value should be allocated into an initialized data section. The section's contents should be an image of the contents of memory corresponding to the initial values of all variables in the section. The variables thus obtain their initial values directly as the section is loaded into memory. This is the so-called direct initialization model used by most ELF-based toolchains.
Variables that are expected to be initialized to zero can be allocated into uninitialized sections. The loader is responsible for zeroing uninitialized space at the end of a data segment.
Although the compiler is required to encode initialized variables directly, the linker is not. The linker may translate the directly encoded initialized sections in the object files into an encoded format for the executable file, and rely on a library function to decode the information and perform the initialization at program startup. (Recall that the linker may assume that the library is from the same toolchain.) Encoding initialization data helps save space in the executable file; it also provides an initialization mechanism for self-booting ROM-based systems that do not rely on a loader. The TI toolchain implements such a mechanism, described in Chapter 14. Other toolchains may adopt a compatible mechanism, a different mechanism, or none at all.