Creating a C Library: Difference between revisions

= Program Initialization =

The first and most important thing to implement in a C library is the _start function, to which control is passed from your program loader. It's task is to initialize and run the process. Normally this is done by initializing the C library (if needed), then calling the global constructors, and finally calling exit(main(argc, argv)). You can change the name of the default program entry point by adding ENTRY=_my_start_name in your OS-specific binutils emulparams script (binutils/ld/emulparams). You can change which start files are used by modifying gcc/gcc/config/myos.h in your OS-specific GCC. The macros STARTFILE_SPEC and ENDFILE_SPEC define the object files to use in the GCC spec language. See gcc/gcc/config/gnu-user.h for examples on how to use this. If you decide to use the conventional (GNU-like) names and semantics for these initialization files, the following information applies:

popq %rbp

ret

.section .fini

popq %rbp

ret

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