The __libc_start_main() function shall perform any necessary initialization of the execution environment, call the main function with appropriate arguments, and handle the return from main(). If the main() function returns, the return value shall be passed to the exit() function.
Note: While this specification is intended to be implementation independent, process and library initialization may include:
This list is an example only.
performing any necessary security checks if the effective user ID is not the same as the real user ID.
initialize the threading subsystem.
registering the rtld_fini to release resources when this dynamic shared object exits (or is unloaded).
registering the fini handler to run at program exit.
calling the initializer function (*init)().
calling main() with appropriate arguments.
calling exit() with the return value from main().
__libc_start_main() is not in the source standard; it is only in the binary standard.
The section on Process Initialization in each of the architecture specific parts of ISO/IEC 23360.