prologue of main tldr it doesn't matter

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Code snippets taken from GNU coreutils are under license GPL-3.0

TL;DR: none of these matters unless you want to dig deep into locale and ancient machines. Perhaps the only thing to look at is atexit()

There are a few function calls at the beginning of main, for example cp.c;
(note, what happens between _start and main is per standard library, that’s another story)

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// Copyright (C) 1989-2025 Free Software Foundation, Inc.
// Written by Torbjörn Granlund, David MacKenzie, and Jim Meyering.

int
main (int argc, char **argv)
{
  // [SNIP] .. declare vairables
  initialize_main (&argc, &argv);
  set_program_name (argv[0]);
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

  // some calls this
  atexit (close_stdin);
  // some calls this
  initialize_exit_failure (SOME_ERR_ENUM);

  // [SNIP] .. deal with commandline options
  // [SNIP] .. and rest of the code
}

• initialize_main : macro defined in system.h.. used for OS/2, which calls _wildcard and _response macros, of which I have no idea¹….
• set_program_name, functoin defined in gnulib/lib/progname.{c,h}. Basically storing the program’s calling name (argv[0]) into a global variable (w/ absolute path). Also involves some temporary executable relating libtool…
• setlocale set current locale (man 3 setlocale)

  On  startup  of  the  main  program, the portable "C" locale is selected as
  default.  A program may be made portable to all locales by calling:
  setlocale(LC_ALL, "");
  

• bindtextdomain / textdomain. Also locale related but that’s another story
• atexit: man 3 atexit - register a function to be called at normal process termination
• initialize_exit_failure .. set exit_failure to given status code (on error return)