mes/doc/examples/main.c

/* -*-comment-start: "//";comment-end:""-*-
 * Mes --- Maxwell Equations of Software
 * Copyright © 2016,2017 Jan Nieuwenhuizen <janneke@gnu.org>
 *
 * This file is part of Mes.
 *
 * Mes is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or (at
 * your option) any later version.
 *
 * Mes is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Mes.  If not, see <http://www.gnu.org/licenses/>.
 */

#if __GNUC__
void
exit (int code)
{
  asm (
       "movl %0,%%ebx\n\t"
       "movl $1,%%eax\n\t"
       "int  $0x80"
       : // no outputs "=" (r)
       : "" (code)
       );
  // not reached
  exit (0);
}

void
write (int fd, char const* s, int n)
{
  int r;
  //syscall (SYS_write, fd, s, n));
  asm (
       "mov %0,%%ebx\n\t"
       "mov %1,%%ecx\n\t"
       "mov %2,%%edx\n\t"

       "mov $0x4, %%eax\n\t"
       "int $0x80\n\t"
       : // no outputs "=" (r)
       : "" (fd), "" (s), "" (n)
       : "eax", "ebx", "ecx", "edx"
       );
}

#define STDOUT 1

typedef long size_t;
size_t
strlen (char const* s)
{
  int i = 0;
  while (s[i]) i++;
  return i;
}

int
puts (char const* s)
{
  //write (STDOUT, s, strlen (s));
  //int i = write (STDOUT, s, strlen (s));
  int i = strlen (s);
  write (1, s, i);
  return 0;
}

int
strcmp (char const* a, char const* b)
{
  while (*a && *b && *a == *b) {a++;b++;}
  return *a - *b;
}
#endif

int
//main ()
main (int argc, char *argv[])
{
  puts ("Hi Mes!\n");
  if (argc > 1 && !strcmp (argv[1], "--help")) return puts ("argc > 1 && --help\n");
  return 42;
}

#if __GNUC__
void
_start ()
{
  // int r=main ();
  // exit (r);
  int r;
  asm (
       "mov %%ebp,%%eax\n\t"
       "addl $8,%%eax\n\t"
       "push %%eax\n\t"

       "mov %%ebp,%%eax\n\t"
       "addl $4,%%eax\n\t"
       "movzbl (%%eax),%%eax\n\t"
       "push %%eax\n\t"

       "call main\n\t"
       "movl %%eax,%0\n\t"
       : "=r" (r)
       : //no inputs "" (&main)
       );
  exit (r);
}
#endif