libgcc1-test.c

gcc库的原代码,对编程有很大帮助.

/* This small function uses all the arithmetic operators that
   libgcc1.c can handle.  If you can link it, then
   you have provided replacements for all the libgcc1.c functions that
   your target machine needs.  */

int foo ();
double dfoo ();

/* We don't want __main here because that can drag in atexit (among other
   things) which won't necessarily exist yet.  */

main_without__main ()
{
  int a = foo (), b = foo ();
  unsigned int au = foo (), bu = foo ();
  float af = dfoo (), bf = dfoo ();
  double ad = dfoo (), bd = dfoo ();

  discard (a * b);
  discard (a / b);
  discard (a % b);

  discard (au / bu);
  discard (au % bu);

  discard (a >> b);
  discard (a << b);

  discard (au >> bu);
  discard (au << bu);

  ddiscard (ad + bd);
  ddiscard (ad - bd);
  ddiscard (ad * bd);
  ddiscard (ad / bd);
  ddiscard (-ad);

  ddiscard (af + bf);
  ddiscard (af - bf);
  ddiscard (af * bf);
  ddiscard (af / bf);
  ddiscard (-af);

  discard ((int) ad);
  discard ((int) af);

  ddiscard ((double) a);
  ddiscard ((float) a);
  ddiscard ((float) ad);

  discard (ad == bd);
  discard (ad < bd);
  discard (ad > bd);
  discard (ad != bd);
  discard (ad <= bd);
  discard (ad >= bd);

  discard (af == bf);
  discard (af < bf);
  discard (af > bf);
  discard (af != bf);
  discard (af <= bf);
  discard (af >= bf);

  return 0;
}

discard (x)
     int x;
{}

ddiscard (x)
     double x;
{}

foo ()
{
  static int table[] = {20, 69, 4, 12};
  static int idx;

  return table[idx++];
}

double
dfoo ()
{
  static double table[] = {20.4, 69.96, 4.4, 202.202};
  static int idx;

  return table[idx++];
}

/* Provide functions that some versions of the linker use to default
   the start address if -e symbol is not used, to avoid the warning
   message saying the start address is defaulted.  */
extern void start() __asm__("start");
extern void _start() __asm__("_start");

void start() {}
void _start() {}