source: vendor/glibc-tests/glibc/stdio-common/tstdiomisc.c

#include <float.h>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <wchar.h>

static int
t1 (void)
{
  int n = -1;
  sscanf ("abc  ", "abc %n", &n);
  printf ("t1: count=%d\n", n);

  return n != 5;
}

static int
t2 (void)
{
  int result = 0;
  int n;
  long N;
  int retval;
#define SCAN(INPUT, FORMAT, VAR, EXP_RES, EXP_VAL) \
  VAR = -1; \
  retval = sscanf (INPUT, FORMAT, &VAR); \
  printf ("sscanf (\"%s\", \"%s\", &x) => %d, x = %ld\n", \
          INPUT, FORMAT, retval, (long int) VAR); \
  result |= retval != EXP_RES || VAR != EXP_VAL

  SCAN ("12345", "%ld", N, 1, 12345);
  SCAN ("12345", "%llllld", N, 0, -1);
  SCAN ("12345", "%LLLLLd", N, 0, -1);
  SCAN ("test ", "%*s%n",  n, 0, 4);
  SCAN ("test ", "%2*s%n",  n, 0, -1);
  SCAN ("12 ",   "%l2d",  n, 0, -1);
  SCAN ("12 ",   "%2ld",  N, 1, 12);

  n = -1;
  N = -1;
  retval = sscanf ("1 1", "%d %Z", &n, &N);
  printf ("sscanf (\"1 1\", \"%%d %%Z\", &n, &N) => %d, n = %d, N = %ld\n", \
          retval, n, N); \
  result |= retval != 1 || n != 1 || N != -1;

  return result;
}

static int
F (void)
{
  char buf[20];
  wchar_t wbuf[10];
  int result;

  snprintf (buf, sizeof buf, "%f %F", DBL_MAX * DBL_MAX - DBL_MAX * DBL_MAX,
            DBL_MAX * DBL_MAX - DBL_MAX * DBL_MAX);
  result = strcmp (buf, "nan NAN") != 0;
  printf ("expected \"nan NAN\", got \"%s\"\n", buf);

  snprintf (buf, sizeof buf, "%f %F", DBL_MAX * DBL_MAX, DBL_MAX * DBL_MAX);
  result |= strcmp (buf, "inf INF") != 0;
  printf ("expected \"inf INF\", got \"%s\"\n", buf);

  swprintf (wbuf, sizeof wbuf / sizeof (wbuf[0]), L"%f %F",
            DBL_MAX * DBL_MAX - DBL_MAX * DBL_MAX,
            DBL_MAX * DBL_MAX - DBL_MAX * DBL_MAX);
  result |= wcscmp (wbuf, L"nan NAN") != 0;
  printf ("expected L\"nan NAN\", got L\"%S\"\n", wbuf);

  swprintf (wbuf, sizeof wbuf / sizeof (wbuf[0]), L"%f %F",
            DBL_MAX * DBL_MAX, DBL_MAX * DBL_MAX);
  result |= wcscmp (wbuf, L"inf INF") != 0;
  printf ("expected L\"inf INF\", got L\"%S\"\n", wbuf);

  return result;
}

int
main (int argc, char *argv[])
{
  int result = 0;

  result |= t1 ();
  result |= t2 ();
  result |= F ();

  result |= fflush (stdout) == EOF;

  return result;
}