source: vendor/glibc-tests/glibc/string/tst-strlen.c

/* Make sure we don't test the optimized inline functions if we want to
   test the real implementation.  */
#undef __USE_STRING_INLINES

#include <stdio.h>
#include <string.h>

int
main(int argc, char *argv[])
{
  static const size_t lens[] = { 0, 1, 0, 2, 0, 1, 0, 3,
                                 0, 1, 0, 2, 0, 1, 0, 4 };
  char basebuf[24 + 32];
  size_t base;

  for (base = 0; base < 32; ++base)
    {
      char *buf = basebuf + base;
      size_t words;

      for (words = 0; words < 4; ++words)
        {
          size_t last;
          memset (buf, 'a', words * 4);

          for (last = 0; last < 16; ++last)
            {
              buf[words * 4 + 0] = (last & 1) != 0 ? 'b' : '\0';
              buf[words * 4 + 1] = (last & 2) != 0 ? 'c' : '\0';
              buf[words * 4 + 2] = (last & 4) != 0 ? 'd' : '\0';
              buf[words * 4 + 3] = (last & 8) != 0 ? 'e' : '\0';
              buf[words * 4 + 4] = '\0';

              if (strlen (buf) != words * 4 + lens[last]
                  || strnlen (buf, -1) != words * 4 + lens[last])
                {
                  printf ("failed for base=%Zu, words=%Zu, and last=%Zu\n",
                          base, words, last);
                  return 1;
                }
            }
        }
    }
  return 0;
}