// Test program for platform dependent things like type sizes, endianess, alignment, ...
// See also https://wiki.debian.org/ArchitectureSpecificsMemo.
//
// Todo: Show more environment parameters like the growth direction of the heap,
// alignment and representation, page sizes, bit padding etc..
// And a preprocessor version with preprocessor output, like
// #if INT_MAX == 0x7fff
// #  warning "INT_MAX is 0x7fff"
// #elif INT_MAX == 0x7fffffff
// #  warning "INT_MAX is 0x7fffffff"
// This is usefull for a) Cross-Compiling and b) checking for freestanding implementations without printf.

// Dr. Rolf Freitag 2020-02-08

#include <stdio.h>
#include <stdint.h>
#include <limits.h>
#include <wchar.h>
#include <alloca.h>
#include <endian.h>
#include <stddef.h>
#include <time.h>

/* Estimate the main endianess.
void endianess ()
{
  union
  {
    uint64_t uli;
    uint32_t ui[2];
    uint16_t usi[4];
    uint8_t uc[8];
  } u_end =
  {
  1};
  printf ("Endianess: ");
  if (1 == u_end.uc[0])
  {
    printf ("LITTLE_ENDIAN\n");
    return;
  }
  else
  {
    if (1 == u_end.usi[1])
    {
      printf ("PDP_ENDIAN\n");
      return;
    }
    else
    {
      if (1 == u_end.uc[7])
      {
        printf ("BIG_ENDIAN\n");
        return;
      }
    }
  }
  printf ("UNKNOWN_ENDIAN\n");
  return;
}
*/

static void
test_size_align (const char *name, size_t size, size_t align)
{
  printf ("sizeof(%s) = %zu\n", name, size);
  if (size != align)
    printf ("alignment(%s) = %zu\n", name, align);
  return;
}

#define TEST_SIZE_ALIGN(type, name) \
  struct test_align_##name { char a; type b; }; \
  test_size_align(#type, sizeof(type), offsetof(struct test_align_##name, b))

static void
test_endian (void)
{
#if __BYTE_ORDER == __LITTLE_ENDIAN
  printf ("byte order = little endian\n");
#elif __BYTE_ORDER == __BIG_ENDIAN
  printf ("byte order = big endian\n");
#else
  printf ("byte order = mybe pdp endian\n");
#endif
  return;
}

static void
test_char (void)
{
  if ((int) (char) -1 == -1)
    printf ("char signedness = signed\n");
  else if ((int) (char) -1 == 255)
    printf ("char signedness = unsigned\n");
  return;
}

static void
test_int (void)
{
  if ((int)(-1) < 0)
    printf ("int signedness = signed\n");
  else
    printf ("char signedness = unsigned\n");
  return;
}

static void
test_stack (void)
{
  void *a = alloca (8);
  void *b = alloca (8);
  if (a > b)
    printf ("stack = grows down\n");
  else
    printf ("stack = grows up\n");
  return;
}

int
main ()
{
  printf ("Size of byte in bits is %d.\n", CHAR_BIT);
  printf("maximum number of bytes in a multibyte character, MB_LEN_MAX = %d\n", MB_LEN_MAX);
  printf ("Size of char (in bytes) is %lu.\n", sizeof (char));
  printf ("Size of wide char is %lu.\n", sizeof (wchar_t));
  printf ("Size of time_t is %lu, time_t is %s.\n", sizeof(time_t), ((time_t)(-1) < 0)? "signed" : "unsigned");
  
  TEST_SIZE_ALIGN (short, short);
  TEST_SIZE_ALIGN (int, int);
  TEST_SIZE_ALIGN (long, long);
  TEST_SIZE_ALIGN (long long, long_long);
  TEST_SIZE_ALIGN (float, float);
  TEST_SIZE_ALIGN (double, double);
  TEST_SIZE_ALIGN (long double, long_double);
  TEST_SIZE_ALIGN (void *, pointer);
  TEST_SIZE_ALIGN (size_t, size_t);
  test_endian ();
  test_char ();
  test_int ();
  test_stack ();

  return 0;
}