Polish notation sizeof()

of_size.c

#include <stdint.h>
#include <stdio.h>

/** Polish notation sizeof(). */
#define of_size(x) __typeof__( \
  _Generic((x)                 \
  ,      int: of_signed   (x)  \
  , unsigned: of_unsigned (x)) )
				
#define of_signed(x)           \
  _Generic(&(char[(x)]){0}     \
  , char (*)[ 1]: (  int8_t) 0 \
  , char (*)[ 2]: ( int16_t) 0 \
  , char (*)[ 4]: ( int32_t) 0 \
  , char (*)[ 8]: ( int64_t) 0 )

#define of_unsigned(x)         \
  _Generic(&(char[(x)+5u]){0}  \
  , char (*)[ 6]: ( uint8_t) 0 \
  , char (*)[ 7]: (uint16_t) 0 \
  , char (*)[ 9]: (uint32_t) 0 \
  , char (*)[13]: (uint64_t) 0 )

#define info(x)                \
  printf("%-3s%6d, %zu B\n",#x \
         , (int)(x), sizeof(x))

int main (void)
{
	of_size(1)  i8  = -1;
	of_size(1u) u8  = -1;

	of_size(2)  i16 = -1;
	of_size(2u) u16 = -1;

	info(i8);  //    -1, 1 B
	info(u8);  //   255, 1 B

	info(i16); //    -1, 2 B
	info(u16); // 65535, 2 B
}