Is there a standard C header file which assigns a numeric value to all of the primitive types?

Question

I have some code which performs differently depending on the underlying data type. EG:

void *some_data = obtain_data();
int data_type = obtain_data_type();
         


        

Answer 1

There are no such standard constants, no. There's a lot of things in C that you'd think would be standardized, but aren't.

---

As a side note, you could take the first steps towards a bit more modern C programming by using the C11 _Generic keyword and implementing polymorphism behavior instead of using run-time checking of such enums. In fact, you can get rid of the enum entirely:

// variant.h / variant.c
#include <stdio.h>

typedef void print_func_t (const void* data);

typedef struct
{
  void* data;
  print_func_t* print;
} variant_t;


void print_char  (const void* data) { printf("%c",  *(const char*)  data); }
void print_short (const void* data) { printf("%hd", *(const short*) data); }
void print_int   (const void* data) { printf("%d",  *(const int*)   data); }

void print (const variant_t* var)
{
  var->print(var->data);
}

#define variant_init(var) { \
  .data = &var, \
  .print = _Generic((var), char: print_char, short: print_short, int: print_int) \
}

Caller:

int main() 
{
  char c = 'A';
  short s = 3;
  int i = 5;

  variant_t var[3] =
  {
    variant_init(c),
    variant_init(s),
    variant_init(i)
  };

  for(size_t i=0; i<3; i++)
  {
    print(&var[i]);
    printf(" ");
  }

  return 0;
}

Answer 2

This is called in C++ a variant type. There are many libraries that do this for you, such as:

1. QVariant from Qt
2. Boost any

But remember that there's a price to pay when using such a library. Things are not most efficient when you use variants, but some times it's necessary, such as when you use OPC/UA protocols.