Memory location of enum value in C

Question

I think I've read somewhere that it is illegal to take the address of an enum value in C (enum values not being lvalues; however, I can't find any information on this now). Is that correct and, if so, why?

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Edit:

Here's an example that clarifies what I mean by "enum value" above. I mean taking the address of first_value below, not taking the address of an actual instance of an enum:

enum myenum
{
    first_value,
    second_value
};

Answer 1

if you have:

enum E {
    X, Y, Z
};

then you cannot take the addresses of X, Y or Z, any more than you can take the addresses of 0, 1 or 2.

However, you can take the address of an enum instance:

typedef enum  {
   X, Y, Z
} E;

int main() {
  E e;
  E * ep;
  ep = & e;
}

Answer 2

The value names for enums are just constant aliases for integers, so it's meaningless to try to take their address. You can take the address of an enum variable just fine, of course.

Answer 3

"Enum value" is slightly ambiguous; however, I assume you mean the following:

enum myenum
{
    first_value,
    second_value
};

In this case, it is illegal to take the address of first_value. The reason for this is that first_value does not actually exist in memory anywhere... it is just a constant, effectively another name for the number 0 (of which, of course, you also cannot take the address).

If, on the other hand, you mean whether you can take the address of a variable that is declared as an enum:

enum myenum x;
enum myenum *mypointer=&x;

then that is definitely possible.

Answer 4

As far as I remember enums in C are just integers. So it would be like pointing to local variable.

Answer 5

Enums are used to replace #define chains:

#define SUCCESS 0
#define LITTLE_ERROR 1
#define BIG_ERROR 2

This can be replaced with:

enum
{
    SUCCESS,
    LITTLE_ERROR,
    BIG_ERROR
};

An enum value such as SUCCESS is merely a symbol for an integer constant, which won't be stored anywhere in the program's memory. Thus it doesn't make sense to take its address.

Answer 6

pls refer the example below:

enum { FIRST,SECOND }var;

here the FIRST and SECOND are constant macros.Hence '&' operator will not work, since it is not stored anywhere in the memory

But for 'var' a memory location will be assigned and the '&' operator can be used.