enum with unsigned char size

[pozz]

Hi all,
I want to use enum in this way:

typedef enum {
FIRST=1,
SECOND,
THIRD,
FORTH,
} order_t;

Now, if I declare a variable such as:
order_t n;
compiler consider n as an integer (2 byte in a 16 bit environment).

If I use only 4 values in an enumeration, n can be a simple unsigned
char, i.e. sizeof(n)=1. Is it possible to use enumeration and to
specify byte-length of that enumeration?

I know that I can write:
typedef enum {
.... (as before)
} order_t;
unsigned char n;

....
n=FIRST;
....

But in that way I lose the link between variable and enumeration.

 

[Jack Klein]

Hi all,
I want to use enum in this way:

typedef enum {
FIRST=1,
SECOND,
THIRD,
FORTH,
} order_t;

Now, if I declare a variable such as:
order_t n;
compiler consider n as an integer (2 byte in a 16 bit environment).

There's a good chance that your compiler offers some option to do
this.

If I use only 4 values in an enumeration, n can be a simple unsigned
char, i.e. sizeof(n)=1. Is it possible to use enumeration and to
specify byte-length of that enumeration?

No standard way. The standard doesn't place any real requirement on
the type used when you define a value of an enumeration type. It is
allowed to use any type which can contain all of the defined values.
So it could decide to use a char or unsigned char, but it is not
required to. And there is no standard way to do what you want.

I know that I can write:
typedef enum {
... (as before)
} order_t;
unsigned char n;

...
n=FIRST;
...

But in that way I lose the link between variable and enumeration.

Again, consult your compiler documentation and see if it offers an
option to do what you want. But even if it does, remember that it's
not standard and not particularly portable.

--
Jack Klein
Home: http://JK-Technology.Com
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[Micah Cowan]

Hi all,
I want to use enum in this way:

typedef enum {
FIRST=1,
SECOND,
THIRD,
FORTH,
} order_t;

Now, if I declare a variable such as:
order_t n;
compiler consider n as an integer (2 byte in a 16 bit environment).

If I use only 4 values in an enumeration, n can be a simple unsigned
char, i.e. sizeof(n)=1. Is it possible to use enumeration and to
specify byte-length of that enumeration?

I know that I can write:
typedef enum {
... (as before)
} order_t;
unsigned char n;

...
n=FIRST;
...

But in that way I lose the link between variable and enumeration.

There is no rael link between them anyway, other then the textual hint
given to the human reader of the source. This could easily be solved
with a comment:

/* order_t n; */
unsigned char n;

HTH,
-Micah