How to pass ENUM as function argument in C

Question

I have an enum declared as:

typedef enum 
{
   NORMAL = 0,           
   EXTENDED              

} CyclicPrefixType_t;

CyclicPrefixType_t cpType;

I need a function that takes this as an argument:

fun(CyclicPrefixType_t cpType);

The function declaration is:

void fun(CyclicPrefixType_t cpType);

How can I fix it? I don't think it is correct.

Why do you think that is incorrect? What did your compiler tell you? — Jonathan Leffler, Jan 11 '11 at 06:14
Don't use typenames with `_t` at the end these are usually reserved, in particular by POSIX. But as the others say, your prototype is ok. — Jens Gustedt, Jan 11 '11 at 07:59

score 48 · Answer 1 · answered Jan 11 '11 at 05:58

That's pretty much exactly how you do it:

#include <stdio.h>

typedef enum {
    NORMAL = 31414,
    EXTENDED
} CyclicPrefixType_t;

void func (CyclicPrefixType_t x) {
    printf ("%d\n", x);
}

int main (void) {
    CyclicPrefixType_t cpType = EXTENDED;
    func (cpType);
    return 0;
}

This outputs the value of EXTENDED (31415 in this case) as expected.

rogerdpack · Answer 2 · 2018-02-20T18:46:21.147

15

The following also works, FWIW (which confuses slightly...)

#include <stdio.h>

enum CyclicPrefixType_t {
    NORMAL = 31414,
    EXTENDED
};

void func (enum CyclicPrefixType_t x) {
    printf ("%d\n", x);
}

int main (void) {
    enum CyclicPrefixType_t cpType = EXTENDED;
    func (cpType);
    return 0;
}

Apparently it's a legacy C thing.

edited Feb 20 '18 at 18:46

answered Mar 27 '14 at 19:51

rogerdpack

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In this example, `CyclicPrefixType_t` is not actuaslly a type but just the name of the `enum` - so it's a bit different. – stdcerr Nov 26 '14 at 19:04

How to pass ENUM as function argument in C

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