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
– Jonathan Leffler, Commented Jan 11, 2011 at 6:14
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
– Jens Gustedt, Commented Jan 11, 2011 at 7:59

paxdiablo · Accepted Answer · 2011-01-11 05:58:44Z

54

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.

answered Jan 11, 2011 at 5:58

paxdiablo

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Comments

rogerdpack · Accepted Answer · 2018-02-20 18:46:21Z

18

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, 2018 at 18:46

answered Mar 27, 2014 at 19:51

rogerdpack

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3 Comments

stdcerr Over a year ago

In this example, CyclicPrefixType_t is not actuaslly a type but just the name of the enum - so it's a bit different.

Gopi M Over a year ago

if I pass a value which is not in the enum list also received by ' void func ()` and the same value is printed. is it valid behavior ?

rogerdpack Over a year ago

Maybe if 2 enums have the same value? Wouldn't be common... :)

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