Can I display the value of an enum with printf()?

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Is there a one-liner that lets me output the current value of an enum?

7 Answers

As a string, no. As an integer, %d.

Unless you count:

static char* enumStrings[] = { /* filler 0's to get to the first value, */
                               "enum0", "enum1", 
                               /* filler for hole in the middle: ,0 */
                               "enum2", "enum3", .... };

...

printf("The value is %s\n", enumStrings[thevalue]);

This won't work for something like an enum of bit masks. At that point, you need a hash table or some other more elaborate data structure.

enum MyEnum
{  A_ENUM_VALUE=0,
   B_ENUM_VALUE,
   C_ENUM_VALUE
};


int main()
{
 printf("My enum Value : %d\n", (int)C_ENUM_VALUE);
 return 0;
}

You have just to cast enum to int !
Output : My enum Value : 2

The correct answer to this has already been given: no, you can't give the name of an enum, only it's value.

Nevertheless, just for fun, this will give you an enum and a lookup-table all in one and give you a means of printing it by name:

main.c:

#include "Enum.h"

CreateEnum(
        EnumerationName,
        ENUMValue1,
        ENUMValue2,
        ENUMValue3);

int main(void)
{
    int i;
    EnumerationName EnumInstance = ENUMValue1;

    /* Prints "ENUMValue1" */
    PrintEnumValue(EnumerationName, EnumInstance);

    /* Prints:
     * ENUMValue1
     * ENUMValue2
     * ENUMValue3
     */
    for (i=0;i<3;i++)
    {
        PrintEnumValue(EnumerationName, i);
    }
    return 0;
}

Enum.h:

#include <stdio.h>
#include <string.h>

#ifdef NDEBUG
#define CreateEnum(name,...) \
    typedef enum \
    { \
        __VA_ARGS__ \
    } name;
#define PrintEnumValue(name,value)
#else
#define CreateEnum(name,...) \
    typedef enum \
    { \
        __VA_ARGS__ \
    } name; \
    const char Lookup##name[] = \
        #__VA_ARGS__;
#define PrintEnumValue(name, value) print_enum_value(Lookup##name, value)
void print_enum_value(const char *lookup, int value);
#endif

Enum.c

#include "Enum.h"

#ifndef NDEBUG
void print_enum_value(const char *lookup, int value)
{
    char *lookup_copy;
    int lookup_length;
    char *pch;

    lookup_length = strlen(lookup);
    lookup_copy = malloc((1+lookup_length)*sizeof(char));
    strcpy(lookup_copy, lookup);

    pch = strtok(lookup_copy," ,");
    while (pch != NULL)
    {
        if (value == 0)
        {
            printf("%s\n",pch);
            break;
        }
        else
        {
            pch = strtok(NULL, " ,.-");
            value--;
        }
    }

    free(lookup_copy);
}
#endif

Disclaimer: don't do this.

enum A { foo, bar } a;
a = foo;
printf( "%d", a );   // see comments below

Printing an enum value can be tricky as the sizes of each of its members can vary depending on the implementation. Take this example compiled on gcc 8.4.0.

#include <stdio.h>

int main(void) {
  enum option {A = 0, B = 0x100000000};

  // Enumerator sizes of the same enumeration can differ
  printf("sizeof(A)=%zu\n", sizeof(A)); // sizeof(A)=4
  printf("sizeof(B)=%zu\n", sizeof(B)); // sizeof(B)=8

  // Same output even though they have different values
  printf("A=%d\n", A); // A=0
  printf("B=%d\n", B); // B=0

  // You should know beforehand the maximum enumerator size
  printf("A=%ld\n", A); // A=0
  printf("B=%ld\n", B); // B=4294967296
}

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