Question

Is there a possibility to convert enumerator names to string in C?

Answer 1

One way, making the preprocessor do the work. It also ensures your enums and strings are in sync.

#define FOREACH_FRUIT(FRUIT) \
        FRUIT(apple)   \
        FRUIT(orange)  \
        FRUIT(grape)   \
        FRUIT(banana)  \

#define GENERATE_ENUM(ENUM) ENUM,
#define GENERATE_STRING(STRING) #STRING,

enum FRUIT_ENUM {
    FOREACH_FRUIT(GENERATE_ENUM)
};

static const char *FRUIT_STRING[] = {
    FOREACH_FRUIT(GENERATE_STRING)
};

After the preprocessor gets done, you’ll have:

enum FRUIT_ENUM {
    apple, orange, grape, banana,
};

static const char *FRUIT_STRING[] = {
    "apple", "orange", "grape", "banana",
};

Then you could do something like:

printf("enum apple as a string: %s\n",FRUIT_STRING[apple]);

If the use case is literally just printing the enum name, add the following macros:

#define str(x) #x
#define xstr(x) str(x)

Then do:

printf("enum apple as a string: %s\n", xstr(apple));

In this case, it may seem like the two-level macro is superfluous, however, due to how stringification works in C, it is necessary in some cases. For example, let’s say we want to use a #define with an enum:

#define foo apple

int main() {
    printf("%s\n", str(foo));
    printf("%s\n", xstr(foo));
}

The output would be:

foo
apple

This is because str will stringify the input foo rather than expand it to be apple. By using xstr the macro expansion is done first, then that result is stringified.

See Stringification for more information.