Question

In C, I can use the preprocessor to convert a enum to its string equivalent.

But is there any clever trick to convert a char* to a enum.

I can use an if statement and a strcmp for each string and return equivalent enum but is there a more elegant way?

Answer 1

Please, don’t do such hackery. You have almost certainly a design flaw.

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EDIT: If you really must do this for some reason I hacked together this. The example should also show it’s usage:

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

/*** BEGIN HACK ***/

#define CREATEENUM(name, first, ...) \
    typedef enum { first = 0, __VA_ARGS__ } name; \
    char name##_s[] = #first ", " #__VA_ARGS__;
#define TOSTR(x) #x
#define TOENUM(name, x) ((name) _toenum(name##_s, x))

long _toenum(char *enum_s, const char *x) {
    long i = 0;
    size_t len = strlen(enum_s);

    char *copy = (char*) malloc(sizeof(char) * (len + 1));
    strncpy(copy, enum_s, len);
    copy[len] = '\0';

    char *saveptr = NULL;
    char *s = strtok_r(copy, ", ", &saveptr);
    do {
        if (strcmp(s, x) == 0) {
            free(copy);
            return i;
        }
        i++;
    } while((s = strtok_r(NULL, ", ", &saveptr)) != NULL);

    free(copy);
    return -1;
}

/*** END HACK ***/

// create enum with the name "super"
CREATEENUM(super,
    COOL,
    AWESOME,
    UBER,
    JON_SKEET
)

int main(int argc, char *argv[]) {
    printf("%d\n", TOENUM(super, "JON_SKEET")); // 3
    printf("%d\n", TOENUM(super, "EXTREME")); // -1 (not found)
    printf("%d\n", TOENUM(super, "COOL")); // 0

    printf("%s\n", TOSTR(AWESOME)); // AWESOME
    return 0;
}