gnu C, value to string, preprocessor magic

Question

Friend, there are a lots of enum values

enum{
ABC = 123,
XYZ = 456,
FOO = 4321,
BAR = 98743,
...
}

when I got the value, I want print the enum's NAME. we could create a string , value pair array. but have to repeat literally the enum body. if enum changed, then array has to be changed accordingly. I remember preprocess could do magic, create enum list, also generate string, value array with one body.

hope masters here could give me a guide.

thanks Xian

score 2 · Answer 1 · answered Mar 20 '21 at 23:49

In my_enum.inc:

MY_ENUM_ITEM(ABC, 123)
MY_ENUM_ITEM(XYZ, 456)
MY_ENUM_ITEM(FOO, 4321)
MY_ENUM_ITEM(BAR, 98743)

Then to define the enum itself use something like:

enum my_enum {
#define MY_ENUM_ITEM(_n, _v) _n = _v,
#include "my_enum.inc"
#undef MY_ENUM_ITEM
};

and to convert from a value to a string:

const char *my_enum_to_string(enum my_enum e) {
    switch (e) {
#define MY_ENUM_ITEM(_n, _v) case _v: return #_n;
#include "my_enum.inc"
#undef MY_ENUM_ITEM
    default: return NULL;
    }
}

Wow, you are genius! worked great. thanks – Xianwu Luo Mar 21 '21 at 01:27 — Xianwu Luo, Mar 21 '21 at 01:27

score 0 · Answer 2 · answered Mar 20 '21 at 23:43

0

Why not use a hashmap, instead of using the C preprocessor?

answered Mar 20 '21 at 23:43

chutsu

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hashmap is kind of overkill. yes, it is an options. – Xianwu Luo Mar 20 '21 at 23:56

gnu C, value to string, preprocessor magic

2 Answers2