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Occasionally I run into some strange pre-processor code with a list like this: #define LIST \ X(1) \ X(2) \ X(3) \ And then code followed by other obscure macros and ...
#1: Initial revision
by
Lundin
·
2025-02-25T15:07:22Z (3 days ago)
What are X macros and when to use them?
Occasionally I run into some strange pre-processor code with a list like this:
```c
#define LIST \
X(1) \
X(2) \
X(3) \
```
And then code followed by other obscure macros and macro calls like:
```c
typedef enum
{
#define X(n) ITEM_##n,
LIST
#undef X
} list_t;
```
These are apparently referred to as [X macros](https://en.wikipedia.org/wiki/X_macro). The Wikipedia page is bleak when it comes to describing what these are acutally good for.
What are X-macros good for and when should they be used? Which style is preferred? What are the advantages and disadvantages?