Declare struct and struct-size related arrays - c

Question

I'm working in a condition like this:
typedef struct __type_x{
sub_type_a a;
sub_type_b b;
sub_type_c c;
}type_x_t;
uint32_t type_x_uids[] = {
1, //a's_uid
2, //b's_uid
3, //c's_uid
};
uint32_t type_x_uid_another[] = {
3, //a's uid in another API system
1, //b's uid in another API system
2, //c's uid in another API system
};
uint32_t type_x_uids_one_more[] = {
1, //a's_uid in yet another system
3, //b's_uid in yet another system
2, //c's_uid in yet another system
};
The problem is: If I need to add one more data(like d) into struct type_x_t, I need to add its uids into all other three arrays.
It is hard to maintain the code.
So I'm wondering if it is possible to maintain all these data from four places into one table?
I can put three uint32 arrays into one 2D array
uint32_t uid[system_id][value];
but I also have to maintain two pieces of code instead of one.
I'm wondering if there is anyway I can move forward? Therefore I can maintain one table to manage all these data. Such like
{#data_type, #data_name, #uid_1, #uid2, #uid 3},
Trying to use Macro to solve the problem, but I cannot access the data in certain position by __VA_ARGS__.

Answer 1

First of all, if you have placed the code adjacently in one single file, you are actually maintaining one place and not several. What you have is not necessarily bad. Anyway...
I will assume there's a reason why type_x_t is a struct and not an array. Then clearly the best design is to add the "uid" for "a" to the sub_type_a struct, or alternatively make a new struct containing both, since those data belong together.
If that's not an option, you could go with the array and then put that inside the type_x_t struct.
If that's not an option either, consider some completely different program design.
With all program design options exhausted, then - and only then - you could consider macros. What you are fishing for is so-called "X macros", which is the last resort and not really recommended, since they make the code much harder to read. The purpose of X macros is to centralize code maintenance of data to one place. It goes like this:
#include <stdint.h>
#define TYPE_X_LIST \
X(a,1,3,1) \
X(b,2,1,3) \
X(c,3,2,2)
typedef struct
{
#define X(name, dummmy1, dummy2, dummy3) sub_type_##name name;
TYPE_X_LIST
#undef X
} type_x_t;
uint32_t type_x_uids[] = {
#define X(dummy1, id, dummy2, dummy3) id,
TYPE_X_LIST
#undef X
};
uint32_t type_x_uid_another[] = {
#define X(dummy1, dummy2, id, dummy3) id,
TYPE_X_LIST
#undef X
};
uint32_t type_x_uids_one_more[] = {
#define X(dummy1, dummy2, dummy3, id) id,
TYPE_X_LIST
#undef X
};
Now you only have to change the "TYPE_X_LIST" when you need to change the data. If you want to keep track of how many data sets you have, you can add an enum to count them:
typedef enum
{
#define X(name, ...) something_##name,
TYPE_X_LIST
#undef X
TYPE_X_N // the number of data sets
} type_x_size_t;
Then TYPE_X_N could be used to set array sizes etc.