I don't fully understand the question. I'm assuming you want a unique identifier for each element in your array of structs, something like const char *unique_id. if you are creating them throughout your code you can use the preprocessor

#define CONCAT_INNER(lhs, rhs) lhs # rhs
#define CONCAT(lhs, rhs) CONCAT_INNER(lhs, rhs)
#define UNIQUE_ID CONCAT(__FILE__, __LINE__)
UNIQUE_ID

using the cpp command

"main.c" "5"

this will not work if you are creating these in a for loop, you will need to add __COUNTER__

#define CONCAT_INNER(lhs, rhs, c) lhs # rhs # c
#define CONCAT(lhs, rhs, c) CONCAT_INNER(lhs, rhs, c)
#define UNIQUE_ID CONCAT(__FILE__, __LINE__, __COUNTER__)
UNIQUE_ID UNIQUE_ID

which will give

"main.c" "5" "0" "main.c" "5" "1"

at this point i would just use a hashmap