How does the c compiler execute when we include a pointer declaration to a structure which we haven't finished defining yet?

Question

struct noderecord {
    struct noderecord* next;
    int data;
}; 

how is the pointer next declared without some error? we have added one more element subsequently after declaring a pointer, wouldn't the pointer element be of the wrong size?

Answer 1

All pointers to structures in a C implementation are the same size as each other, per C 2018 6.2.6.1 28:

… All pointers to structure types shall have the same representation and alignment requirements as each other…

So, to know how big a pointer to a structure is, the compiler does not need to know anything about the structure, just that the pointer is pointing to some type of structure.