Designated initializers and compound literals for struct in C

Question

I have following struct:

typedef struct my_struct {
    int a;
    int b;
    int *c;
} my_struct;

is:

my_struct n = (my_st         


        

Answer 1

Is my_struct n = (my_struct) { .b = 3 }; equivalent to my_struct n = (my_struct) { .a = 0, .b = 3, .c = NULL };?

Yes. A compound literal may fail to provide full initialization, in which case any unimitialized members initialize to zero (NULL is case of pointer member) by default.

What about my_struct n = (my_struct) { .b = 3, 0 };?

Member b and c will be initialized to 3 and 0 respectively while a will be initialized to 0 by default.