Fix gcc warnings with _Generic macro and compound literals

I have a struct with a union and an enum of its kind in it. I've made a macro that outputs a compound literal of the struct, that sets the kind and the data of the union according to the type passed to the macro use _Generic.

Example code:

#include <stdio.h>struct mystruct {    enum { K_NUM, K_STR } kind;    union { int num; char * str; };};#define MYSTRUCT(X) _Generic((X), \    int: (struct mystruct){K_NUM, .num=X}, \    char *: (struct mystruct){K_STR, .str=X} \)void print_mystruct(struct mystruct s) {    switch (s.kind) {    case K_NUM: printf("mystruct (num): %d\n", s.num); break;    case K_STR: printf("mystruct (str): %s\n", s.str); break;    }}int main() {    print_mystruct(MYSTRUCT(2));    print_mystruct(MYSTRUCT("test"));}

It does compile with gcc, and then running it correctly outputs:

mystruct (num): 2mystruct (str): test

But I get all these compile warnings:

c.c: In function 'main':c.c:21:26: warning: initialization of 'char *' from 'int' makes pointer from integer without a cast [-Wint-conversion]   21 |  print_mystruct(MYSTRUCT(2));      |                          ^c.c:10:40: note: in definition of macro 'MYSTRUCT'   10 |  char *: (struct mystruct){K_STR, .str=X} \      |                                        ^c.c:21:26: note: (near initialization for '(anonymous).<anonymous>.str')   21 |  print_mystruct(MYSTRUCT(2));      |                          ^c.c:10:40: note: in definition of macro 'MYSTRUCT'   10 |  char *: (struct mystruct){K_STR, .str=X} \      |                                        ^c.c:22:26: warning: initialization of 'int' from 'char *' makes integer from pointer without a cast [-Wint-conversion]   22 |  print_mystruct(MYSTRUCT("test"));      |                          ^~~~~~c.c:9:37: note: in definition of macro 'MYSTRUCT'    9 |  int: (struct mystruct){K_NUM, .num=X}, \      |                                     ^c.c:22:26: note: (near initialization for '(anonymous).<anonymous>.num')   22 |  print_mystruct(MYSTRUCT("test"));      |                          ^~~~~~c.c:9:37: note: in definition of macro 'MYSTRUCT'    9 |  int: (struct mystruct){K_NUM, .num=X}, \      |                                     ^

I tried casts in the compound literals like so:

int: (struct mystruct){K_NUM, .num=(int)X}, \char *: (struct mystruct){K_STR, .str=(char *)X} \

But I get different warnings:

c.c: In function 'main':c.c:9:37: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]    9 |  int: (struct mystruct){K_NUM, .num=(int)X}, \      |                                     ^c.c:22:17: note: in expansion of macro 'MYSTRUCT'   22 |  print_mystruct(MYSTRUCT("test"));      |                 ^~~~~~~~