Accessing unions inside structs

Question

how do i access unions inside structs , from a function other then main
to which i passed the struct as a parameter

Answer 1

OK. This is interesting. A segmentation fault occurred because name and course within your struct is uninitialised. As a result, attempting to write to whatever address name and course is pointing to, will cause the program to throw segfault. For some reason, Code Playground does not show anything.

In order to fix this, you can change the char pointers to stack-allocated arrays instead.

typedef struct{
char name[20];
int enn;
char course[20];
int fee_status;
union {
char* aca[100];
int acn;
}ac_status;
}istu;

Reference: https://stackoverflow.com/questions/13447891/segmentation-fault-using-scanf

Answer 2

Arun Sharma I'm not sure if it is possible to initialize and use an union which is within a struct, without being given an object of the union within the struct.

Your struct can be modified as:

typedef struct {
// other members
typedef union {
// union members
} ac_status;
} istu;

To make it possible to call

istu.ac_status.acn;

Answer 3

Arun Sharma Sorry about the mess up. I was working with C++ instead of C. Check out a working example:

https://code.sololearn.com/cUfhS09buyV6/?ref=app

Answer 4

Let's say your struct is:

struct Test {
union { int mem = 3939; } uObj;
};

and you pass it to a function in main:

Test obj;
access(obj);

The function should be able to access the union member by calling

obj.uObj.mem;

Answer 5

here (the commented part)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct{
char * name;
int enn;
char * course;
int fee_status;
union ac_status{
char* aca[100];
int acn;
};
}istu;

void give_stu_info(istu stu){
printf(" name : %s \n erollment no : %d\n course : %s\n", stu.name, stu.enn, stu.course );
/* if(stu.fee_status == 0){
strcpy(stu.ac_status.aca, "admit_card_available");
printf(" %s", stu.ac_status.aca);
}else{
stu.ac_status.acn = 6006;
printf(" %d", stu.ac_status.acn);
}
*/
}

int main() {

istu arun={"arun_may", 12345678, "HCI", 0};

give_stu_info(arun);

return 0;
}

Answer 6

Hatsy Rei
y r u writing istu(the structure tag) instead of stu
chaining dot operators worked fine with stucts inside structs idk if it works with unions inside structs

Answer 7

also, typedef before union gives error
and u cannot declear values for union members inside the union

Answer 8

hey Hatsy Rei
check this out

https://code.sololearn.com/cZ6776GJp4ow/?ref=app

could u please figure out whats wrong, it's not showing any errors

Answer 9

Hasty Rei
ya, not working
i'll show you
also i meant in c (tag)