Dynamic allocation of union of structs - c

Question

I am trying to create a union of 2 structs (dfp and affine) and want to allocate them dynamically. I am getting errors in creating particular struct array inside union. Am I declaring union in right way?
#include <stdio.h>
#include <stdlib.h>
struct{
int fp;
}dfp;
struct{
int scale;
int zp;
}affine;
union{
struct dfp *df;
struct affine *af;
}quant;
struct member{
int total;
union quant arr;
};
int main(void) {
// your code goes here
struct member* ptr;
ptr = (struct member *)malloc(sizeof(struct member));
ptr->total = 2;
int type = 0;
if(!type){
ptr->arr->df = (struct dfp*)malloc(ptr->total*sizeof(struct dfp)); //error
for(int i=0;i<2;i++){
ptr->arr->df->fp[i] = 10;
}
}
else{
ptr->arr->af = (struct affine*)malloc(ptr->total*sizeof(struct affine)); //error
for(int i=0;i<2;i++){
ptr->arr->af->scale[i] = 10;
ptr->arr->af->zp[i] = 20;
}
}
return 0;
}

Answer 1

Most issues have already been pointed out by others separately. This is my attempt at writing a complete answer with explanations and advice.
First off, please check your exact compiler warnings and errors. These are your best help in resolving these kind of issues.
The program does not contain a union of structs, but a union of pointers to structs.
The program's definitions are not correct. Taking dfp as an example. This, struct { int fp; } dfp;, defines an anonymous struct with the the variable name dfp. The name of the struct should go before the struct declaration list, e.g. struct dfp { int fp; };. See here or see the C standard specifications.
Judging by the code in main, the member variables of the structs should be arrays of size 2 instead of single ints.
The operator -> is for "member access using a pointer". Since arr is not a pointer, use a dot (.) to access its members. See here.
Dynamically allocated memory must be free'd, or else the program will have one or more memory leaks.
Here is the full code with all mentioned corrections:
#include <stdio.h>
#include <stdlib.h>
struct dfp {
int fp[2];
};
struct affine {
int scale[2];
int zp[2];
};
union quant {
struct dfp *df;
struct affine *af;
};
struct member {
int total;
union quant arr;
};
int main(void) {
struct member* ptr;
ptr = (struct member *)malloc(sizeof(struct member));
ptr->total = 2;
int type = 0;
if(!type) {
ptr->arr.df = (struct dfp*)malloc(ptr->total*sizeof(struct dfp));
for(int i=0;i<2;i++){
ptr->arr.df->fp[i] = 10;
}
}
else {
ptr->arr.af = (struct affine*)malloc(ptr->total*sizeof(struct affine));
for(int i=0;i<2;i++){
ptr->arr.af->scale[i] = 10;
ptr->arr.af->zp[i] = 20;
}
}
if(!type) {
free(ptr->arr.df);
}
else {
free(ptr->arr.af);
}
free(ptr);
}

Answer 2

Correct the struct definition as below:
struct dfp {
int fp;
};
struct affine{
int scale;
int zp;
};