C- Iterating over an array of structs passed through a void* - c

Question

I have a function
struct Analysis reduce (int n, void* results)
Where n is the number of files to be analyzed, and I'm passing an array of Analysis structs to results.
The Analysis struct is defined as follows:
struct Analysis {
int ascii[128]; //frequency of ascii characters in the file
int lineLength; //longest line in the file
int lineNum; //line number of longest line
char* filename;
}
I've cast the void * as such,
struct Analysis resArray[n];
struct Analysis* ptr = results;
resArray[0] = ptr[0];
but I can't figure out how to iterate through the resArray properly. I've tried
for (i = 0; i < n; i++){
printf("lineLength: %d\n", resArray[i].lineLength);
}
with n = 3, and I'm getting garbage values. resArray[0] is correct, but resArray[1] is an insanely high number and resArray[2] is just 0. Why wouldn't resArray[1] or resArray[2] give the correct values? If I was incrementing the address incorrectly then it would make sense but I'm just accessing the array at a certain index. Pretty lost here!

Answer 1

resArray[0] is correct because there is "something":
resArray[0] = ptr[0];
Other elements are garbage because you didn't set there any values. If you want to copy entire array you need to change copying method to:
for (i = 0; i < n; i++)
{
resArray[i] = ptr[i];
}

Answer 2

You can't assign a pointer to an array directly because they are different typessince array[n] is type struct analysis(*)[n] and ptr is type struct analysis(*). Check here for more info.

Answer 3

Hopefully this code will help you.
#include <stdio.h>
#define d 3
struct Analysis {
int ascii[128];
int lineLength;
int lineNum;
char *filename;
};
struct Analysis Analyses[d];
struct Analysis reduce(int n, void *results) {
struct Analysis resArray[n];
struct Analysis *ptr = results;
for (int i = 0; i < n; i++) {
resArray[i] = ptr[i];
}
for (int i = 0; i < n; i++) {
printf("lineLength: %d\n", ptr[i].lineLength);
}
return *ptr;
}
int main(void) {
struct Analysis a = {{5}, 2, 2, "George"};
struct Analysis b = {{6}, 3, 3, "Peter"};
struct Analysis c = {{7}, 4, 4, "Jane"};
Analyses[0] = a;
Analyses[1] = b;
Analyses[2] = c;
reduce(d, &Analyses);
return 0;
}
You can try it online.