Passing Array as argument to a new thread in C - c

Question

I am attempting to pass an array as an argument to a function in a new thread using pthread_create, is this possible? I have an array of integers and a calculate average method that is called from the create thread method but I cannot seem to pass my array into the method correctly. Here is my code:
int nums[];
int average;
int size = 0;
void *calcAvg(int *nums[]);
int main(int argc, char *argv[]){
/* initialize an array of the integers to be passed */
nums[argc - 1];
for(int i = 0; i < argc - 1; i++){
nums[i] = atoi(argv[i + 1]);
size++;
}
/* Thread Identifier */
pthread_t avgThread;
pthread_create(&avgThread, NULL, calcAvg, nums);
pthread_join(avgThread, NULL);
printf("average= %d", average);
}
void *calcAvg(int *nums[]){
int sum;
for(int i = 0; i < size; i++){
sum += nums[i];
}
average = sum / (size);
pthread_exit(0);
}

Answer 1

there is lots of problem in your code, i fix some to compile
hope it will help
compile: gcc -o main main.c -lpthread
execute: ./main 2 5
output: 3
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
int average;
int size = 0;
void *calcAvg(void *arg);
int main(int argc, char *argv[]){
/* initialize an array of the integers to be passed */
int *nums = (int*)malloc((argc - 1)*sizeof(int));
int i = 1;
for(i = 1; i < argc ; i++){
nums[i-1] = atoi(argv[i]);
size++;
}
/* Thread Identifier */
pthread_t avgThread;
pthread_create(&avgThread, NULL, calcAvg, (void*)nums);
pthread_join(avgThread, NULL);
printf("average = %d \n",average);
free(nums);
}
void *calcAvg(void *arg){
int *val_p = (int *) arg;
int sum = 0;
int i = 0;
for( i = 0; i < size; i++){
sum += val_p[i];
}
average = sum / (size);
pthread_exit(0);
}

Answer 2

Change the following
void *calcAvg(int *nums[]){
int sum;
for(int i = 0; i < size; i++){
sum += nums[i];
}
average = sum / (size);
pthread_exit(0);
}
to
void *calcAvg(void *arg){
int *val_p = (int *) arg;
int sum;
for(int i = 0; i < size; i++){
sum += val_p[i];
}
average = sum / (size);
pthread_exit(0);
}

Answer 3

The main issue that 'pthread_create()' takes a void pointer as its last argument. You are trying to pass to it an array of pointers to integers. Issue "man pthread_create" at the terminal to see the argument types you should be passing.
What you really want to do is just pass the of array integers to the thread. In C, array indexing is just notation for pointer arithmetic. Writing nums[i] is equivalint to &nums[0] + i or just nums+i. The last case works because the name of an array in C can be used as a pointer to the first element of the array.
change void *calcAvg(int *nums[]) to void *calcAvg(void* thread_args). Then in 'calcAvg' write int *nums = (int*)thread_args. Now you can use nums in that function just as if you had called calcAvg(nums), which in in essence you have done.