How to create n threads, each one creates n - 1 threads - c

Question

I am working with a large project and I am trying to create a test that does the following thing: first, create 5 threads. Each one of this threads will create 4 threads, which in turn each one creates 3 other threads. All this happens until 0 threads.
I have _ThreadInit() function used to create a thread:
status = _ThreadInit(mainThreadName, ThreadPriorityDefault, &pThread, FALSE);
where the 3rd parameter is the output(the thread created).
What am I trying to do is start from a number of threads that have to be created n = 5, the following way:
for(int i = 0; i < n; i++){
// here call the _ThreadInit method which creates a thread
}
I get stuck here. Please, someone help me understand how it should be done. Thanks^^

Answer 1

Building on Eugene Sh.'s comment, you could create a function that takes a parameter, which is the number of threads to create, that calls itself recursively.
Example using standard C threads:
#include <stdbool.h>
#include <stdio.h>
#include <threads.h>
int MyCoolThread(void *arg) {
int num = *((int*)arg); // cast void* to int* and dereference
printf("got %d\n", num);
if(num > 0) { // should we start any threads at all?
thrd_t pool[num];
int next_num = num - 1; // how many threads the started threads should start
for(int t = 0; t < num; ++t) { // loop and create threads
// Below, MyCoolThread creates a thread that executes MyCoolThread:
if(thrd_create(&pool[t], MyCoolThread, &next_num) != thrd_success) {
// We failed to create a thread, set `num` to the number of
// threads we actually created and break out.
num = t;
break;
}
}
int result;
for(int t = 0; t < num; ++t) { // join all the started threads
thrd_join(pool[t], &result);
}
}
return 0;
}
int main() {
int num = 5;
MyCoolThread(&num); // fire it up
}
Statistics from running:
1 thread got 5
5 threads got 4
20 threads got 3
60 threads got 2
120 threads got 1
120 threads got 0