Multiple Child Processes from one Parent Process - c

Question

I'm implementing a simple parent/child process program using fork. My goal is to create a user input number of child processes from a single parent and store their PIDs in a dynamic array. I manage to create the child processes (I think) using fork and store their PIDS. However, when I store the PIDs, I also store the 0 PID and what I believe another PID related to the processes yet this number is quite bigger than the child and parent.
How come this happens when clearly this is only done inside the parent process?
void createProcesses(int nProcess) {
int i;
int PID;
processIDS = calloc(nProcess, sizeof(long));
printf("*****Creating Processes*****\n");
printf("Parent Process: PID %d\n", getpid());
for (i = 0; i < nProcess; i++) {
PID = fork();
if (PID == 0) {
printf("Child Process: PID %d\n", getpid());
while(1){}
}
else if(PID != 0) {
// sleep(3);
// printf("Number of child processes created: %d\n", nProcess);
// updateProcessList();
*(processIDS + i) = PID;
printf("%d\n", PID);
}
}
for(i = 0; i < sizeof(processIDS); i++) {
printf("%ld\n", *(processIDS + i));
}
while(1) {
sleep(5);
updateProcessList();
}
}
processIDS is a long * global variable.

Answer 1

The problem is here:
for(i = 0; i < sizeof(processIDS); i++) {
printf("%ld\n", *(processIDS + i));
}
Because processIDS is a pointer, it's size is the size of a long *, probably 4 or 8, which is not what you want. If the value of nProcess is less than this, you'll be reading off the end of the dynamically allocated array, invoking undefined behavior.
You know there are nProcess processes created, so use that for your loop test:
for(i = 0; i < nProcess; i++) {
printf("%ld\n", *(processIDS + i));
}