unexpected result with char array and fork - c

Question

I'm trying to do a program with fork() in C but when I create a char array inside my code the program produces a unexpected result.(Instead of create 5 five sons it creates 6 sons? And the father?)
The code is this
#include <stdlib.h>
#include <stdio.h>
#define NUMPROC 5
int main (int argc, char *args[]){
//UNCOMMENTTHIS LINE
//char a[] = {'a','b','c','d','\0'};
int i;
pid_t status[NUMPROC];
for(i = 0; i< NUMPROC; i++){
status[i] = fork();
//fork error
if(status[i] == -1){
perror("fork() error");
exit(1);
}
//quit because I'm a son
if(status[i] == 0)
break;
}
//son
if(status[i] == 0){
printf("I'm son number: %i\n", i);
}
//father
else{
//wait sons
for(i = 0; i < NUMPROC; i++){
wait(&status[0]);
}
printf("Father terminated\n");
}
}
If you try to uncomment the array's line the result changes but this array is never used!
Can you explain me why??

Answer 1

//son
if(status[i] == 0){
printf("I'm son number: %i\n", i);
}
Code above doesn't work correctly in the father, for I will be equal to NUMPROC, which should be NUMPROC - 1.
This is a simple array index out of bounds problem. Value of status[NUMPROC] is uninitialized, it's value could be affected by the char array, so you will get different result.

Answer 2

Add the lines indicated and the problem will be obvious:
//son
if (i >= NUMPROC) // add this line
printf("ACK\n"); // and this line
if(status[i] == 0){
printf("I'm son number: %i\n", i);
}

Answer 3

there seems to be a misunderstanding about when/where each possible return state from the call to fork() occurs and how to handle the child state.
all the child actions need to be within the for() loop
all the parent actions (except the call to wait() need to be within the for() loop
The child actions must terminate in a call to exit()
Suggest the following code:
cleanly compiles
performs the desired operation
incorporates the initial comments on OPs question
and now, the proposed code
#include <stdlib.h> // exit(), EXIT_SUCCESS
#include <stdio.h> // printf()
#include <unistd.h> // fork(), pid_t
#include <sys/types.h> // #defines for waitpid()
#include <sys/wait.h> // waitpid()
#define NUMPROC (5)
int main ( void )
{
int i;
pid_t pid[NUMPROC] = {0};
for(i = 0; i< NUMPROC; i++)
{
pid[i] = fork();
switch( pid[i] )
{
case -1: // error
perror("fork() error");
// keep going,
// so if any current child's exit,
// they do not become zombie processes
break;
case 0: // child
printf("I'm son number: %i\n", i);
exit( EXIT_SUCCESS );
break;
default: // parent
break;
} // end switch
} // end for
// only father gets here
//wait sons
for(i = 0; i < NUMPROC; i++)
{
if( -1 != pid[i] )
{ // then child process successfully created
waitpid( pid[i], NULL, 0 );
}
}
printf("Father terminated\n");
}
here is the output from a typical run of the program:
I'm son number: 0
I'm son number: 1
I'm son number: 4
I'm son number: 2
I'm son number: 3
Father terminated