Create a dynamic number of threads - c

Question

I want to create a number of threads specified by the user. The code I have written for this is:
int nhijos = atoi(argv[1]);
thread = malloc(sizeof(pthread_t)*nhijos);
for (i = 0; i < nhijos; i++){
if (pthread_create ( &thread[i], NULL, &hilos_hijos, (void*) &info ) != 0){
perror("Error al crear el hilo. \n");
exit(EXIT_FAILURE);
}
Is this correct?

Answer 1

Yes, but I would do the following:
validate that argc > 1 before calling atoi(argv[1])
validate numberOfThreads is a positive number and less than a reasonable range. (In case the user types 1000000).
validate the return value from malloc is not null.
pthread_create will not set errno on failure. So perror may not be the right function to call on failure.
...
if (argc > 1)
{
int numberOfThreads = atoi(argv[1]);
if ((numberOfThreads <= 0) || (numberOfThreads > REASONABLE_THREAD_MAX))
{
printf("invalid argument for thread count\n");
exit(EXIT_FAILURE);
}
thread = malloc(sizeof(pthread_t)*numberOfThreads);
if (thread == NULL)
{
printf("out of memory\n");
exit(EXIT_FAILURE);
}
for (i = 0; i < numberOfThreads; i++)
{
if (pthread_create ( &thread[i], NULL, &hilos_hijos, (void*) &info ) != 0)
{
printf("Error al crear el hilo. \n");
exit(EXIT_FAILURE);
}
}

Answer 2

#include<stdio.h>
#include<pthread.h>
void* thread_function(void)
{
printf("hello");
}
int main(int argc,char *argv[])
{
int noOfThread= atoi(argv[1]);
pthread_t thread_id[noOfThread];
int i;
int status;
for(i=0;i<noOfThread;i++)
{
pthread_create (&thread_id[i], NULL , &thread_function, NULL);
}
for(i=0;i<noOfThread;i++)
pthread_join(thread_id[i],NULL);
}
Now compile thi and run as
./a.exe 3
So 3 thread will be created
In your code
1> why you are going to malloc ?
2> If malloc then why you are not going to free that ?