help about segmention fault

I always get a segmentation fault, can someone help me to modify. thanks in advance

Code:

---

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <string.h>
#define MAX 10
pthread_t thread[6];

void *thread1()
{

    int *a[16];
    int i, n;


    for (i = 0; i < 16; i++)
    {

    n=(size_t) ((rand() * 256.0) / (RAND_MAX + 1.0)) + 1;
        a[i] = (int*)malloc(n);
    if (a[i]==NULL)
        {
            printf("Error allocating memory!");
            exit (1);
        }

      printf("malloc a[%d]\n",i);

    }

    for (i = 16; i > 0; i--)
    {

        n=(size_t) ((rand() * 256.0) / (RAND_MAX + 1.0)) + 1;
        printf("remalloc a[%d]\n",i-1);
        a[i - 1] = (int*)realloc(a[i - 1], n);
    if ( a[i - 1]==NULL)
        {
            printf("Error reallocating memory!");
            exit (1);
        }


    }
    for (i = 0; i < 16; i += 2 )
        free(a[i]);
        printf("free1 a[%d]\n",i);
    for (i = 16; i > 0; i -= 2)
        free(a[i - 1]);
        printf("free2 a[%d]\n",i-1);
        pthread_exit(NULL);
}


void thread_create(void)
{
        int temp,i;
        memset(&thread, 0, sizeof(thread));          //comment1
        /**/
      for (i = 6; i > 0; i--)
{
        if((temp = pthread_create(&thread[i], NULL, thread1, NULL)) != 0)      //comment2
                printf("thread create failed\n");
        else
                printf("thread create\n");
}
}

void thread_wait(void)
{
  int i;
  for (i = 6; i > 0; i--)
{
        if(thread[i] !=0) {                  //comment4
                pthread_join(thread[i],NULL);
                printf("1\n");
        }
}
}

int main()
{

        printf("\n");
        thread_create();
        printf("\n");
        thread_wait();

        return 0;
}

---

You should have your debugger attached and when it breaks into the debugger, tell us which line is breaks on.

You're accessing thread out of bounds.

Why did you put this in C++?

Code:

---

pthread_t thread[6];

---

Valid indexes: 0 - 5

Code:

---

for (i = 6; i > 0; i--)
{
        if((temp = pthread_create(&thread[i], NULL, thread1, NULL)) != 0)

---

BOOM!

Gosh, I get an error on that "if" line , but I don't know why?

Code:

---

>  gcc -Wall -W -pedantic 20111104-pthread.cpp -l pthread -o 20111104-pthread.bin
20111104-pthread.cpp: In function ‘void thread_create()’:
20111104-pthread.cpp:66: error: invalid conversion from ‘void* (*)()’ to ‘void* (*)(void*)’
**********

void thread_create(void)
{
        int temp, i;
        memset(&thread, 0, sizeof(thread));          //comment1
        /**/
        for (i = 6; i > 0; i--)
{
        if((temp = pthread_create( &thread[i],
                                  NULL,
                                  thread1,
                                  NULL
                                )        // line 66
            )
            != 0)      //comment2
**********

// The prototype is:
  int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                    void *(*start_routine) (void *), void *arg);

---

Because thread function should be
void *thread1(void *p)

Not
void *thread1()

Oh yeah! (void*) IS an object! duh
Last night I was thinking (void), (void*) what's the difference? They're both nothing...:)
Oops so now there is an unused parameter, and how about this linker error?

Code:

---

>  gcc -Wall -W -pedantic 20111104-pthread.cpp -lpthread  -o 20111104-pthread.bin
20111104-pthread.cpp:9: warning: unused parameter ‘p’
/tmp/ccZQ2uCa.o:(.eh_frame+0x12): undefined reference to `__gxx_personality_v0'
collect2: ld returned 1 exit status

---

Who does that belong to?
thanks

Oh, I see the linker problem was because the gcc input filename extension was ,cpp. So I simply changed to .c.

So now I can run. Interestingly though, with the "for" condition left at:

Code:

---

pthread_t thread[6];
...
      for (i = 6; i > 0; i--){

---

I get no segfault. Should that be ok?

> I get no segfault. Should that be ok?
No, you just got the other side of the "luck" coin - in this case, your bad luck (and the OP's good luck).

Stepping outside an array is bad news, regardless of whether it crashes or not.

I still fail to see why you posted C code in the C++ section?