Re: Code(using pthreads) working in gcc2.96,NOT working in gcc3.2

[Mihnea Balta <dark_lkml at mymail dot ro>]

There are two errors :)

First, you're declaring thread_ptr as a pointer which points to nowhere, so 
the pthread library writes the thread descriptor at a random memory address. 
Replace the declaration with:

pthread_t thread_ptr;

Then, when you create the thread, do:

if (0 != pthread_create (thread_ptr, &attr, start_proc, NULL)){

Secondly, the thread function must be something like:

void* start_proc(void*){
...
}

If you declare it something else, your program will end up by trashing the 
stack when that function returns, and you will get a segfault. You could also 
replace the pthread_exit(NULL) at the end with a simpler "return 0" or 
"return NULL".

On Monday 24 March 2003 16:25, Ulrich Prakash wrote:
> Hi all,
>
> The following code works fine in gcc2.96 but CRASHES in gcc3.2..
> The code is a simple program demonstrating the use of mutex....
>
> Please help me find out the reason for the CRASH,as also i could not use
> GDB with gcc3.2(but could use well with gcc2.96)...
> **************OUTPUT***********
> [uprakash at voicedsp trial]$ ./a.out
> Thread started
> Main Program
> New Thread id is 1026l
> Parent Thread id is 1024l
> End of Program
> Segmentation fault
> [uprakash at voicedsp trial]$
> *********END OF OUTPUT****************
>
> *********CODE**********************
> #include <pthread.h>
>
> static pthread_mutex_t  mutex_part = PTHREAD_MUTEX_INITIALIZER;
>
> void start_proc();
>
> int main()
> {
>          pthread_attr_t    attr;
>          pthread_attr_t    *temp_attr = NULL;
>          pthread_t *thread_ptr;
>
>          if (0 != pthread_attr_init (&attr)) {
>                  perror ("pthread_attr_init");
>                  goto thr_init;
>          }
>          if (0 != pthread_attr_setdetachstate (&attr,
> PTHREAD_CREATE_DETACHED)) {
>                  perror ("pthread_attr_setdetachstate");
>                  goto thr_init;
>          }
>          temp_attr = &attr;
>
>
> thr_init:
>           if (0 != pthread_create (thread_ptr, temp_attr, (void
> *)start_proc, NULL)) {
>                  perror ("pthread_create");
>          }
>
>      printf ("Main Program\n");
>
>      sleep (5);
>      pthread_mutex_lock (&mutex_part);
>      printf ("Parent Thread id is %ul\n",pthread_self() );
>      pthread_mutex_unlock (&mutex_part);
>
>      printf ("End of Program\n");
>
>      return 0;
>
> }
>
>
> void start_proc()
> {
>
>      printf ("Thread started\n");
>      pthread_mutex_lock (&mutex_part);
>      sleep (15);
>      printf ("New Thread id is %ul\n",pthread_self() );
>      pthread_mutex_unlock (&mutex_part);
>
>      pthread_exit (NULL);
>
>
> }
>
>
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