here i post a working code, if anyone could compile it and try. In my previous mail i forgot to put the delete line in the Read function

#define _MULTI_THREADED
#include <iostream>
#include <pthread.h>
#include <unistd.h>
#include <stdio.h>

using namespace std;


class MyClass
{

char **myCharArray;

public:

void ModifyArray()

{
myCharArray = new char*[10];

for(int i = 0; i < 10; i++)
{
myCharArray[i] = new char[20];
sprintf(myCharArray[i], "%s%i", "mod ", i);

}




}

void ReadArray()
{
for(int i = 0; i < 10; i++)
{
cout << "element " << i << " "<<myCharArray[i]<<endl;
delete [] myCharArray[i];
}

}

};

MyClass *g_myclass;

void *ModClass(void *parm)
{
//mutex lock not shown
g_myclass->ModifyArray();

return NULL;
}

void *ReadClass(void *parm)
{
//mutex lock not shown
g_myclass->ReadArray();

return NULL;
}


int main()
{

int i = 0, rc;
pthread_t thread1, thread2;

g_myclass = new MyClass();

while(i < 1000)
{

//thread api not used, just pseudo-code
//1)
//createThread(ModClass);
rc = pthread_create(&thread1, NULL, ModClass, NULL);

//sleep(1)
usleep(500000);
//2)
rc = pthread_create(&thread2, NULL, ReadClass, NULL);

i++;

}

}

From: victorpy@xxxxxxxxxxx
To: c400-l@xxxxxxxxxxxx
Date: Tue, 5 Oct 2010 13:28:07 +0000
Subject: [C400-L] pthreads and c++ destructor


Hello to all,

I think im having a problem with threads and c++ destructor. I'll explain the problem

Supose i have a Class myclass that is global for all threads. A thread is created modify some attributes of the class then terminates. All the threads that modifies the class are detached.

After some time i try to access the modified attribute of the class, but this no longer have the value i put in the first thread. i.e. the value is gone or is trash.

Let me put a practical example

Class MyClass
{

char **myCharArray;

void ModifyArray()

{
myCharArray = new char*[10];

for(int i = 0; i < 10; i++)
myCharArray[i] = new char[20];
}

char ReadArray()
{
for(int i = 0; i < 10; i++)
cout << "element " << i << " "<<myCharArray[i]<<endl;

}

};

void *ModClass(void *parm)
{
//mutex lock not shown
g_myclass->ModifyArray();
}

void *ReadClass(void *parm)

{

//mutex lock not shown

g_myclass->ReadArray();

}

MyClass *g_myclass

int main()
{

int i = 0

g_myclass = new MyClass();

while(i < 10)
{

//thread api not used, just pseudo-code
//1)
createThread(ModClass);

sleep(10)
//2)
createThread(ReadClass);

i++;

}

}

1) In the first thread the array is modified using new operator, after that the thread is detached.
2) After some period of time the array is accessed for read, but in some cases after various iteration, the element in the array is gone.

Could it be that the modification of the array with new in the thread is deleted after the execution of the thread?. I think it could be that because i read about thread releasing resources after detaching

Any help will be welcome

Thanks

--
This is the C programming iSeries / AS400 (C400-L) mailing list
To post a message email: C400-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/c400-l
or email: C400-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/c400-l.


This thread ...

Follow-Ups:
Replies:

Follow On AppleNews
Return to Archive home page | Return to MIDRANGE.COM home page

This mailing list archive is Copyright 1997-2019 by midrange.com and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].