segmentation fault on joining pthread - c++

Question

I am trying to implement a thread interface class
I am having a problem with join() function, it gives me a segmentation fault
the output:
g++ threadInterface.cpp -lpthread
[murtraja#localhost src]$ ./a.out
Name: Thread # 0
Policy: FIFO
Scope: System
State: Detached
Name: my thread!
Policy: Round Robin
Scope: System
State: Joinable
Now running my thread!
Segmentation fault (core dumped)
What is interesting is that when I call gdb
and set a break at MyThread::run, the prime nos are printed
and I get a message that:
.......
48 is not prime
49 is not prime
0x000000000040141c in main ()
(gdb) s
Single stepping until exit from function main,
which has no line number information.
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7bc920a in pthread_join () from /lib64/libpthread.so.0
please refer the code and help me, i am new to threads. BTW, i've removed some code and kept only that is necessary
#include <iostream>
#include<pthread.h>
#include<stdio.h>
#include<cstring>
using namespace std;
class MyThread
{
int policy, state, scope;
char name[35];
char policyName[30];
char stateName[30];
char scopeName[30];
pthread_attr_t attrib;
pthread_t id;
static int count;
void setPrintables();
public:
MyThread(void);
MyThread(char*);
void setPolicy(int);
void setState(int);
void setScope(int);
void setName(char*);
void printDetails();
void loadDefaults();
void run(void *(*function)(void*));
void join();
};
int MyThread::count = 0;
MyThread::MyThread()
{
loadDefaults();
count++;
}
MyThread::MyThread(char* name)
{
loadDefaults();
strcpy(this->name, name);
count++;
}
void MyThread::loadDefaults()
{
pthread_attr_init(&attrib);
pthread_attr_setinheritsched(&attrib, PTHREAD_EXPLICIT_SCHED);
state = PTHREAD_CREATE_JOINABLE;
scope = PTHREAD_SCOPE_PROCESS;
policy = SCHED_OTHER;
sprintf(name, "Thread # %d", count);
}
void MyThread::join()
{
if(state == PTHREAD_CREATE_JOINABLE)
pthread_join(id, NULL);
}
void MyThread::run(void *(*function)(void*))
{
cout<<"Now running "<<name<<endl;
pthread_create(&id, &attrib, function, NULL);
//function(this);
}
void *printFactorials(void*)
{
for(int i=1; i<50; i++)
{
long fact = 1;
for(int j=i; j>=1; j--)
{
fact*=(long)j;
}
cout<<i<<"! = "<<fact<<endl;
}
}
void *printPrimes(void*)
{
for(int i=1; i<50; i++)
{
int c = 0;
for(int j=1; j<=i; j++)
{
if(!(i%j))
c++;
}
if(c==2)
cout<<i<<" is prime"<<endl;
else
cout<<i<<" is not prime"<<endl;
}
}
int main() {
char name[] = "my thread!";
MyThread t1, t2(name);
t1.setPolicy('F');
t1.setState('D');
t1.setScope('P');
t2.setPolicy('R');
t2.setState('J');
t2.setScope('P');
t1.printDetails();
cout<<endl;
t2.printDetails();
//t1.run(printFactorials);
//void* (*f)(void*) = printPrimes;
t2.run(printPrimes);
//t1.join();
t2.join();
return 0;
}
UPDATE:
Using pthread_create(&id, NULL, function, NULL);, gives no seg fault and everything works flawlessly.

Answer 1

The code looks good correct.
However you should be using the compiler option -pthread but just linking to the PThread library with the linker option -lpthread. (https://stackoverflow.com/a/1665110/694576)