Why does this throw an std::system_error ?

I was playing around with threads to improve some code.....with no luck whatsoever..
Any way.. I tried to get the following loop running concurrently.

Code:

            for(auto x=args.begin();x!=args.end();x++)
            {
                list l;
                if(is_list(*x,l)) *x = l.eval();
            }

My try:

Code:

            std::vector<std::thread> threads;
            list temp;
            for(auto x=args.begin();x!=args.end();x++)
                if(is_list(*x,temp))
                    threads.push_back(std::thread([](list l,std::string& ret){ret = l.eval();},temp,*x));
            for(auto t = threads.begin();t!=threads.end();t++)t->join();

(Notice that the list is passed by value...to avoid mishaps)
But clearly something(else?) has gone wrong...

N.B: list is NOT std::list

What is the exception and what object raised it?

Also the very fact that you need to remind people that list is not std::list is disturbing. Treat list like a reserved word.

Originally Posted by whiteflags

What is the exception and what object raised it?

Also the very fact that you need to remind people that list is not std::list is disturbing. Treat list like a reserved word.

I'm not sure... but it seems to stop when the 2nd thread is about to be created.

Originally Posted by gdb

(gdb)
Continuing.
terminate called after throwing an instance of 'std::system_error'
what(): Operation not permitted


Program received signal SIGABRT, Aborted.
0x00133416 in __kernel_vsyscall ()
(gdb)

The problem was a silly one.... I forgot to give the pthread flag to gcc.(..and another small bug in the loop itself)
Here is the final code:

Code:

			std::vector<std::thread> threads;
			for(auto x=args.begin();x!=args.end();x++)
			{
				threads.push_back
				(
					std::thread
					(
						[](list::iterator li)
						{
							list l;
							if(is_list(*li,l))
								*li = l.eval();
						},
						x
					)
				);
			}
			for(auto& t:threads)t.join();