Why does this throw an std::system_error ?

[manasij7479]

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.

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

My try:

            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

[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.

[manasij7479]

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.

(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)

[manasij7479]

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:

			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();