CODEWITHSUNDEEP
c++multithreadingc++11
user1814023
user1814023

Reputation:

C++11 Threads: Exception when called using lambdas

I was reading about threads in C++11 and I did

#include <iostream>
#include <thread>

using namespace std;

void doSomething() { cout << "Inside doSomething " << endl; }
void doSomethingElse() { cout << "Inside doSomethingElse " << endl; }

int main(void)
{
    // Using LAMBDA expressions to call the functions.
    thread my_thread([](){ doSomething(); doSomethingElse(); });
    //my_thread.join(); ---------------> 1

    return 0;
}

I tried to execute the code without calling my_thread.join(), Visual Studio 2013 is throwing "abort() has been called". What is the reason?

Upvotes: 4

Views: 573

Answers (1)

Praetorian
Praetorian

Reputation: 109149

This has nothing to do with lambdas. If a thread is joinable when its destructor executes std::terminate will be called. To avoid this you must call thread::join or thread::detach. The standard even goes on to provide the rationale for this decision in a note.

From §30.3.1.3/1 [thread.thread.destr]

 ~thread();

If joinable(), calls std::terminate(). Otherwise, has no effects. [ Note: Either implicitly detaching or joining a joinable() thread in its destructor could result in difficult to debug correctness (for detach) or performance (for join) bugs encountered only when an exception is raised. Thus the programmer must ensure that the destructor is never executed while the thread is still joinable. —end note ]

In early C++0x drafts the wording used to be

If joinable() then detach(), otherwise no effects. ...

N2802 contains additional details of why implicit invocation of detach() in the destructor was later removed.

Upvotes: 6

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