I know I’m late, but this comes up when searching for “weak_ptr thread”, and Casey’s answer just isn’t the whole truth. Both shared_ptr and weak_ptr can be used from threads without further synchronization. For shared_ptr, there’s a lot of documentation (e.g. on cppreference.com or on stackoverflow). You can safely access shared_ptr‘s that point to the … Read more
The short answer is “templates are not string substitution”. void f(void) has meaning only so far as it is an alias for void f() in C++, in order to be backwards compatible with C. The first step is to use variadics, as noted elsewhere. The second step is figuring out how to map void returning … Read more
On the usefulness of const&&… (in general) The usefulness of the const&& qualifier on the member method is minimal at best. The object cannot be modified in the same manner as a && method would allow it to be modified; it is const after all (as noted, mutable does change this). So we will not … Read more
Concurrent writes to vector<bool> are never ok, because the underlying implementation relies on a proxy object of type vector<bool>::reference which acts as if it was a reference to bool, but in reality will fetch and update the bitfield bytes as needed. When using multiple threads without synchronization, the following might happen: Thread 1 is supposed … Read more
auto newvar1 = myvector; // vs: auto *newvar2 = myvector; Both of these are the same and will declare a pointer to std::vector<MyClass> (pointing to random location, since myvector is uninitialized in your example and likely contains garbage). So basically you can use any one of them. I would prefer auto var = getVector(), but … Read more
Both are correct. 20.8.9.1.2 forwards to 20.8.2 to describe the requirements and the effect of your call to bind. 20.8.2 is: 20.8.2 Requirements [func.require] 1 Define INVOKE(f, t1, t2, …, tN) as follows: — (t1.*f)(t2, …, tN) when f is a pointer to a member function of a class T and t1 is an object … Read more
Use the old for loop as: for (auto it = values.begin(); it != values.end(); ++it ) { auto & value = *it; //… } With this, you’ve value as well as iterator it. Use whatever you want to use. EDIT: Although I wouldn’t recommended this, but if you want to use range-based for loop (yeah, … Read more
I believe VS2010 to be right this time, and I’d check if I had the standard handy, but currently I don’t. Now, it’s exactly like the error message says: You can’t capture stuff outside of the enclosing scope of the lambda.† grid is not in the enclosing scope, but this is (every access to grid … Read more
When in doubt, pass by value. Now, you should only rarely be in doubt. Often values are expensive to pass and give little benefit. Sometimes you actually want a reference to a possibly mutating value stored elsewhere. Often, in generic code, you don’t know if copying is an expensive operation, so you err on the … Read more
Not so hard: #include <thread> void Test::runMultiThread() { std::thread t1(&Test::calculate, this, 0, 10); std::thread t2(&Test::calculate, this, 11, 20); t1.join(); t2.join(); } If the result of the computation is still needed, use a future instead: #include <future> void Test::runMultiThread() { auto f1 = std::async(&Test::calculate, this, 0, 10); auto f2 = std::async(&Test::calculate, this, 11, 20); auto res1 … Read more