The C++11 Standard (ISO/IEC 14882:2011) says in § C.1.1: char* p = “abc”; // valid in C, invalid in C++ For the C++ it’s OK as a pointer to a String Literal is harmful since any attempt to modify it leads to a crash. But why is it valid in C? The C++11 says also: … Read more
I know that at least one of the changes in C++11 that will cause some old code to stop compiling: the introduction of explicit operator bool() in the standard library, replacing old instances of operator void*(). Granted, the code that this will break is probably code that should not have been valid in the first … Read more
What is the correct way of using C++11’s range-based for? What syntax should be used? for (auto elem : container), or for (auto& elem : container) or for (const auto& elem : container)? Or some other? 4 Answers 4
What are the reasons for the existence of std::decay? In what situations is std::decay useful? 2 Answers 2
How do I remove from a map while iterating it? like: std::map<K, V> map; for(auto i : map) if(needs_removing(i)) // remove it from the map If I use map.erase it will invalidate the iterators 6 Answers 6
I have found an interesting performance regression in a small C++ snippet, when I enable C++11: #include <vector> struct Item { int a; int b; }; int main() { const std::size_t num_items = 10000000; std::vector<Item> container; container.reserve(num_items); for (std::size_t i = 0; i < num_items; ++i) { container.push_back(Item()); } return 0; } With g++ (GCC) … Read more
Ok, so the last time I wrote C++ for a living, std::auto_ptr was all the std lib had available, and boost::shared_ptr was all the rage. I never really looked into the other smart pointer types boost provided. I understand that C++11 now provides some of the types boost came up with, but not all of … Read more
I can see why the auto type in C++11 improves correctness and maintainability. I’ve read that it can also improve performance (Almost Always Auto by Herb Sutter), but I miss a good explanation. How can auto improve performance? Can anyone give an example? 4 Answers 4
I understand that std::atomic<> is an atomic object. But atomic to what extent? To my understanding an operation can be atomic. What exactly is meant by making an object atomic? For example if there are two threads concurrently executing the following code: a = a + 12; Then is the entire operation (say add_twelve_to(int)) atomic? … Read more
Using C++11, Ubuntu 14.04, GCC default toolchain. This code fails: constexpr std::string constString = “constString”; error: the type ‘const string {aka const std::basic_string}’ of constexpr variable ‘constString’ is not literal… because… ‘std::basic_string’ has a non-trivial destructor Is it possible to use std::string in aconstexpr? (apparently not…) If so, how? Is there an alternative way to … Read more
