The libstdc++ Debug Mode assertion is based on this rule in the standard, from [res.on.arguments] If a function argument binds to an rvalue reference parameter, the implementation may assume that this parameter is a unique reference to this argument. i.e. the implementation can assume that the object bound to the parameter of T::operator=(T&&) does not … Read more
The point of having a seed_seq is to increase the entropy of the generated sequence. If you have a random_device on your system, initializing with multiple numbers from that random device may arguably do that. On a system that has a pseudo-random number generator I don’t think there is an increase in randomness, i.e. generated … Read more
This is why you should not declare said member variables const. const member variables usually serve no purpose. If you don’t want users to mutate the FILE*, then don’t provide them with functions to do that, and if you want to stop yourself from mutating it by accident, then mark your functions const. However, do … Read more
The longstanding and unnecessary lack of a generic enum-to-string feature in C++ (and C) is a painful one. C++11 didn’t address this, and as far as I know neither will C++14. Personally I’d solve this problem using code generation. The C preprocessor is one way–you can see some other answers linked in the comments here … Read more
I believe Clang is correct to produce this error: The [temp.inst] section of the C++ standard in paragraph 10 says: If a function template or a member function template specialization is used in a way that involves overload resolution, a declaration of the specialization is implicitly instantiated (14.8.3). Forming the implicit conversion sequence necessary to … Read more
If you know that the key is in the map, you can utilize operator[] which returns a reference to the mapped value. Hence it will be map[key] = new_value. Be careful, however, as this will insert a (key, new_value) if the key does not already exist in the map. You can also use find which … Read more
C++ 11 I think the pertinent part are 3.9.1/1 In C++11 For character types, all bits of the object representation participate in the value representation. For unsigned character types, all possible bit patterns of the value representation represent numbers. These requirements do not hold for other types. Along with 3.9.1/7 The representations of integral types … Read more
The solution you propose: void add(T value) { _impl.push_back(value); } Would require some adjustment, since this way you do always end up performing one copy of value, even if you pass an rvalue to add() (two copies if you pass an lvalue): since value is an lvalue, the compiler won’t automatically move from it when … Read more
That code is most likely equal to this: TimePoint now_ = TimePoint::min(); That means, min() is a static method, and calling it using an instance is same as calling it like this, the instance is used just for determining the type. No black magic involved, that’s just two syntaxes for doing the same thing. As … Read more
Update for C++20: This can now easily be done in C++20: #include <chrono> #include <format> #include <iostream> #include <string> int main() { using namespace std::chrono_literals; std::chrono::time_point tp = std::chrono::sys_days{2016y/1/16} + 11h + 25min; std::string s = std::format(“{:%Y%m%d%H%M}”, tp); std::cout << s << ‘\n’; } Output: 201601161125 Demo. Original Answer: Howard Hinnant’s free, open source, header-only, … Read more