You’re missing the point why std::byte was invented in the first place. The reason it was invented is to hold a raw byte in memory without the assumption that it’s a character. You can see that in cppreference. Like char and unsigned char, it can be used to access raw memory occupied by other objects … Read more
You can use an initializer list for minmax: std::tie(a, b) = std::minmax({a, b}); This causes temporary objects to be created, just like when using unary plus, but has the benefit that it works with types lacking the unary plus operator too. using namespace std::string_view_literals; auto [a, b] = std::make_pair(“foo”sv, “bar”sv); std::tie(a, b) = std::minmax({a, b}); … Read more
Using auto __begin = begin_expr, __end = end_expr; requires both begin_expr and end_expr to return the same type. This means you cannot have a sentinel iterator type that is different from the beginning type. Using auto __begin = begin_expr ; auto __end = end_expr ; fixes that issue while proving full backwards compatibility with C++14.
The definition of aggregate changed since C++17. Before C++17 no base classes Since C++17 no virtual, private, or protected (since C++17) base classes That means, for B and D, they’re not aggregate type before C++17, then for B{} and D{}, value-initialization will be performed, then the defaulted default constructor will be called; which is fine, … Read more
This is talking about a well-established rule for templates – the same rule that allows compilers to diagnose template<class> void f() { return 1; }. [temp.res]/8 with the new change bolded: The program is ill-formed, no diagnostic required, if: no valid specialization can be generated for a template or a substatement of a constexpr if … Read more
No, there is no constexepr conditional operator. But you could wrap the whole thing in a lambda and immediately evaluate it (an IIFE): template<typename Mode> class BusAddress { public: explicit constexpr BusAddress(Address device) : mAddress([&]{ if constexpr (Mode::write) { return device.mDevice << 1; } else { return (device.mDevice << 1) | 0x01; } }()) { … Read more
What is the difference between seq and par/par_unseq? std::for_each(std::execution::seq, std::begin(v), std::end(v), function_call); std::execution::seq stands for sequential execution. It is the default if you do not specify the execution policy at all. It will force the implementation to execute all function calls in sequence. It is also guaranteed that everything is executed by the calling thread. … Read more
No, it is not possible. I distinctly remember reading somewhere that nested structured bindings are not allowed for C++17, but they are considering allowing it in a future standard. Can’t find the source though.
std::destroy_at provides two objective improvements over a direct destructor call: It reduces redundancy: T *ptr = new T; //Insert 1000 lines of code here. ptr->~T(); //What type was that again? Sure, we’d all prefer to just wrap it in a unique_ptr and be done with it, but if that can’t happen for some reason, putting … Read more
Due to Return Value Optimization (RVO), a destructor for std::string res in make_string_ok may not be called. The string object can be constructed on the caller’s side and the function may only initialize the value. The code will be equivalent to: void make_string_ok(std::string& res){ Writer w(res); } int main() { std::string res(“A”); make_string_ok(res); } That … Read more