Yes it is possible. First of all you need to decide if you want to accept only the type, or if you want to accept a implicitly convertible type. I use std::is_convertible in the examples because it better mimics the behavior of non-templated parameters, e.g. a long long parameter will accept an int argument. If … Read more
This has become much easier now. Search for cppstandard in your vs code extension settings and choose the version of C++ you want the extension to use from the drop down. In order to make sure your debugger is using the same version, make sure you have something like this for your tasks.json, where the … Read more
This is perfectly well-defined: void something(int *x) { reinterpret_cast<Point*>(x)->y = 42; } The Point object (p) and its x member are pointer-interconvertible, from [basic.compound]: Two objects a and b are pointer-interconvertible if: […] one is a standard-layout class object and the other is the first non-static data member of that object, or, if the object … Read more
Yes, in c++20. The problem was that determining uniqueness of a template non-type argument was difficult. c++20 adds in a <=> spaceship operator comparison. If it is non-user provided (and based only off non-user provided <=> in turn, repeat recursively) (and a few other requirements; see p0732), the type can be used as a non-type … Read more
The standard may fail to say properly that this is allowed, but it’s almost certainly supposed to be, and to the best of my knowledge, all implementations will treat this as defined behaviour. In order to facilitate the copying into an actual char[N] object, the bytes making up the f object can be accessed as … Read more
Quoting from C++ standard draft N4296, Section 5.16 Conditional operator, Paragraph 6.3: One or both of the second and third operands have pointer type; pointer conversions (4.10) and qualification conversions (4.4) are performed to bring them to their composite pointer type (Clause 5). The result is of the composite pointer type. Section 5 Expressions, Paragraph … Read more
You have to make the discarded statement dependent of the template parameters template <class…> constexpr std::false_type always_false{}; if constexpr(condition1){ … } else if constexpr (condition2) { …. } else if constexpr (condition3) { …. } else { static_assert(always_false<T>); } This is so because [temp.res]/8 – The program is ill-formed, no diagnostic required, if no valid … Read more
tl;dr: For C++17, __cplusplus is 201703L. What is the value of __cplusplus when using C++17? According to the draft standard N4594 §16.8/p1 Predefined macro names [cpp.predefined] (Emphasis Mine): The following macro names shall be defined by the implementation: __cplusplus The name __cplusplus is defined to the value 201402L when compiling a C++ translation unit.156 156) … Read more
The National Bodies from Spain and US have proposed to change back to the {} syntax because (P0488R0): The “structured bindings” proposal originally used braces “{}” to delimit binding identifiers. Those delimiters were changed to brackets “[]” under the assertion that they didn’t introduce any syntactic problem. However, they turned out to introduce syntactic ambiguity … Read more
The more things you check at compile time the fewer runtime bugs you have. variant guarantees that it contains one of a list of types (plus valueless by exception). It provides a way for you to guarantee that code operating on it considers every case in the variant with std::visit; even every case for a … Read more