First, default argument promotions 6.5.2.2 If the expression that denotes the called function has a type that does not include a prototype, the integer promotions are performed on each argument, and arguments that have type float are promoted to double. These are called the default argument promotions. Now for integer promotions: 6.3.1.1 The following may … Read more
The short answer is: Yes, it is defined: scanf will attempt to convert a sequence of bytes from stdin as an integer written in base 10 with optional initial spaces and an optional sign. If successful, the number will be stored into x. scanf will then perform these steps a second time. The return value … Read more
I think you’re approaching this from a rather oblique angle, so to speak. According to §5.3.1/1: The unary * operator performs indirection: the expression to which it is applied shall be a pointer to an object type, or a pointer to a function type and the result is an lvalue referring to the object or … Read more
Firstly, the implicit object parameter is treated as a normal parameter as per 13.3.1.4: For non-static member functions, the type of the implicit object parameter is — “lvalue reference to cv X” for functions declared without a ref-qualifier or with the & ref-qualifier — “rvalue reference to cv X” for functions declared with the && … Read more
My reading of the standard is that std::memcpy is safe whenever the type is trivially copyable. From 9 Classes, we can see that unions are class types and so trivially copyable applies to them. A union is a class defined with the class-key union; it holds only one data member at a time (9.5). A … Read more
Is it guaranteed by the law? No. C++ says nothing about the representation of bool values. Is it guaranteed by practical reality? Yes. I mean, if you wish to find a C++ implementation that does not represent boolean false as a sequence of zeroes, I shall wish you luck. Given that false must implicitly convert … Read more
This boils down to whether or not a lambda’s type differs across translation units. If it does, it may affect template argument deduction and potentially cause different functions to be called – in what are meant to be consistent definitions. That would violate the ODR (see below). However, that isn’t intended. In fact, this problem … Read more
In the C Standard, only option (1) is initialization. In programming jargon, both may be considered initialization. Your question is really asking about the meanings of words. It’s normal for people to use words with various common meanings, instead of switching terminology for particular languages. Another example is “pass by reference”. Does C have pass … Read more
Yes. EDIT: C++11 Standard quote from §14.8.2 [temp.deduct] 8/ If a substitution results in an invalid type or expression, type deduction fails. An invalid type or expression is one that would be ill-formed if written using the substituted arguments. [ Note: Access checking is done as part of the substitution process. —end note ] This … 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