A default constructor is not synthesised if you created your own constructor with arguments. Since you gave Shape a constructor of your own, you’d have to explicitly write out a default Shape constructor now: class Shape { int k; public: Shape() : k(0) {} Shape(int n) : k(n) {} ~Shape() {} }; (You can leave … Read more
std::stringstream is the heavyweight champion. It takes into consideration things like the the stream’s imbued locale, and its functionality involves things like constructing a sentry object for the duration of the formatted operation, in order to deal with exception-related issues. Formatted input and output operations in the C++ libraries have some reputation for being heavyweight, … Read more
Quoting an excerpt from C++ Primer (5th Edition) section “18.2.2. Using Namespace Members” The scope of names introduced by a using directive is more complicated than the scope of names in using declarations. As we’ve seen, a using declaration puts the name in the same scope as that of the using declaration itself. It is … Read more
These two defect reports address your issue: Defect Report #316 Defect Report #317 Defect report 316 says (emphasis mine going forward): The rules for compatibility of function types in 6.7.5.3#15 do not define when a function type is “specified by a function definition that contains a (possibly empty) identifier list”, […] and it has a … Read more
Because when there is a template parameter involved, decltype returns an unqiue dependent type according to the standard, see below. If there is no template parameter then it resolves to an obvious size_t. So in this case you have to choose either both declaration and definition have an independent expression (e.g. size_t/decltype(sizeof(int))), as a return … Read more
Afaik, there are only two approaches that are compliant with strict aliasing rules: memcpy() and cast to char* with copying. All others read a float from memory that belongs to an uint32_t, and the compiler is allowed to perform the read before the write to that memory location. It might even optimize away the write … Read more
C11 says: (C11, 7.24.2.1p2) “The memcpy function copies n characters from the object pointed to by s2 into the object pointed to by s1.” &a + 1 itself is a valid pointer to integer addition but &a + 1 is not a pointer to an object, so the call invokes undefined behavior.
Does that mean that, in a modules world, for the compiler to be able to optimize away function calls we have to annotate them as inline even if they are defined in-class? To some degree. Inlining is an “as if” optimization, and inlining can happen even between translation units if the compiler is clever enough. … Read more
a is not constant expression(see standard quote below) and therefore: a || 1 Is not a constant expression either, although we know the expression has to evaluate to true the standard requires left to right evaluation here and I see no exceptions that would allow the compiler to skip the lvalue-to-rvalue conversion of a. but: … Read more
I think that both are wrong in C++171 and that the expected output should be: 4294967295 0 While the returned value is correct for the latest versions of both compilers, I think that the ios_base::failbit should be set, but I also think there is a confusion about the notion of field to be converted in … Read more