static-members

Either I'm very tired or something weird is happening that I'm not aware of, because the code below is resulting in undefined symbols for Foo::A and Foo::B when linking . This is minimized as much as I could from a larger project, but shows the essence of what I'm looking at. #include <algorithm> struct Foo { static const int A = 1; static const int B = 2; }; int main() { return std::min(Foo::A, Foo::B); } Without the std::min function template it works fine , i.e. just return Foo::A. Also fine is when defining the static ints outside a class/struct (global in this simple case). However, as

I am trying to understand what this means, the code I am looking at has in .h typedef void (*MCB)(); static MCB m_process; in .C MCB Modes::m_process = NULL; And sometimes when I do m_process(); I get segmentations fault, it's probably because the memory was freed, how can I debug when it gets freed? I hope my questions are clear. It defines a pointer-to-function type. The functions return void, and the argument list is unspecified because the question is (currently, but possibly erroneously) tagged C; if it were tagged C++, then the function would take no arguments at all. To make it a

This is probably a bit of an unusual question, in that it asks for a fuller explanation of a short answer given to another question and of some aspects of the C++11 Standard related to it. For ease of reference, I shall sum up the referenced question here. The OP defines a class: struct Account { static constexpr int period = 30; void foo(const int &) { } void bar() { foo(period); } //no error? }; and is wondering why he gets no error about his usage of an in-class initialized static data member (a book mentioned this to be illegal). Johannes Schaub's answer states, that: This violates the One

I am new to C++. I have a class like this: class CodeTest { private: static const int TOTAL=100; }; Is TOTAL a declaration or a definition ? When I was reading Scott Meyer's book, it was mentioned that in the implementation file we need to define something like: const int CodeTest::TOTAL; Why is this required? The declaration in an implementation file outside of the header is required because otherwise every translation unit that includes this header would define its own object (that is, its own storage for the variable). This would violate the One Definition Rule . A consequence would be e.g.

class base { public: base a; }; It gives compilation error. class base { public: static base a; }; whereas this code does not give compilation error Because static class members are not stored in the class instance, that's why a static would work. Storing an object inside another object of the same type would break the runtime - infinite size, right? What would sizeof return? The size of the object needs to be known by the compiler, but since it contains an object of the same type, it doesn't make sense. I'm guessing the error is something like field ‘a’ has incomplete type This is because