Copyright (C) 2000-2012 |
GNU Info (gcc-295.info)Static DefinitionsDeclare *and* Define Static Members ----------------------------------- When a class has static data members, it is not enough to *declare* the static member; you must also *define* it. For example: class Foo { ... void method(); static int bar; }; This declaration only establishes that the class `Foo' has an `int' named `Foo::bar', and a member function named `Foo::method'. But you still need to define *both* `method' and `bar' elsewhere. According to the draft ANSI standard, you must supply an initializer in one (and only one) source file, such as: int Foo::bar = 0; Other C++ compilers may not correctly implement the standard behavior. As a result, when you switch to `g++' from one of these compilers, you may discover that a program that appeared to work correctly in fact does not conform to the standard: `g++' reports as undefined symbols any static data members that lack definitions. |