Shriramana Sharma wrote: > Apropos my recent questions regarding passing by reference etc the > following question comes to mind: > > When a class instance is created, does this also create a copy in memory > (from the class prototype) of the member functions or only of the data > members? > > Regarding static member functions I realize there is no meaning to have > an instance of the member function for each instance since the function > does not relate to an instance of the class. > > But even regarding non-static functions, I don't see any meaning in > having an instance of the function for each member of the class, since > all such functions would do basically the same thing, though with their > parent instance only. > > So what's the fact here? Is there any need for new copies of member > functions with each new instance of a class being created? *Are* such > new copies created by good compilers like GCC? Virtual methods are normally implemented via a table of function pointers which is shared by all instances of a given class. So a C++ virtual method call such as e.g. obj.foo(arg) results in code equivalent to the C expression (*obj.vtable->foo)(&obj, arg). Non-virtual methods are effectively just like C functions; the actual function is determined at compile time. -- Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
