On Wed, Mar 9, 2011 at 07:52, Chad Nelson <chad.thecomfychair@gmail.com> wrote:
On Wed, 9 Mar 2011 09:41:58 -0500 "Stewart, Robert" <Robert.Stewart@sig.com> wrote:
magnitude_t: * It probably needs to be POD for you to make assumptions about the layout.
The "struct hack" is a standard C idiom [...]
A C struct is POD.
So far as I've been able to determine, a C++ struct with some non-virtual functions, and that doesn't inherit from anything, acts like POD in every case. There's no need for a vtable or any other appended data that I've been able to imagine, and there certainly isn't on the two compilers I've directly tested (MSVC on Windows and GCC on Ubuntu Linux).
C++0x offers the definition of a "standard-layout class" in 9 [class]/7, with layout specified by 9.2 [class.mem]. Precise requirements: — has no non-static data members of type non-standard-layout class (or array of such types) or reference, — has no virtual functions (10.3) and no virtual base classes (10.1), — has the same access control (Clause 11) for all non-static data members, — has no non-standard-layout base classes, — either has no non-static data members in the most derived class and at most one base class with non-static data members, or has no base classes with non-static data members, and — has no base classes of the same type as the first non-static data member.