Re: [PATCH] test-stddef: test offsetof compliance

[Bruno Haible]

Paolo Bonzini wrote:
> >> #define offsetof(__a,__b) ((size_t)(&(((__a*)0)->__b)))
> In C, the macro will work in practice with all compilers.

In C++, however, some versions of g++ give a warning or error
if this macro is used for a type that is not a POD type (that is,
a type that has constructors or member functions or similar).
I ended up using this definition:

#if defined __GNUG__
  #define offsetof(type,ident)  ((size_t)&(((type*)1)->ident)-1)
#else
  #define offsetof(type,ident)  ((size_t)&(((type*)0)->ident))
#endif

Bruno