Re: A portable way of pointer alignment

"Alf P. Steinbach" <alfps@start.no> wrote in message
news:hm74pd$rk7$1@news.eternal-september.org...


[...]


I am getting some warnings, however the end result seems perfectly fine with
me:
_________________________________________________________________
#include <cstddef>
#include <iostream>

template< typename T >
inline std::size_t alignmentOf()
{
    struct X
    {
        char bah;
        T t;
    };

    return offsetof( X, t );
}

struct object_base
{
    char m_1[2];
    double m_d[6];
    long m_2[2];
    short m_3[14];

    virtual void foo() = 0;
};

struct object : public object_base
{
    char m_1x[2];

    void foo()
    {

    }
};

int
main()
{
    std::cout << "alignmentOf<object> == "
              << alignmentOf<object>()
              << std::endl;

    return 0;
}
_________________________________________________________________

Here are the warnings from gcc:
_________________________________________________________________
In function `size_t alignmentOf() [with T = object]':
instantiated from here
[Warning] invalid access to non-static data member `alignmentOf() [with T =
object]::X::t' of NULL object
[Warning] (perhaps the `offsetof' macro was used incorrectly)
_________________________________________________________________

Still, I am a bit weary of using `offsetof()' on a non-POD type. Perhaps I
am just way to paranoid!

;^D