[Bug c/30368] wrong result

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2007-01-05 20:13 -------
> anther, consider an example definite[2] of 'offsetof', if you think
> that is undefined, it's almost impossible to give a definite of
> offsetof.

> #define offsetof(TYPE,MEMBER)   ((size_t)&((TYPE*)0)->MEMBER)

The C standard still says that is undefined.  See 6.5.3.2/4.
Also GCC has a builtin for offsetof to get around the undefinedness of the
above.

You can also define offsetof like:
#define offsetof(TYPE,MEMBER)   (((size_t)&((TYPE*)128)->MEMBER) - 128)

Which gets around the undefined issue.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30368