"Richard Guenther" <[EMAIL PROTECTED]> writes:
> On 9/9/07, Richard Guenther <[EMAIL PROTECTED]> wrote:
> >
> > Which brings back the fact that you cannot implement malloc in C
> > (you certainly remember the discussions about C++ placement new
> > handling wrt aliasing). To re-use the machinery we invented there
> > we would need to place a CHANGE_DYNAMIC_TYPE_EXPR for
> > the pointer assignment resulting from inlining a function with
> > attribute malloc set. As you say, unless we are inlining such functions
> > we are safe in practice.
>
> Actually this looks nice in general. We could implement placement
> new in C this way:
>
> extern inline T * __attribute__((malloc)) placement_new (void *p)
> { return p; }
>
> if we can somehow encode the target type here. Note that only
> type-based aliasing is a problem with this discussion - PTA will
> be obviously fine if new is inlined as it will see that both pointers
> are related and we loose the 'malloc' attribution on the target pointer
> during inlining.
CHANGE_DYNAMIC_TYPE_EXPR has the target type, of course. So perhaps
we need __attribute__ ((change_dynamic_type))?
Or actually of course __attribute__ ((malloc)) is fine but we could
throw in a CHANGE_DYNAMIC_TYPE_EXPR after any call to such a
function. That ought to do the right thing for C malloc
implementations as well, I think.
Ian
