Re: [PING] Re: [PATCH] c++/67913, 67917 - fix new expression with wrong number of elements

[Martin Sebor <msebor at gmail dot com>]

On 11/26/2015 04:33 AM, Ramana Radhakrishnan wrote:
> > Cookies on ARM are 8-bytes [1], but sizeof ((size_t) n) is only 4-bytes,
> > so this check will fail (We'll ask for 500 bytes, the test here will only
> > be looking for 496).
> >
> > Would it undermine the test for other architectures if I were to swap out
> > the != for a >= ? I think that is in line with the "argument large enough
> > for the array" that this test is looking for, but would not catch bugs where
> > we were allocating more memory than neccessary.
> >
> > Otherwise I can spin a patch which skips the test for ARM targets.
>
> I didn't want to skip this for ARM, instead something that takes into account the cookie size - (very gratuitous hack was to just add 4 in a #ifdef __arm__ block). Something like attached, brown paper bag warning ;)

Thanks. I'll commit it today after some testing.

I should probably also check to see if there are other such targets
and try to find a way to generalize the test. (There should be a way
to expose the cookie size to programs, otherwise they have no way to
avoid buffer overflow in array forms of placement new).

Martin