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Re: [PATCH] Do without union of variable length arrays.

On Wed, 2015-10-07 at 02:24 +0300, Alexander Cherepanov wrote:
> On 2015-10-05 21:45, Mark Wielaard wrote:
> > On Fri, Oct 02, 2015 at 12:10:47AM +0300, Alexander Cherepanov wrote:
> >> Given that the current approach (before the patch) already required to write
> >> superfluous "->" perhaps an approach requiring a superfluous "*" will fit?
> >> Like this:
> >>
> >>    void *data = malloc (...);
> >>    T32 (*a32)[n] = data;
> >>    T64 (*a64)[n] = data;
> >>
> >> Then the use looks like "(*a32)[i].member". Clang seems to be happy and its
> >> UBSAN works fine.
> >
> > If that works that would probably be preferred since then ubsan can see
> > the array bounds and help catch issues.
> I believe it was not working in gcc 4.9. It works in newer gcc?

I am currently using gcc 5.1 where it definitely works.
-fsanitize=undefined finds array accesses outside variable arrays just
fine. It didn't work with gcc 4.8 though. I thought it also worked with
4.9, but haven't checked.

> > You can build and run elfutils
> > and the tests with configure --enable-sanitize-undefined to use ubsan
> > checking.
> Nice.

I am using it together with the afl fuzzer for finding issues.
And it found some nasty ones.



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