On Thu, Oct 1, 2015 at 2:10 PM, Alexander Cherepanov <ch3r...@openwall.com> wrote:
> On 2015-09-16 18:25, Mark Wielaard wrote: > >> On Fri, 2015-09-11 at 12:22 -0700, Roland McGrath wrote: >> >>> It looks fine to me from a quick skim, but Mark should review and test >>> it too. >>> >> >> I am not super enthusiastic about this change, it seems to just take >> away type/size information that the compiler/bounds checking tools can >> use. >> > > I'm not sure I fully understand the problem. As I understand it unions of > VLAs are not Ok while VLAs are Ok and even desirable due to bounds > checking, right? > > Why not just use VLAs of unions? Cold memory? > I think this does not work because some part of elfutils walks through an array of T32 (or an array of T64), not an array of union of T32 and T64. > > 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. This looks fine to me. I don't mind either way. Anyone else prefers a32[i] or (*a32)[i]? -- chh > > > -- > Alexander Cherepanov >
