On April 6, 2017 4:51:01 PM GMT+02:00, Florian Weimer <fwei...@redhat.com> wrote: >On 04/06/2017 04:43 PM, Jonathan Wakely wrote: >> On 06/04/17 16:23 +0200, Richard Biener wrote: >>> On Thu, 6 Apr 2017, Florian Weimer wrote: >>> >>>> On 04/06/2017 04:11 PM, Bernd Edlinger wrote: >>>> >>>> > I think it is not too complicated to done in the C++ FE. >>>> > The FE looks for array of std::byte and unsigned char, >>>> > and sets the attribute when the final type is constructed. >>>> > >>>> > What I am trying to do is just extend the semantic of may_alias >>>> > a bit, and then have the C++ FE use it in the way it has to. >>>> >>>> We also need this for some POSIX and Linux kernel interfaces. A >>>> C++-only >>>> solution would not help with that. >>> >>> Example(s)? >> >> sockaddr_storage comes to mind. > >Right. The kernel also has many APIs which return multiple >variable-length data blocks, such as getdents64, and many more >interfaces in combination with read/recv system calls. Variable length > >means that you cannot declare the appropriate type after the first data > >item, so you technically have to use malloc. > >POSIX interfaces which exhibit a similar pattern are getpwnam_r and >friends, but for them, you can probably use malloc without ill effect >(although there are still performance concerns).
Can you give a concrete example which shows the issue and how typeless_storage helps? Thanks, Richard. >Thanks, >Florian
