On 19 April 2017 at 20:07, Jonathan Wakely <jwak...@redhat.com> wrote: > I know it's a bit late, but I'd like to propose deprecating the > libstdc++ extension that allows arithmetic on std::atomic<void*>. > Currently we make it behave like arithmetic on void*, which is also a > GNU extension (https://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html). > We also allow arithmetic on types such as std::atomic<void(*)()> which > is probably not useful (PR 69769). > > C++11 and C++14 were silent on the matter, but C++17 makes it > explicitly ill-formed (see https://wg21.link/p0558r1 page 2). I'm > implementing that for C++17 mode but would like it to be ill-formed > for all modes in a future release. > > So I'd like to apply this patch to the gcc-7/changes.html page: > > --- htdocs/gcc-7/changes.html 17 Apr 2017 22:12:35 -0000 1.77 > +++ htdocs/gcc-7/changes.html 19 Apr 2017 17:05:27 -0000 > @@ -38,6 +38,10 @@ > </li> > > <li>The Cilk+ extensions to the C and C++ languages have been > deprecated.</li> > + > + <li>The extension allowing arithmetic on > <code>std::atomic<void*></code> > + and types like <code>std::atomic<R(*)()></code> > + has been deprecated.</li> > </ul> > > <!-- .................................................................. --> > > > Does this seem reasonable, or do people think we need to keep this > feature, to match the core language extensions? >
I think it's reasonable. If users report massive concerns, we can certainly un-deprecate it. At the moment all that deprecation is doing for non-C++17 modes is giving users a fair warning of things to be aware of, and we can get feedback on that.
