On 31 December 2015 at 18:49, James Dennett <james.denn...@gmail.com> wrote: > On Thu, Dec 31, 2015 at 4:42 AM, Jonathan Wakely <jwakely....@gmail.com> > wrote: >> >> On 31 December 2015 at 11:54, Dominik Vogt wrote: >> > Is there a requirement for a certain minimum Glibc version for >> > this to work? >> >> It doesn't work with any glibc, because it doesn't declare the C++ >> overloads. >> >> Libstdc++ has an include/c_compatibility/math.h header that would >> include <cmath> (which declares the C++ overloads) and then pull them >> into the global namespace, but that isn't used on GNU/Linux, and would >> create other problems. >> > > What other problems? > > It's something of an assumption of the C++ Standard that it's practical for > C++ implementations to provide such wrappers to add overloads for C++. If > that's causing some fundamental problem then we should document it (and > ideally address it).
Not fundamental problems in the standard, just with the implementation of that header. It won't work as is and would need changes, but I don't think doing it that way is the right fix for GNU/Linux anyway. If we fix it in glibc we don't need that header. >> This is already in Bugzilla: >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60401 > > > I don't see much information on that bug, beyond an assertion that this > needs coordination with the underlying C library. There's a reference to an > e-mail thread, but there's little more information in the thread. Is that a question? :-) The point is just it's a known bug, not that Bugzilla contains all the background. > p.s. a tentatively ready DR indicates that the C++ headers should stop > splitting the overloads for std::abs/::abs up, so that if you include either > cmath or cstdlib (or the deprecated/C compatibility headers) you get the > full overload set. That seems the only way, short of a warning like > Clang's, to ensure that people write correct code when they use abs(). Yup.
