rsmith added inline comments.
================ Comment at: libcxx/include/version:254 // # define __cpp_lib_concepts 201806L +# define __cpp_lib_constexpr_dynamic_alloc 201907L // # define __cpp_lib_constexpr_misc 201811L ---------------- ldionne wrote: > rsmith wrote: > > Should this be conditioned on compiler support being available? > So.. I've decided not to do that in this patch so far. > > The support for constexpr allocation was checked into Clang about a year ago, > right? I actually expect this to be a slightly contentious point, but I'd > like to assume that we're using a reasonably recent Clang. I don't see a > strong point for being able to use new libc++ headers with an old Clang > anyway, since vendors usually release the two together. IOW, supporting this > would add complexity for virtually no benefit. I do agree it's a slightly > more aggressive stance than we've had so far, but this sort of reasonable > assumption makes it so much easier to write stuff for libc++. OK, just a few thoughts then I'm going to bow out of this; this seems like a policy decision for the libc++ maintainers to make. In favor of dropping support for new libc++ + old clang: we generally don't permit version skew between different components of LLVM. It seems reasonable to expect all wanted parts of a particular LLVM release to be built together. Against dropping support for new libc++ + old clang: we do support installing more than one version of LLVM (and in particular more than one version of Clang) on the same system, but because libc++ defaults to being installed in `/usr/include/c++/v1`, we don't seem to encourage installing more than one version of libc++, so -- even assuming we only support the *newest* version of libc++ going into `/usr/include/c++/v1` -- new versions of libc++ need to work with old versions of Clang. I think (largely by accident) Clang will prefer a libc++ installed into `/usr/lib/clang/$VER/include` over one from `/usr/include/c++/v1`. If we switched to installing libc++ there, I don't see any technical barrier to version-locking them, though I'm not sure what story that leaves for use of libc++ with GCC and other compilers. It seems worth noting that this is exactly what libstdc++ does in order to need to support only one version of GCC. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D68364/new/ https://reviews.llvm.org/D68364 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
