Move to C++14

[jfb]

Summary

I just bumped the minimum compiler versions to support C++14 in D66188.

Following our process and our previous agreement, I'm now officially bumping the C++ version to 14 and updating the documentation.

[chandlerc]

This too LGTM, and again, thanks for driving this all the way through.

[hans]

Perhaps add a note in docs/ReleaseNotes.rst as well?

[jfb]

In D66195#1629120, @hans wrote:

Perhaps add a note in docs/ReleaseNotes.rst as well?

I can, but that seems odd: aren’t release notes for users of LLVM, not developers? In other words, what would someone reading this note take away from it, and do based on reading it?

[xbolva00]

llvm/cmake/modules/HandleLLVMOptions.cmake

24

Useless handling of C++1Y?

All compilers have to support C++14 now.

[hans]

In D66195#1629329, @jfb wrote:

In D66195#1629120, @hans wrote:

Perhaps add a note in docs/ReleaseNotes.rst as well?

I can, but that seems odd: aren’t release notes for users of LLVM, not developers? In other words, what would someone reading this note take away from it, and do based on reading it?

I think the releases are also used by folks doing various kinds of out-of-tree LLVM stuff, and this change might let them use C++14 in their code by default. But yeah, not a huge deal maybe.

[jfb]

llvm/cmake/modules/HandleLLVMOptions.cmake

24

r368890

[dexonsmith]

In D66195#1629514, @hans wrote:

In D66195#1629329, @jfb wrote:

In D66195#1629120, @hans wrote:

Perhaps add a note in docs/ReleaseNotes.rst as well?

I can, but that seems odd: aren’t release notes for users of LLVM, not developers? In other words, what would someone reading this note take away from it, and do based on reading it?

I think the releases are also used by folks doing various kinds of out-of-tree LLVM stuff, and this change might let them use C++14 in their code by default.

I agree with Hans that there should be an LLVM release note. Another action for an LLVM user (who, to be clear, is a developer of an LLVM-based compiler) would be to update their host toolchain before trying to migrate to the newer LLVM version.

[dexonsmith]

llvm/trunk/include/llvm/Support/type_traits.h

195–199 ↗

(On Diff #215166)

It seems like we don't need LLVM_IS_FINAL anymore, given that #if defined(__cplusplus) looks like it would always be true for this header. At least we can remove the #if guard.

[thakis]

It looks like building with gcc 5.1 (the new minimum) is broken after this change, while it worked fine previously:

/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/bin/g++  -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Itools/lld/ELF -I/b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF -I/b/s/w/ir/cache/builder/src/third_party/llvm/lld/include -Itools/lld/include -I/usr/include/libxml2 -Iinclude -I/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include -DLLVM_FORCE_HEAD_REVISION -fvisibility-inlines-hidden -Werror=date-time -std=c++14 -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wno-maybe-uninitialized -Wdelete-non-virtual-dtor -Wno-comment -fdiagnostics-color -ffunction-sections -fdata-sections -O3    -UNDEBUG  -fno-exceptions -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-rtti -MD -MT tools/lld/ELF/CMakeFiles/lldELF.dir/LinkerScript.cpp.o -MF tools/lld/ELF/CMakeFiles/lldELF.dir/LinkerScript.cpp.o.d -o tools/lld/ELF/CMakeFiles/lldELF.dir/LinkerScript.cpp.o -c /b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/LinkerScript.cpp
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/stl_algobase.h:71:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/memory:62,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/Optional.h:22,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:19,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringRef.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringMap.h:16,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/Support/Host.h:16,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/Hashing.h:48,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/include/lld/Common/LLVM.h:19,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/include/lld/Common/ErrorHandler.h:71,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/Config.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/LinkerScript.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/LinkerScript.cpp:13:
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h: In instantiation of ‘constexpr bool __gnu_cxx::__ops::_Iter_comp_iter<_Compare>::operator()(_Iterator1, _Iterator2) [with _Iterator1 = lld::elf::InputSectionBase*; _Iterator2 = lld::elf::InputSectionBase*; _Compare = std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)>]’:
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:1982:6:   required by substitution of ‘template<class _Res, class ... _ArgTypes> template<class _Functor> using _Invoke = decltype (std::__callable_functor(declval<_Functor&>())((declval<_ArgTypes>)()...)) [with _Functor = __gnu_cxx::__ops::_Iter_comp_iter<std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)> >; _Res = bool; _ArgTypes = {lld::elf::InputSectionBase*, lld::elf::InputSectionBase*}]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:1992:56:   required by substitution of ‘template<class _Res, class ... _ArgTypes> template<class _Functor> using _Callable = std::__and_<std::function<_Res(_ArgTypes ...)>::_NotSelf<_Functor>, std::__check_func_return_type<std::function<_Res(_ArgTypes ...)>::_Invoke<_Functor>, _Res> > [with _Functor = __gnu_cxx::__ops::_Iter_comp_iter<std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)> >; _Res = bool; _ArgTypes = {lld::elf::InputSectionBase*, lld::elf::InputSectionBase*}]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:2057:9:   required by substitution of ‘template<class _Functor, class> std::function<_Res(_ArgTypes ...)>::function(_Functor) [with _Functor = __gnu_cxx::__ops::_Iter_comp_iter<std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)> >; <template-parameter-1-2> = <missing>]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:130:46:   required from ‘constexpr __gnu_cxx::__ops::_Iter_comp_iter<_Compare> __gnu_cxx::__ops::__iter_comp_iter(_Compare) [with _Compare = std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/stl_algo.h:4933:43:   required from ‘void std::stable_sort(_RAIter, _RAIter, _Compare) [with _RAIter = lld::elf::InputSection**; _Compare = std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:1322:19:   required from ‘void llvm::stable_sort(R&&, Compare) [with R = llvm::MutableArrayRef<lld::elf::InputSection*>&; Compare = std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/LinkerScript.cpp:347:44:   required from here
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:123:46: error: no match for call to ‘(std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)>) (lld::elf::InputSectionBase&, lld::elf::InputSectionBase&)’
         { return bool(_M_comp(*__it1, *__it2)); }
                                              ^
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/memory:79:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/Optional.h:22,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:19,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringRef.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringMap.h:16,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/Support/Host.h:16,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/Hashing.h:48,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/include/lld/Common/LLVM.h:19,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/include/lld/Common/ErrorHandler.h:71,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/Config.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/LinkerScript.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/LinkerScript.cpp:13:
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:2266:5: note: candidate: _Res std::function<_Res(_ArgTypes ...)>::operator()(_ArgTypes ...) const [with _Res = bool; _ArgTypes = {lld::elf::InputSectionBase*, lld::elf::InputSectionBase*}]
     function<_Res(_ArgTypes...)>::
     ^
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:2266:5: note:   no known conversion for argument 1 from ‘lld::elf::InputSectionBase’ to ‘lld::elf::InputSectionBase*’

Has anyone seen this before? Any known workarounds?

[jfb]

In D66195#1630743, @dexonsmith wrote:

In D66195#1629514, @hans wrote:

In D66195#1629329, @jfb wrote:

In D66195#1629120, @hans wrote:

Perhaps add a note in docs/ReleaseNotes.rst as well?

I can, but that seems odd: aren’t release notes for users of LLVM, not developers? In other words, what would someone reading this note take away from it, and do based on reading it?

I think the releases are also used by folks doing various kinds of out-of-tree LLVM stuff, and this change might let them use C++14 in their code by default.

I agree with Hans that there should be an LLVM release note. Another action for an LLVM user (who, to be clear, is a developer of an LLVM-based compiler) would be to update their host toolchain before trying to migrate to the newer LLVM version.

Our process already handles this:

Once the RFC reaches consensus, update the CMake toolchain version checks as well as the getting started guide. We want to soft-error when developers compile LLVM. We say “soft-error” because the error can be turned into a warning using a CMake flag. This is an important step: LLVM still doesn’t have code which requires the new toolchains, but it soon will. If you compile LLVM but don’t read the mailing list, we should tell you!

So it's the soft-error that tells developers what to do, not release notes. I can certainly add something, but it doesn't seem to be the right audience. If we do want something in the release notes, I think we should amend the process document to say so, and it should be done when we change the toolchain requirements, not when we change the language version.

llvm/trunk/include/llvm/Support/type_traits.h

195–199 ↗

(On Diff #215166)

I did it separately yesterday, see llvm.org/r368910
I wanted to keep this change small... and it still had some explosions :)

[jfb]

Ugh that's an ugly one...

In D66195#1631620, @thakis wrote:

/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:1322:19:   required from ‘void llvm::stable_sort(R&&, Compare) [with R = llvm::MutableArrayRef<lld::elf::InputSection*>&; Compare = std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/LinkerScript.cpp:347:44:   required from here
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:123:46: error: no match for call to ‘(std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)>) (lld::elf::InputSectionBase&, lld::elf::InputSectionBase&)’

Looks like we do the following:

template <typename R, typename Compare>
void stable_sort(R &&Range, Compare C) {
  std::stable_sort(adl_begin(Range), adl_end(Range), C);
}

static void sortSections(MutableArrayRef<InputSection *> vec,
                         SortSectionPolicy k) {
  if (k != SortSectionPolicy::Default && k != SortSectionPolicy::None)
    llvm::stable_sort(vec, getComparator(k));
}

static std::function<bool(InputSectionBase *, InputSectionBase *)>
getComparator(SortSectionPolicy k) {
  switch (k) {
  case SortSectionPolicy::Alignment:
    return [](InputSectionBase *a, InputSectionBase *b) {
      // ">" is not a mistake. Sections with larger alignments are placed
      // before sections with smaller alignments in order to reduce the
      // amount of padding necessary. This is compatible with GNU.
      return a->alignment > b->alignment;
    };
  case SortSectionPolicy::Name:
    return [](InputSectionBase *a, InputSectionBase *b) {
      return a->name < b->name;
    };
  case SortSectionPolicy::Priority:
    return [](InputSectionBase *a, InputSectionBase *b) {
      return getPriority(a->name) < getPriority(b->name);
    };
  default:
    llvm_unreachable("unknown sort policy");
  }
}

Has anyone seen this before? Any known workarounds?

I haven't seen it before... taking a look now.

[jfb]

In D66195#1631746, @jfb wrote:

Ugh that's an ugly one...

In D66195#1631620, @thakis wrote:

/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:1322:19:   required from ‘void llvm::stable_sort(R&&, Compare) [with R = llvm::MutableArrayRef<lld::elf::InputSection*>&; Compare = std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/lld/ELF/LinkerScript.cpp:347:44:   required from here
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:123:46: error: no match for call to ‘(std::function<bool(lld::elf::InputSectionBase*, lld::elf::InputSectionBase*)>) (lld::elf::InputSectionBase&, lld::elf::InputSectionBase&)’

Looks like we do the following:

template <typename R, typename Compare>
void stable_sort(R &&Range, Compare C) {
  std::stable_sort(adl_begin(Range), adl_end(Range), C);
}

static void sortSections(MutableArrayRef<InputSection *> vec,
                         SortSectionPolicy k) {
  if (k != SortSectionPolicy::Default && k != SortSectionPolicy::None)
    llvm::stable_sort(vec, getComparator(k));
}

static std::function<bool(InputSectionBase *, InputSectionBase *)>
getComparator(SortSectionPolicy k) {
  switch (k) {
  case SortSectionPolicy::Alignment:
    return [](InputSectionBase *a, InputSectionBase *b) {
      // ">" is not a mistake. Sections with larger alignments are placed
      // before sections with smaller alignments in order to reduce the
      // amount of padding necessary. This is compatible with GNU.
      return a->alignment > b->alignment;
    };
  case SortSectionPolicy::Name:
    return [](InputSectionBase *a, InputSectionBase *b) {
      return a->name < b->name;
    };
  case SortSectionPolicy::Priority:
    return [](InputSectionBase *a, InputSectionBase *b) {
      return getPriority(a->name) < getPriority(b->name);
    };
  default:
    llvm_unreachable("unknown sort policy");
  }
}

Has anyone seen this before? Any known workarounds?

I haven't seen it before... taking a look now.

I have a repro, will try to figure out a workaround. It's fixed in 5.2. Talking to Jonathan Wakely we'd probably be better off on 5.5, but that'll be a separate discussion.

[jfb]

I have a repro, will try to figure out a workaround. It's fixed in 5.2. Talking to Jonathan Wakely we'd probably be better off on 5.5, but that'll be a separate discussion.

I have a fix. Building and testing... Will send a patch soon.

[jfb]

In D66195#1631797, @jfb wrote:

I have a repro, will try to figure out a workaround. It's fixed in 5.2. Talking to Jonathan Wakely we'd probably be better off on 5.5, but that'll be a separate discussion.

I have a fix. Building and testing... Will send a patch soon.

https://reviews.llvm.org/D66306

[thakis]

Thanks, that helped! Next one (build step 3810/3982, so hopefully not too much left after this):

FAILED: tools/llvm-nm/CMakeFiles/llvm-nm.dir/llvm-nm.cpp.o 
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/bin/g++  -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Itools/llvm-nm -I/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm -I/usr/include/libxml2 -Iinclude -I/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include -DLLVM_FORCE_HEAD_REVISION -fvisibility-inlines-hidden -Werror=date-time -std=c++14 -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wno-maybe-uninitialized -Wdelete-non-virtual-dtor -Wno-comment -fdiagnostics-color -ffunction-sections -fdata-sections -O3    -UNDEBUG  -fno-exceptions -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-rtti -MD -MT tools/llvm-nm/CMakeFiles/llvm-nm.dir/llvm-nm.cpp.o -MF tools/llvm-nm/CMakeFiles/llvm-nm.dir/llvm-nm.cpp.o.d -o tools/llvm-nm/CMakeFiles/llvm-nm.dir/llvm-nm.cpp.o -c /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/stl_algobase.h:71:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/memory:62,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/Optional.h:22,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:19,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringRef.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringSwitch.h:15,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:18:
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h: In instantiation of ‘constexpr bool __gnu_cxx::__ops::_Iter_comp_iter<_Compare>::operator()(_Iterator1, _Iterator2) [with _Iterator1 = {anonymous}::NMSymbol; _Iterator2 = {anonymous}::NMSymbol; _Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’:
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:1982:6:   required by substitution of ‘template<class _Res, class ... _ArgTypes> template<class _Functor> using _Invoke = decltype (std::__callable_functor(declval<_Functor&>())((declval<_ArgTypes>)()...)) [with _Functor = __gnu_cxx::__ops::_Iter_comp_iter<std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)> >; _Res = bool; _ArgTypes = {const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&}]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:1992:56:   required by substitution of ‘template<class _Res, class ... _ArgTypes> template<class _Functor> using _Callable = std::__and_<std::function<_Res(_ArgTypes ...)>::_NotSelf<_Functor>, std::__check_func_return_type<std::function<_Res(_ArgTypes ...)>::_Invoke<_Functor>, _Res> > [with _Functor = __gnu_cxx::__ops::_Iter_comp_iter<std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)> >; _Res = bool; _ArgTypes = {const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&}]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:2057:9:   required by substitution of ‘template<class _Functor, class> std::function<_Res(_ArgTypes ...)>::function(_Functor) [with _Functor = __gnu_cxx::__ops::_Iter_comp_iter<std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)> >; <template-parameter-1-2> = <missing>]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:130:46:   required from ‘constexpr __gnu_cxx::__ops::_Iter_comp_iter<_Compare> __gnu_cxx::__ops::__iter_comp_iter(_Compare) [with _Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/stl_algo.h:4729:70:   required from ‘void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<{anonymous}::NMSymbol*, std::vector<{anonymous}::NMSymbol> >; _Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:1125:12:   required from ‘void llvm::sort(IteratorTy, IteratorTy, Compare) [with IteratorTy = __gnu_cxx::__normal_iterator<{anonymous}::NMSymbol*, std::vector<{anonymous}::NMSymbol> >; Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:1130:13:   required from ‘void llvm::sort(Container&&, Compare) [with Container = std::vector<{anonymous}::NMSymbol>&; Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:724:31:   required from here
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:123:31: error: no match for ‘operator*’ (operand type is ‘{anonymous}::NMSymbol’)
         { return bool(_M_comp(*__it1, *__it2)); }
                               ^
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APFloat.h:19:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/Type.h:17,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/DerivedTypes.h:23,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/Function.h:29,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:21:
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2097:14: note: candidate: llvm::APInt llvm::operator*(llvm::APInt, uint64_t)
 inline APInt operator*(APInt a, uint64_t RHS) {
              ^
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2097:14: note:   candidate expects 2 arguments, 1 provided
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2102:14: note: candidate: llvm::APInt llvm::operator*(uint64_t, llvm::APInt)
 inline APInt operator*(uint64_t LHS, APInt b) {
              ^
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2102:14: note:   candidate expects 2 arguments, 1 provided
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/stl_algobase.h:71:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/memory:62,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/Optional.h:22,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:19,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringRef.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringSwitch.h:15,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:18:
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:123:39: error: no match for ‘operator*’ (operand type is ‘{anonymous}::NMSymbol’)
         { return bool(_M_comp(*__it1, *__it2)); }
                                       ^
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APFloat.h:19:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/Type.h:17,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/DerivedTypes.h:23,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/Function.h:29,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:21:
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2097:14: note: candidate: llvm::APInt llvm::operator*(llvm::APInt, uint64_t)
 inline APInt operator*(APInt a, uint64_t RHS) {
              ^
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2097:14: note:   candidate expects 2 arguments, 1 provided
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2102:14: note: candidate: llvm::APInt llvm::operator*(uint64_t, llvm::APInt)
 inline APInt operator*(uint64_t LHS, APInt b) {
              ^
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2102:14: note:   candidate expects 2 arguments, 1 provided

[jfb]

In D66195#1631941, @thakis wrote:

Thanks, that helped! Next one (build step 3810/3982, so hopefully not too much left after this):

FAILED: tools/llvm-nm/CMakeFiles/llvm-nm.dir/llvm-nm.cpp.o 
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/bin/g++  -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Itools/llvm-nm -I/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm -I/usr/include/libxml2 -Iinclude -I/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include -DLLVM_FORCE_HEAD_REVISION -fvisibility-inlines-hidden -Werror=date-time -std=c++14 -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wno-maybe-uninitialized -Wdelete-non-virtual-dtor -Wno-comment -fdiagnostics-color -ffunction-sections -fdata-sections -O3    -UNDEBUG  -fno-exceptions -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-rtti -MD -MT tools/llvm-nm/CMakeFiles/llvm-nm.dir/llvm-nm.cpp.o -MF tools/llvm-nm/CMakeFiles/llvm-nm.dir/llvm-nm.cpp.o.d -o tools/llvm-nm/CMakeFiles/llvm-nm.dir/llvm-nm.cpp.o -c /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/stl_algobase.h:71:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/memory:62,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/Optional.h:22,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:19,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringRef.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringSwitch.h:15,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:18:
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h: In instantiation of ‘constexpr bool __gnu_cxx::__ops::_Iter_comp_iter<_Compare>::operator()(_Iterator1, _Iterator2) [with _Iterator1 = {anonymous}::NMSymbol; _Iterator2 = {anonymous}::NMSymbol; _Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’:
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:1982:6:   required by substitution of ‘template<class _Res, class ... _ArgTypes> template<class _Functor> using _Invoke = decltype (std::__callable_functor(declval<_Functor&>())((declval<_ArgTypes>)()...)) [with _Functor = __gnu_cxx::__ops::_Iter_comp_iter<std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)> >; _Res = bool; _ArgTypes = {const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&}]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:1992:56:   required by substitution of ‘template<class _Res, class ... _ArgTypes> template<class _Functor> using _Callable = std::__and_<std::function<_Res(_ArgTypes ...)>::_NotSelf<_Functor>, std::__check_func_return_type<std::function<_Res(_ArgTypes ...)>::_Invoke<_Functor>, _Res> > [with _Functor = __gnu_cxx::__ops::_Iter_comp_iter<std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)> >; _Res = bool; _ArgTypes = {const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&}]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/functional:2057:9:   required by substitution of ‘template<class _Functor, class> std::function<_Res(_ArgTypes ...)>::function(_Functor) [with _Functor = __gnu_cxx::__ops::_Iter_comp_iter<std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)> >; <template-parameter-1-2> = <missing>]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:130:46:   required from ‘constexpr __gnu_cxx::__ops::_Iter_comp_iter<_Compare> __gnu_cxx::__ops::__iter_comp_iter(_Compare) [with _Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/stl_algo.h:4729:70:   required from ‘void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<{anonymous}::NMSymbol*, std::vector<{anonymous}::NMSymbol> >; _Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:1125:12:   required from ‘void llvm::sort(IteratorTy, IteratorTy, Compare) [with IteratorTy = __gnu_cxx::__normal_iterator<{anonymous}::NMSymbol*, std::vector<{anonymous}::NMSymbol> >; Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:1130:13:   required from ‘void llvm::sort(Container&&, Compare) [with Container = std::vector<{anonymous}::NMSymbol>&; Compare = std::function<bool(const {anonymous}::NMSymbol&, const {anonymous}::NMSymbol&)>]’
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:724:31:   required from here
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:123:31: error: no match for ‘operator*’ (operand type is ‘{anonymous}::NMSymbol’)
         { return bool(_M_comp(*__it1, *__it2)); }
                               ^
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APFloat.h:19:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/Type.h:17,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/DerivedTypes.h:23,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/Function.h:29,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:21:
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2097:14: note: candidate: llvm::APInt llvm::operator*(llvm::APInt, uint64_t)
 inline APInt operator*(APInt a, uint64_t RHS) {
              ^
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2097:14: note:   candidate expects 2 arguments, 1 provided
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2102:14: note: candidate: llvm::APInt llvm::operator*(uint64_t, llvm::APInt)
 inline APInt operator*(uint64_t LHS, APInt b) {
              ^
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2102:14: note:   candidate expects 2 arguments, 1 provided
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/stl_algobase.h:71:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/memory:62,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/Optional.h:22,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/STLExtras.h:19,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringRef.h:12,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/StringSwitch.h:15,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:18:
/b/s/w/ir/cache/builder/src/third_party/llvm-build-tools/gcc510trusty/include/c++/5.1.0/bits/predefined_ops.h:123:39: error: no match for ‘operator*’ (operand type is ‘{anonymous}::NMSymbol’)
         { return bool(_M_comp(*__it1, *__it2)); }
                                       ^
In file included from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APFloat.h:19:0,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/Type.h:17,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/DerivedTypes.h:23,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/IR/Function.h:29,
                 from /b/s/w/ir/cache/builder/src/third_party/llvm/llvm/tools/llvm-nm/llvm-nm.cpp:21:
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2097:14: note: candidate: llvm::APInt llvm::operator*(llvm::APInt, uint64_t)
 inline APInt operator*(APInt a, uint64_t RHS) {
              ^
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2097:14: note:   candidate expects 2 arguments, 1 provided
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2102:14: note: candidate: llvm::APInt llvm::operator*(uint64_t, llvm::APInt)
 inline APInt operator*(uint64_t LHS, APInt b) {
              ^
/b/s/w/ir/cache/builder/src/third_party/llvm/llvm/include/llvm/ADT/APInt.h:2102:14: note:   candidate expects 2 arguments, 1 provided

Thanks, here's a fix for this one: https://reviews.llvm.org/D66310

llvm/cmake/modules/HandleLLVMOptions.cmake

 include(CheckSymbolExists)
 
 if(CMAKE_LINKER MATCHES "lld-link" OR (WIN32 AND LLVM_USE_LINKER STREQUAL "lld") OR LLVM_ENABLE_LLD)
   set(LINKER_IS_LLD_LINK TRUE)
 else()
   set(LINKER_IS_LLD_LINK FALSE)
 endif()
 
-set(LLVM_CXX_STD_default "c++11")
+set(LLVM_CXX_STD_default "c++14")
 # Preserve behaviour of legacy cache variables
 if (LLVM_ENABLE_CXX1Y)
   set(LLVM_CXX_STD_default "c++1y")
 elseif (LLVM_ENABLE_CXX1Z)
   set(LLVM_CXX_STD_default "c++1z")
 endif()
 set(LLVM_CXX_STD ${LLVM_CXX_STD_default}
     CACHE STRING "C++ standard to use for compilation.")
 
 set(LLVM_ENABLE_LTO OFF CACHE STRING "Build LLVM with LTO. May be specified as Thin or Full to use a particular kind of LTO")
 string(TOUPPER "${LLVM_ENABLE_LTO}" uppercase_LLVM_ENABLE_LTO)

llvm/docs/CodingStandards.rst

 environment restrictions, historical restrictions, or due to third-party source
 code imported into the tree. Generally, our preference is for standards
 conforming, modern, and portable C++ code as the implementation language of
 choice.
 
 C++ Standard Versions
 ---------------------
 
-LLVM, Clang, and LLD are currently written using C++11 conforming code,
+LLVM, Clang, and LLD are currently written using C++14 conforming code,
 although we restrict ourselves to features which are available in the major
 toolchains supported as host compilers. The LLDB project is even more
 aggressive in the set of host compilers supported and thus uses still more
 features. Regardless of the supported features, code is expected to (when
-reasonable) be standard, portable, and modern C++11 code. We avoid unnecessary
+reasonable) be standard, portable, and modern C++14 code. We avoid unnecessary
 vendor-specific extensions, etc.
 
 C++ Standard Library
 --------------------
 
 Use the C++ standard library facilities whenever they are available for
 a particular task. LLVM and related projects emphasize and rely on the standard
 library facilities for as much as possible. Common support libraries providing
 functionality missing from the standard library for which there are standard
 interfaces or active work on adding standard interfaces will often be
 implemented in the LLVM namespace following the expected standard interface.
 
 There are some exceptions such as the standard I/O streams library which are
 avoided. Also, there is much more detailed information on these subjects in the
 :doc:`ProgrammersManual`.
 
-Supported C++11 Language and Library Features
+Supported C++14 Language and Library Features
 ---------------------------------------------
 
-While LLVM, Clang, and LLD use C++11, not all features are available in all of
+While LLVM, Clang, and LLD use C++14, not all features are available in all of
 the toolchains which we support. The set of features supported for use in LLVM
 is the intersection of those supported in the minimum requirements described
 in the :doc:`GettingStarted` page, section `Software`.
 The ultimate definition of this set is what build bots with those respective
 toolchains accept. Don't argue with the build bots. However, we have some
 guidance below to help you know what to expect.
 
 Each toolchain provides a good reference for what it accepts:
 
 * Clang: https://clang.llvm.org/cxx_status.html
-* GCC: https://gcc.gnu.org/projects/cxx-status.html#cxx11
+* GCC: https://gcc.gnu.org/projects/cxx-status.html#cxx14
 * MSVC: https://msdn.microsoft.com/en-us/library/hh567368.aspx
 
-In most cases, the MSVC list will be the dominating factor. Here is a summary
-of the features that are expected to work. Features not on this list are
-unlikely to be supported by our host compilers.
-
-* Rvalue references: N2118_
-
-  * But *not* Rvalue references for ``*this`` or member qualifiers (N2439_)
-
-* Static assert: N1720_
-* ``auto`` type deduction: N1984_, N1737_
-* Trailing return types: N2541_
-* Lambdas: N2927_
-
-  * But *not* lambdas with default arguments.
-
-* ``decltype``: N2343_
-* Nested closing right angle brackets: N1757_
-* Extern templates: N1987_
-* ``nullptr``: N2431_
-* Strongly-typed and forward declarable enums: N2347_, N2764_
-* Local and unnamed types as template arguments: N2657_
-* Range-based for-loop: N2930_
-
-  * But ``{}`` are required around inner ``do {} while()`` loops.  As a result,
-    ``{}`` are required around function-like macros inside range-based for
-    loops.
-
-* ``override`` and ``final``: N2928_, N3206_, N3272_
-* Atomic operations and the C++11 memory model: N2429_
-* Variadic templates: N2242_
-* Explicit conversion operators: N2437_
-* Defaulted and deleted functions: N2346_
-* Initializer lists: N2627_
-* Delegating constructors: N1986_
-* Default member initializers (non-static data member initializers): N2756_
-
-  * Feel free to use these wherever they make sense and where the `=`
-    syntax is allowed. Don't use braced initialization syntax.
-
-.. _N2118: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2118.html
-.. _N2439: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2439.htm
-.. _N1720: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2004/n1720.html
-.. _N1984: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1984.pdf
-.. _N1737: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2004/n1737.pdf
-.. _N2541: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2541.htm
-.. _N2927: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2927.pdf
-.. _N2343: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2343.pdf
-.. _N1757: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1757.html
-.. _N1987: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1987.htm
-.. _N2431: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2431.pdf
-.. _N2347: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2347.pdf
-.. _N2764: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2764.pdf
-.. _N2657: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm
-.. _N2930: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2930.html
-.. _N2928: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2928.htm
-.. _N3206: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3206.htm
-.. _N3272: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3272.htm
-.. _N2429: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2429.htm
-.. _N2242: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2242.pdf
-.. _N2437: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2437.pdf
-.. _N2346: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2346.htm
-.. _N2627: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2672.htm
-.. _N1986: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1986.pdf
-.. _N2756: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2756.htm
-
-The supported features in the C++11 standard libraries are less well tracked,
-but also much greater. Most of the standard libraries implement most of C++11's
-library. The most likely lowest common denominator is Linux support. For
-libc++, the support is just poorly tested and undocumented but expected to be
-largely complete. YMMV. For libstdc++, the support is documented in detail in
-`the libstdc++ manual`_. There are some very minor missing facilities that are
-unlikely to be common problems, and there are a few larger gaps that are worth
-being aware of:
-
-* Not all of the type traits are implemented
-* No regular expression library.
-* While most of the atomics library is well implemented, the fences are
-  missing. Fortunately, they are rarely needed.
-* The locale support is incomplete.
-
-Other than these areas you should assume the standard library is available and
-working as expected until some build bot tells you otherwise. If you're in an
-uncertain area of one of the above points, but you cannot test on a Linux
-system, your best approach is to minimize your use of these features, and watch
-the Linux build bots to find out if your usage triggered a bug. For example, if
-you hit a type trait which doesn't work we can then add support to LLVM's
-traits header to emulate it.
-
-.. _the libstdc++ manual:
-  https://gcc.gnu.org/onlinedocs/gcc-4.8.0/libstdc++/manual/manual/status.html#status.iso.2011
-
 Other Languages
 ---------------
 
 Any code written in the Go programming language is not subject to the
 formatting rules below. Instead, we adopt the formatting rules enforced by
 the `gofmt`_ tool.
 
 Go code should strive to be idiomatic. Two good sets of guidelines for what

 Some are advocating a policy of "almost always ``auto``" in C++11, however LLVM
 uses a more moderate stance. Use ``auto`` if and only if it makes the code more
 readable or easier to maintain. Don't "almost always" use ``auto``, but do use
 ``auto`` with initializers like ``cast<Foo>(...)`` or other places where the
 type is already obvious from the context. Another time when ``auto`` works well
 for these purposes is when the type would have been abstracted away anyways,
 often behind a container's typedef such as ``std::vector<T>::iterator``.
 
+Similarly, C++14 adds generic lambda expressions where parameter types can be
+``auto``. Use these where you would have used a template.
+
 Beware unnecessary copies with ``auto``
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 The convenience of ``auto`` makes it easy to forget that its default behavior
 is a copy.  Particularly in range-based ``for`` loops, careless copies are
 expensive.
 
 As a rule of thumb, use ``auto &`` unless you need to copy the result, and use

llvm/include/llvm/Support/Compiler.h

 #ifndef __has_cpp_attribute
 # define __has_cpp_attribute(x) 0
 #endif
 
 #ifndef __has_builtin
 # define __has_builtin(x) 0
 #endif
 
+#ifdef __cplusplus
+# if __cplusplus < 201402L
+#  error Expected C++14 or later.
+# endif
+#endif
+
 /// \macro LLVM_GNUC_PREREQ
 /// Extend the default __GNUC_PREREQ even if glibc's features.h isn't
 /// available.
 #ifndef LLVM_GNUC_PREREQ
 # if defined(__GNUC__) && defined(__GNUC_MINOR__) && defined(__GNUC_PATCHLEVEL__)
 #  define LLVM_GNUC_PREREQ(maj, min, patch) \
     ((__GNUC__ << 20) + (__GNUC_MINOR__ << 10) + __GNUC_PATCHLEVEL__ >= \
      ((maj) << 20) + ((min) << 10) + (patch))

llvm/include/llvm/Support/type_traits.h

 };
 
 
 } // end namespace llvm
 
 // If the compiler supports detecting whether a class is final, define
 // an LLVM_IS_FINAL macro. If it cannot be defined properly, this
 // macro will be left undefined.
-#if __cplusplus >= 201402L || defined(_MSC_VER)
+#if defined(__cplusplus) || defined(_MSC_VER)
 #define LLVM_IS_FINAL(Ty) std::is_final<Ty>()
 #elif __has_feature(is_final) || LLVM_GNUC_PREREQ(4, 7, 0)
 #define LLVM_IS_FINAL(Ty) __is_final(Ty)
 #endif
 
 #endif // LLVM_SUPPORT_TYPE_TRAITS_H