LLVM currently fails to build with GCC 6 (see openSUSE:Factory:Staging:Gcc6):

[ 5851s] FAILED: /home/abuild/rpmbuild/BUILD/llvm-3.7.0.src/stage1/bin/clang++  
 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS
-D__STDC_LIMIT_MA
CROS -fPIC -fvisibility-inlines-hidden -Wall -W -Wno-unused-parameter
-Wwrite-st
rings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long
-Wcovere
d-switch-default -Wnon-virtual-dtor -std=c++11 -ffunction-sections
-fdata-sectio
ns -O2 -g -DNDEBUG -fPIC -Ilib/CodeGen -I../lib/CodeGen -Iinclude -I../include  
  -fno-exceptions -MMD -MT
lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LexicalScopes.
cpp.o -MF lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/LexicalScopes.cpp.o.d -o
lib/Co
deGen/CMakeFiles/LLVMCodeGen.dir/LexicalScopes.cpp.o -c
../lib/CodeGen/LexicalSc
opes.cpp
[ 5851s] In file included from ../lib/CodeGen/LexicalScopes.cpp:17:
[ 5851s] In file included from ../include/llvm/CodeGen/LexicalScopes.h:20:
[ 5851s] In file included from ../include/llvm/ADT/ArrayRef.h:14:
[ 5851s] In file included from ../include/llvm/ADT/SmallVector.h:29:
[ 5851s] In file included from
/usr/lib64/gcc/x86_64-suse-linux/6/../../../../in
clude/c++/6/memory:79:
[ 5851s] In file included from
/usr/lib64/gcc/x86_64-suse-linux/6/../../../../in
clude/c++/6/functional:55:
[ 5851s]
/usr/lib64/gcc/x86_64-suse-linux/6/../../../../include/c++/6/tuple:1381
:14: error: no matching constructor for initialization of
'tuple<llvm::LexicalSc
ope *&&, const llvm::DILocalScope *&&, nullptr_t &&, bool &&>'
[ 5851s]     { return
tuple<_Elements&&...>(std::forward<_Elements>(__args)...);
 }
[ 5851s]              ^                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[ 5851s] ../lib/CodeGen/LexicalScopes.cpp:156:36: note: in instantiation of
func
tion template specialization 'std::forward_as_tuple<llvm::LexicalScope *&,
const
 llvm::DILocalScope *&, nullptr_t, bool>' requested here
[ 5851s]                               std::forward_as_tuple(Parent, Scope,
null
ptr,
[ 5851s]                                    ^
[ 5851s]
/usr/lib64/gcc/x86_64-suse-linux/6/../../../../include/c++/6/tuple:587:
18: note: candidate template ignored: disabled by 'enable_if' [with _Dummy =
voi
d]
[ 5851s]                  _TCC<_Dummy>::template
[ 5851s]                  ^


This looks like a clang bug to me (note how we use clang++ in the above.

Why again don't we use libc++ with clang? ...