[libcxx-dev] Commit implementing LWG 2510 (r372777) breaks compilation of LLVM

[Ilya Biryukov via libcxx-dev]

I'll have to revert the change to unbreak our integrate.
Sorry about the inconvenience.


On Wed, Sep 25, 2019 at 10:41 AM Ilya Biryukov <ibiryukov at google.com> wrote:

> Hi Louis,
>
> I'm seeing compilation failures while trying to compile clang with libc++
> after r372777.
> This is blocking our integrates.
>
> Checking for implicitly default-constructible types results in errors
> coming from access-checking.
> I would expect this shouldn't happen, given that the check is done in
> SFINAE context.
> Is there a quick workaround? Should we revert the change until it's found?
>
> Here is the compilation error itself:
>
> .../include/c++/v1/type_traits:2820:110: error: calling a protected
> constructor of class 'clang::ento::Loc'
> struct __is_implicitly_default_constructible<_Tp,
> decltype(__test_implicit_default_constructible<_Tp const&>({}))>
>
>                                    ^
> .../include/c++/v1/utility:350:18: note: in instantiation of template
> class 'std::__u::__is_implicitly_default_constructible<clang::ento::Loc,
> void>' requested here
>           return __is_implicitly_default_constructible<_U1>::value
>                  ^
> .../include/c++/v1/utility:341:19: note: in instantiation of function
> template specialization 'std::__u::pair<clang::ento::Loc,
> clang::ento::SVal>::_CheckArgs::__enable_implicit_default<clang::ento::Loc,
> clang::ento::SVal>' requested here
>               && !__enable_implicit_default<_U1, _U2>();
>                   ^
> .../include/c++/v1/utility:403:45: note: in instantiation of function
> template specialization 'std::__u::pair<clang::ento::Loc,
> clang::ento::SVal>::_CheckArgs::__enable_explicit_default<clang::ento::Loc,
> clang::ento::SVal>' requested here
>             _CheckArgsDep<_Dummy>::template __enable_explicit_default<_T1,
> _T2>()
>                                             ^
> .../include/c++/v1/utility:406:5: note: while substituting prior template
> arguments into non-type template parameter [with _Dummy = true]
>     pair() _NOEXCEPT_(is_nothrow_default_constructible<first_type>::value
> &&
>
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../include/c++/v1/utility:297:29: note: while substituting deduced
> template arguments into function template 'pair' [with _Dummy = (no value),
> $1 = (no value)]
> struct _LIBCPP_TEMPLATE_VIS pair
>                             ^
> third_party/llvm/llvm/include/llvm/Support/type_traits.h:90:7: note:
> (skipping 3 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see
> all)
> union trivial_helper {
>       ^
> third_party/llvm/llvm/include/llvm/Support/type_traits.h:176:40: note: in
> instantiation of static data member
> 'llvm::is_trivially_copyable<std::__u::pair<clang::ento::Loc,
> clang::ento::SVal> >::has_trivial_move_constructor' requested here
>       (has_deleted_move_constructor || has_trivial_move_constructor) &&
>                                        ^
> third_party/llvm/llvm/include/llvm/ADT/SmallVector.h:178:56: note: in
> instantiation of static data member
> 'llvm::is_trivially_copyable<std::__u::pair<clang::ento::Loc,
> clang::ento::SVal> >::value' requested here
> template <typename T, bool = is_trivially_copyable<T>::value>
>                                                        ^
> third_party/llvm/llvm/include/llvm/ADT/SmallVector.h:315:32: note: in
> instantiation of default argument for
> 'SmallVectorTemplateBase<std::__u::pair<clang::ento::Loc,
> clang::ento::SVal> >' required here
> class SmallVectorImpl : public SmallVectorTemplateBase<T> {
>                                ^~~~~~~~~~~~~~~~~~~~~~~~~~
> third_party/llvm/llvm/include/llvm/ADT/SmallVector.h:837:28: note: in
> instantiation of template class
> 'llvm::SmallVectorImpl<std::__u::pair<clang::ento::Loc, clang::ento::SVal>
> >' requested here
> class SmallVector : public SmallVectorImpl<T>, SmallVectorStorage<T, N> {
>                            ^
> third_party/llvm/llvm/tools/clang/lib/StaticAnalyzer/Core/Store.cpp:51:46:
> note: in instantiation of template class
> 'llvm::SmallVector<std::__u::pair<clang::ento::Loc, clang::ento::SVal>,
> 16>' requested here
>   SmallVector<CallEvent::FrameBindingTy, 16> InitialBindings;
>                                              ^
> third_party/llvm/llvm/tools/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SVals.h:322:3:
> note: declared protected here
>   Loc() = default;
>
> --
> Regards,
> Ilya Biryukov
>


-- 
Regards,
Ilya Biryukov
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