[llvm-bugs] [Bug 27115] New: libc++ problem with std::enable_shared_from_this

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https://llvm.org/bugs/show_bug.cgi?id=27115

            Bug ID: 27115
           Summary: libc++ problem with std::enable_shared_from_this
           Product: libc++
           Version: 3.8
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: cball at lgsinnovations.com
                CC: llvm-bugs at lists.llvm.org, mclow.lists at gmail.com
    Classification: Unclassified

Created attachment 16122
  --> https://llvm.org/bugs/attachment.cgi?id=16122&action=edit
Main program. Build with clang++ -std=c++11 -stdlib=libc++ main.cpp

We observe that the compiler fails when trying to build the simple example of
code provided with Apple clang++ version 703.0.29 on Mac 10.11 and with clang++
3.8.0 using libc++ on RedHat 7. g++ 4.9.2 on RedHat 7 does not exhibit the
problem. The error reported is:
clang++ -Werror -Wpedantic -Wall -std=c++11 main.cpp 
In file included from main.cpp:1:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/iostream:38:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/ios:216:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/__locale:15:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/string:439:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/algorithm:628:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:4092:61:
error: cannot cast 'const std::__1::enable_shared_from_this<Foo> *' to 'const
Foo *' via
      virtual base 'std::__1::enable_shared_from_this<Foo>'
                __e->__weak_this_.__ptr_ = const_cast<_Yp*>(static_cast<const
_Yp*>(__e));
                                                           
^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:4389:9:
note: in instantiation of function template specialization
      'std::__1::shared_ptr<Bar>::__enable_weak_this<Foo>' requested here
    __r.__enable_weak_this(__r.__ptr_);
        ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:4749:29:
note: in instantiation of function template specialization
      'std::__1::shared_ptr<Bar>::make_shared<int>' requested here
    return shared_ptr<_Tp>::make_shared(_VSTD::forward<_Args>(__args)...);
                            ^
main.cpp:12:35: note: in instantiation of function template specialization
'std::__1::make_shared<Bar, int>' requested here
    std::shared_ptr<Bar> a = std::make_shared<Bar>(2);
                                  ^
1 error generated.

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