libcxx on Linux: symbols used but not defined

[Alexey Samsonov]

On Thu, Feb 7, 2013 at 7:47 PM, Howard Hinnant <hhinnant at apple.com> wrote:

> On Feb 7, 2013, at 6:17 AM, Alexey Samsonov <samsonov at google.com> wrote:
>
> > Hi!
> >
> > I'm trying to build libcxx on Linux (Ubuntu Precise) using the following
> command:
> >
> > cmake -DLIBCXX_CXX_ABI=libsupc++
> '-DLIBCXX_LIBSUPCXX_INCLUDE_PATHS=/usr/include/c++/4.6;/usr/include/c++/4.6/x86_64-linux-gnu/.;'
> -DLIBCXX_ENABLE_EXCEPTIONS=OFF -DLIBCXX_ENABLE_SHARED=OFF
> -DLIBCXX_ENABLE_RTTI=OFF -DCMAKE_BUILD_TYPE=Release
> -DCMAKE_INSTALL_PREFIX=/tmp/tmp.boBpS5zFqt/libcxx_inst
> /tmp/tmp.boBpS5zFqt/libcxx
> >
> > and I want the result to be "hermetic" in the sense that resulting
> static library libc++.a doesn't reference undefined symbols from std::
> > However, I see the following problems:
> >
> > (libc++.a.new.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/new.cpp:function
> std::bad_alloc::~bad_alloc(): error: undefined reference to
> 'std::exception::~exception()'
> > (libc++.a.new.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/new.cpp:function
> std::bad_array_new_length::~bad_array_new_length(): error: undefined
> reference to 'std::exception::~exception()'
> > (libc++.a.new.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/new.cpp:function
> std::bad_array_new_length::~bad_array_new_length(): error: undefined
> reference to 'std::exception::~exception()'
> > (libc++.a.ios.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/ios.cpp:function
> std::__1::basic_ostream<char, std::__1::char_traits<char> >::flush():
> error: undefined reference to 'std::uncaught_exception()'
> > (libc++.a.ios.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/ios.cpp:function
> std::__1::basic_ostream<wchar_t, std::__1::char_traits<wchar_t> >::flush():
> error: undefined reference to 'std::uncaught_exception()'
> > (libc++.a.ios.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/ios.cpp:function
> std::__1::basic_ostream<char, std::__1::char_traits<char>
> >::sentry::~sentry(): error: undefined reference to
> 'std::uncaught_exception()'
> > (libc++.a.ios.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/ios.cpp:function
> std::__1::basic_ostream<char, std::__1::char_traits<char>
> >::sentry::~sentry(): error: undefined reference to
> 'std::uncaught_exception()'
> >
> (libc++.a.memory.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/memory.cpp:function
> std::__1::bad_weak_ptr::~bad_weak_ptr(): error: undefined reference to
> 'std::exception::~exception()'
> >
> (libc++.a.memory.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/memory.cpp:function
> vtable for std::__1::__shared_weak_count: error: undefined reference to
> 'std::__1::__shared_weak_count::__get_deleter(std::type_info const&) const'
> >
> (libc++.a.thread.cpp.o):/tmp/tmp.boBpS5zFqt/libcxx/src/thread.cpp:function
> std::__1::thread::~thread(): error: undefined reference to
> 'std::terminate()'
> >
> > What is the correct way to for that? I have the patch (attached) that
> works for me, but I'm not really sure it's correct
> > (especially the first part).
>
> Yeah, we tried this once:
>
> > --- include/memory    (revision 173248)
> > +++ include/memory    (working copy)
> > @@ -3629,10 +3629,9 @@
> >      long use_count() const _NOEXCEPT {return
> __shared_count::use_count();}
> >      __shared_weak_count* lock() _NOEXCEPT;
> >
> > -    // purposefully not protected with #ifndef _LIBCPP_NO_RTTI because
> doing so
> > -    //  breaks ABI for those clients who need to compile their projects
> with
> > -    //    -fno-rtti and yet link against a libc++.dylib compiled
> without -fno-rtti.
> > +#ifndef _LIBCPP_NO_RTTI
> >      virtual const void* __get_deleter(const type_info&) const _NOEXCEPT;
> > +#endif _LIBCPP_NO_RTTI
>
> and as the comments indicate, got bitten by it, at least on Apple
> platforms.
>
> Way forward:  Perhaps you could #ifdef it a little more in such a way that
> it isn't going to trigger except for someone trying to do exactly what you
> are doing:  Build a static lib on linux with rtti and exceptions off.  Or
> perhaps slightly more general:  Build a static lib with rtti and exceptions
> off.
>

Yes, I can add some #ifdefs here. But I also wonder about the second part
of the patch:
I have __GLIBCXX__ defined because of commit:

r173164 Saleem Abdulrasool: Ensure that __GLIBCXX__ is defined when
building with libsupc++.

and, as a result, I don't get definitions of terminate(),
uncaught_exception(), exception>::~exception() and exception::what() in the
resulting libc++ library,
yet these functions are referenced from it.

-- 
Alexey Samsonov, MSK
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