[Bug libstdc++/55123] New: [C++11] Construction of shared_ptr<const T> from unique_ptr<const T> fails

["yegor.derevenets at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55123

             Bug #: 55123
           Summary: [C++11] Construction of shared_ptr<const T> from
                    unique_ptr<const T> fails
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: yegor.derevenets@gmail.com


Hello,

construction of a shared_ptr from a unique_ptr to a const object seems not to
work, although it should. Preprocessed file is attached.

[yegor@tomato tmp]$ cat test.cpp
#include <memory>

void f() {
        std::unique_ptr<const int> y;
        std::shared_ptr<const int> x = std::move(y);
}


[yegor@tomato tmp]$ g++ -c -std=c++11 -save-temps test.cpp
In file included from
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/x86_64-unknown-linux-gnu/bits/c++allocator.h:34:0,
                 from
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/bits/allocator.h:48,
                 from
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/memory:65,
                 from test.cpp:1:
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/ext/new_allocator.h:
In instantiation of âstruct __gnu_cxx::new_allocator<const int>â:
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/bits/allocator.h:89:11:
  required from âclass std::allocator<const int>â
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/bits/shared_ptr_base.h:329:14:
  required from âstruct std::_Sp_counted_deleter<const int*,
std::default_delete<const int>, std::allocator<const int>,
(__gnu_cxx::_Lock_policy)2u>::_My_Deleterâ
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/bits/shared_ptr_base.h:374:24:
  required from âclass std::_Sp_counted_deleter<const int*,
std::default_delete<const int>, std::allocator<const int>,
(__gnu_cxx::_Lock_policy)2u>â
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/bits/shared_ptr_base.h:625:39:
  required from âstatic std::_Sp_counted_base<_Lp>*
std::__shared_count<_Lp>::_S_create_from_up(std::unique_ptr<_Up, _Ep>&&,
typename std::enable_if<(! std::is_reference<_Del>::value)>::type*) [with _Tp =
const int; _Del = std::default_delete<const int>; __gnu_cxx::_Lock_policy _Lp =
(__gnu_cxx::_Lock_policy)2u; typename std::enable_if<(!
std::is_reference<_Del>::value)>::type = void]â
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/bits/shared_ptr_base.h:549:43:
  required from âstd::__shared_count<_Lp>::__shared_count(std::unique_ptr<_Up,
_Ep>&&) [with _Tp = const int; _Del = std::default_delete<const int>;
__gnu_cxx::_Lock_policy _Lp = (__gnu_cxx::_Lock_policy)2u]â
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/bits/shared_ptr_base.h:855:4:
  required from âstd::__shared_ptr<_Tp, _Lp>::__shared_ptr(std::unique_ptr<_Up,
_Ep>&&) [with _Tp1 = const int; _Del = std::default_delete<const int>; _Tp =
const int; __gnu_cxx::_Lock_policy _Lp = (__gnu_cxx::_Lock_policy)2u]â
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/bits/shared_ptr.h:259:36:
  required from âstd::shared_ptr<_Tp>::shared_ptr(std::unique_ptr<_Up, _Ep>&&)
[with _Tp1 = const int; _Del = std::default_delete<const int>; _Tp = const
int]â
test.cpp:5:44:   required from here
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/ext/new_allocator.h:83:7:
error: âconst _Tp*
__gnu_cxx::new_allocator<_Tp>::address(__gnu_cxx::new_allocator<_Tp>::const_reference)
const [with _Tp = const int; __gnu_cxx::new_allocator<_Tp>::const_pointer =
const int*; __gnu_cxx::new_allocator<_Tp>::const_reference = const int&]â
cannot be overloaded
/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/../../../../include/c++/4.7.2/ext/new_allocator.h:79:7:
error: with â_Tp*
__gnu_cxx::new_allocator<_Tp>::address(__gnu_cxx::new_allocator<_Tp>::reference)
const [with _Tp = const int; __gnu_cxx::new_allocator<_Tp>::pointer = const
int*; __gnu_cxx::new_allocator<_Tp>::reference = const int&]â


[yegor@tomato tmp]$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-unknown-linux-gnu/4.7.2/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /build/src/gcc-4.7.2/configure --prefix=/usr --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-clocale=gnu --disable-libstdcxx-pch
--enable-libstdcxx-time --enable-gnu-unique-object --enable-linker-build-id
--with-ppl --enable-cloog-backend=isl --disable-ppl-version-check
--disable-cloog-version-check --enable-lto --enable-gold --enable-ld=default
--enable-plugin --with-plugin-ld=ld.gold --with-linker-hash-style=gnu
--enable-multilib --disable-libssp --disable-build-with-cxx
--disable-build-poststage1-with-cxx --enable-checking=release
Thread model: posix
gcc version 4.7.2 (GCC)