Hi Jonathan,
On 17 October 2016 at 13:56, Jonathan Wakely <jwak...@redhat.com> wrote:
> In C++17 the emplace_front and emplace_back members return a
> reference. There isn't a very neat way to implement this, so it's just
> lots of conditional compilation.
>
> This isn't an ABI break, because these member functions are templates
> and so the return type is part of the mangled name. We can't apply it
> retroactively to older standards though, because it breaks code that
> is valid in C++14, such as:
>
> void f(std::vector<int>& v) { return v.emplace_back(1); }
>
>
> * doc/xml/manual/status_cxx2017.xml: Update status.
> * doc/html/*: Regenerate.
> * include/bits/deque.tcc (deque::emplace_front,
> deque::emplace_back):
> Return a reference in C++17 mode.
> * include/bits/forward_list.h (forward_list::emplace_front):
> Likewise.
> * include/bits/stl_bvector.h (vector<bool>::emplace_back): Likewise.
> * include/bits/stl_deque.h (deque::emplace_front,
> deque::emplace_back):
> Likewise.
> * include/bits/stl_list.h (list::emplace_front, list::emplace_back):
> Likewise.
> * include/bits/stl_queue.h (queue::emplace): Likewise.
> * include/bits/stl_stack.h (stack::emplace): Likewise.
> * include/bits/stl_vector.h (vector::emplace_back): Likewise.
> * include/bits/vector.tcc (vector::emplace_back): Likewise.
> * include/debug/deque (__gnu_debug::deque::emplace_front)
> (__gnu_debug::deque::emplace_back): Likewise.
> * include/debug/vector (__gnu_debug::vector::emplace_back):
> Likewise.
> * testsuite/23_containers/deque/modifiers/emplace/cxx17_return.cc:
> New.
> * testsuite/23_containers/forward_list/modifiers/
> emplace_cxx17_return.cc: New.
> * testsuite/23_containers/list/modifiers/emplace/cxx17_return.cc:
> New.
> * testsuite/23_containers/queue/members/emplace_cxx17_return.cc:
> New.
> * testsuite/23_containers/stack/members/emplace_cxx17_return.cc:
> New.
> * testsuite/23_containers/vector/bool/emplace_cxx17_return.cc: New.
> * testsuite/23_containers/vector/modifiers/emplace/cxx17_return.cc:
> New.
>
> Tested powerpc64le-linux, committed to trunk.
>
The new tests (except for
23_containers/forward_list/modifiers/emplace_cxx17_return.cc) fail on
arm-none-eabi using default cpu/fpu/arch/mode:
/aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-arm-none-eabi/gcc3/arm-none-eabi/libstdc++-v3/src/.libs/libstdc++.a(future.o):
In function `__future_category_instance':
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/src/c++11/future.cc:64:
undefined reference to `__sync_synchronize'
/aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-arm-none-eabi/gcc3/arm-none-eabi/libstdc++-v3/src/.libs/libstdc++.a(locale.o):
In function `get_locale_cache_mutex':
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/src/c++98/locale.cc:36:
undefined reference to `__sync_synchronize'
/aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-arm-none-eabi/gcc3/arm-none-eabi/libstdc++-v3/src/.libs/libstdc++.a(locale_init.o):
In function `get_locale_mutex':
/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libstdc++-v3/src/c++98/locale_init.cc:66:
undefined reference to `__sync_synchronize'
Christophe
