Boost C++ Libraries: Ticket #11875: Boost.Phoenix should not forward-declare std::unordered_set / map

cc set

Wed, 10 Feb 2016 21:28:52 GMT

cc braden@… added

There are other problems with this, as well, using gcc/libstdc++ (4.9, at least). For instance, this template specialization fails to compile if the problem Phoenix header gets included:

template <typename T, typename TypeT, typename KeyT, typename HashT, typename KeyEqualT, typename AllocatorT>
class foo<T, std::unordered_map<KeyT, TypeT, HashT, KeyEqualT, AllocatorT> >
{};

For the time being, I'm simply compiling my code with BOOST_PHOENIX_USING_LIBCPP defined, as this disables the forward declarations. But this is obviously undesirable if that macro ever gets used for something that is actually libc++-specific.

Jean-Michaël Celerier — Sat, 09 Apr 2016 12:35:31 GMT

Got another similar problem (in boost 1.60) in boost/phoenix/stl/algorithm/detail/is_unordered_set_or_map.hpp . The BOOST_PHOENIX_USING_LIBCPP trick seems to work however.

status, milestone changed; resolution set

Kohei Takahashi — Tue, 15 Nov 2016 14:38:28 GMT

status new → closed
resolution → fixed
milestone To Be Determined → Boost 1.62.0

This should be fixed in 1.62 release (https://github.com/boostorg/phoenix/pull/33).

status, version, milestone changed; resolution deleted

rogeeff@… — Fri, 19 May 2017 19:05:56 GMT

status closed → reopened
version Boost 1.60.0 → Boost 1.64.0
resolution fixed
milestone Boost 1.62.0 → Boost 1.65.0

This is still wrong. There is no legal way to forward declare std::unordered_set/std::unordered_map. According to the standard ([namespace.std]), these forward declarations have undefined behavior.

This need to change to

#include <unordered_map> #include <unordered_set>

status changed; resolution set

Kohei Takahashi — Wed, 31 May 2017 15:23:56 GMT

status reopened → closed
resolution → fixed

OK, fwd-decl will be replaced with include by https://github.com/boostorg/phoenix/pull/54.