[Bug other/63758] liblto_plugin.so has undefined reference to _environ on OSX

["iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63758

--- Comment #3 from Iain Sandoe <iains at gcc dot gnu.org> ---
I'm not disputing that the code is wrong…
 … and the change that you've put forward looks reasonable.

However, I'm not finding it easy to reproduce any failure - I've got a cross
from darwin12 => x86-64-linux-gnu with gold-enabled binutils.  

There's no failure at either build-time or runtime for the liblto plugin.

This is not entirely surprising (at least on the host I've tried), since the
plugin is linked with -Wl,-undefined,dynamic_lookup.  This means that _environ
will be resolved from the executable.

So I'm interested in how to reproduce the effect you show in c#1
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Subject: [Bug libstdc++/64096] std::list, set and map violate a rule about allocator::construct
Date: Fri, 28 Nov 2014 01:13:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd096

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to rylai from comment #0)
> As we can see, std::list implementation tries to call construct for whole
> list node (U = std::_List_node<int>),

This is already fixed on the SVN trunk, which will be GCC 5.

> and std::set and map (and also
> multiset and multimap) call it for right type (int or std::pair<const int,
> int>), but from rebinded allocator (T = std::_Rb_tree_node<int>).

I've discussed this extensively with the main author of  the C++11 allocator
proposals and other members of the committee. The standard is supposed to allow
that, the fact it doesn't is a defect, see
http://cplusplus.github.io/LWG/lwg-active.html#2218