[Boost-bugs] [Boost C++ Libraries] #12275: bind fwds shared_ptr twice, invokes memfn with nullptr

Subject: [Boost-bugs] [Boost C++ Libraries] #12275: bind fwds shared_ptr twice, invokes memfn with nullptr
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-06-17 14:18:17

#12275: bind fwds shared_ptr twice, invokes memfn with nullptr
-----------------------------------------+---------------------
 Reporter:  Jason Mancini <jayrusman@…>  |      Owner:  pdimov
     Type:  Bugs                         |     Status:  new
Milestone:  To Be Determined             |  Component:  bind
  Version:  Boost 1.61.0                 |   Severity:  Problem
 Keywords:                               |
-----------------------------------------+---------------------
 Behavior started in 1.60, due to bind/bind.hpp changes around forwarding
 and rvalues. Short sample is shown below. This limitation needs to be
 mentioned in the boost docs, or somehow alter bind to work like before.
 Bind 1.59 would print the ptr address twice.  Bind 1.60 gets a nullptr on
 the second memfn call.  Quick fix for this sample is to change tFunc to
 use shared_ptr<...>const& such that it can't be forwarded.

 {{{
 #include <stdio.h>
 #include <boost/shared_ptr.hpp>
 #include <boost/make_shared.hpp>
 #include <boost/bind.hpp>
 #include <boost/function.hpp>

 using namespace boost;
 using tFunc = function<bool(shared_ptr<const Obj>)>;

 struct Obj { bool MF() const { printf("this %p\n", this); return true; }
 };

 int main() {
   shared_ptr<const Obj> sptr = make_shared<Obj>();
   tFunc BB;
   BB = bind(&Obj::MF, _1);
   BB = bind(BB, _1) && bind(&Obj::MF, _1);
   BB(sptr);
 }
 }}}

 Boost 1.59
 {{{
 this 0x117fc39
 this 0x117fc39
 }}}

 Boost 1.60
 {{{
 this 0x117fc39
 this (nil)
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12275>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.