Boost C++ Libraries: Ticket #6131: #define foreach BOOST_FOREACH causes weird compile error in certain circumstances with boost 1.48

attachment set

loonycyborg — Thu, 17 Nov 2011 14:17:22 GMT

attachment → foreachtest.cpp

Test case.

Fri, 18 Nov 2011 01:32:27 GMT

before certain other boost headers.

Specifically, those Boost headers are

boost/multi_index/hashed_index.hpp
boost/multi_index/ordered_index.hpp
boost/multi_index/random_access_index.hpp
boost/multi_index/sequenced_index.hpp

and headers that eventually include them, right?

Here are related threads in Boost-users ML:

Eric Niebler — Fri, 18 Nov 2011 04:38:27 GMT

Attempted a workaround on trunk here: <https://svn.boost.org/trac/boost/changeset/75540>. I'll merge to release if the tests don't explode. I don't see why they would.

status changed; resolution set

Eric Niebler — Wed, 23 Nov 2011 04:59:35 GMT

status new → closed
resolution → fixed

(In [75634]) merge [75540] from trunk, fixes #6131

status, version changed; resolution deleted

anonymous — Mon, 05 Mar 2012 13:33:30 GMT

status closed → reopened
version Boost 1.48.0 → Boost 1.49.0
resolution fixed

I use just this #define in my code and I have actually _started_ to get compiler error with boost 1.49 (Xcode 4.3, LLVM compiler 3.1):

Redefinition of 'is_lightweight_proxy' Redefinition of 'is_noncopyable'

And even more errors that say:

No matching function for call to 'should_copy_impl'

anonymous — Mon, 05 Mar 2012 13:37:01 GMT

Replying to anonymous:

I use just this #define in my code and I have actually _started_ to get compiler error with boost 1.49 (Xcode 4.3, LLVM compiler 3.1):

Redefinition of 'is_lightweight_proxy' Redefinition of 'is_noncopyable'

And even more errors that say:

No matching function for call to 'should_copy_impl'

FWIW the error actually comes up when using BOOST_REVERSE_FOREACH (which I use alongside foreach):

../Game/Widgets.hpp:130:9: error: no matching function for call to 'should_copy_impl'

PASS_TOUCH(touchBegan) ^~

../Game/Widgets.hpp:124:17: note: expanded from macro 'PASS_TOUCH'

BOOST_REVERSE_FOREACH (const WidgetPtr& child, children) \

/usr/local/include/boost/foreach.hpp:1117:77: note: expanded from macro 'BOOST_REVERSE_FOREACH'

if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_end) = BOOST_FOREACH_REND(COL)) {} else \

/usr/local/include/boost/foreach.hpp:1051:9: note: expanded from macro 'BOOST_FOREACH_REND'

, BOOST_FOREACH_SHOULD_COPY(COL))

/usr/local/include/boost/foreach.hpp:961:6: note: expanded from macro 'BOOST_FOREACH_SHOULD_COPY'

(boost::foreach_detail_::should_copy_impl( \

^~

So maybe this is actually another bug?

Eric Niebler — Mon, 05 Mar 2012 17:18:09 GMT

It's impossible to say without looking at a repro. Can you attach code that demonstrates the problem?

Eric Niebler — Mon, 19 Mar 2012 22:05:16 GMT

In light of #6455, it seems this "fix" is doing more harm than good. I've reverted foreach to the 1.47 version on trunk and plan to close this bug "won't fix". Sorry, I tried.

status changed; resolution set

Eric Niebler — Tue, 27 Mar 2012 19:28:34 GMT

status reopened → closed
resolution → fixed

(In [77591]) merge [77416] from trunk, fixes #6131, fixes #6455

anonymous — Tue, 05 Jun 2012 22:07:13 GMT

In 1.49 under Visual Studio 2008, I am now getting this error whenever I DON'T include <boost/foreach.hpp> until AFTER I #define foreach BOOST_FOREACH:

'boost::BOOST_FOREACH::is lightweight proxy' : class template has already been defined

foreach_fwd.hpp(62) : see declaration of 'boost::BOOST_FOREACH::is_lightweight_proxy'

Simple test that fails:

#define foreach BOOST_FOREACH #include <boost/foreach.hpp>

It works fine in the other order, i.e., the include before the #define. This never used to be a problem.

Eric Niebler — Tue, 05 Jun 2012 22:16:29 GMT

Foreach was broken in 1.49. As you can see from the comment above, the change was reverted and the fix has already been migrated to the release branch. In 1.50 (currently in beta), the problem should be fixed.

anonymous — Tue, 03 Jul 2012 19:45:02 GMT

The problem still occur in 1.50.0. I stumbled on it while building mkvtoolnix 5.0.1 using clang 3.1 from Xcode 4.3.3. The patches from changeset 75540 are still a valid cure.

Eric Niebler — Tue, 03 Jul 2012 20:58:08 GMT

As you can see from the comments above yours, the patch in [75540], which was released as part of Boost 1.49, caused more problems than it solved. The bug is unfortunate, but there is nothing that can be done at this point, AFAIK. Sorry.

version changed; cc set

monster.romster@… — Sat, 07 Jul 2012 01:44:45 GMT

cc monster.romster@… added
version Boost 1.49.0 → Boost 1.50.0

I tried that patch https://svn.boost.org/trac/boost/changeset/75540 but then boost fails to compile:

    "ccache" "g++"  -ftemplate-depth-128 -O2 -march=i686 -pipe -O3 -Wno-deprecated -fno-strict-aliasing -finline-functions -Wno-inline -Wall -fPIC  -DBOOST_ALL_NO_LIB=1 -DBOOST_GRAPH_DYN_LINK=1 -DBOOST_HAS_ICU=1 -DNDEBUG  -I"." -I"/usr/include" -I"libs/graph/src" -c -o "bin.v2/libs/graph/build/gcc-4.5.3/release/graphml.o" "libs/graph/src/graphml.cpp"
In file included from libs/graph/src/graphml.cpp:14:0:
./boost/foreach.hpp:126:16: error: 'boost::boost::mpl' has not been declared
./boost/foreach.hpp:126:21: error: expected '{' before 'false_'
./boost/foreach.hpp:127:5: error: invalid type in declaration before '{' token
./boost/foreach.hpp:127:5: error: template declaration of 'int boost::boost::foreach::false_'
./boost/foreach.hpp:127:5: warning: extended initializer lists only available with -std=c++0x or -std=gnu++0x
./boost/foreach.hpp:137:16: error: 'boost::boost::mpl' has not been declared
./boost/foreach.hpp:137:21: error: expected '{' before 'or_'
./boost/foreach.hpp:137:24: error: expected initializer before '<' token
In file included from libs/graph/src/graphml.cpp:14:0:
./boost/foreach.hpp:168:8: error: 'BOOST_FOREACH' in namespace 'boost::boost' does not name a type

So I am forced to keep boost at 1.49.0 due to wesnoth failing on 1.50.0

[ 15%] Building CXX object src/CMakeFiles/wesnoth-game.dir/font.cpp.o
In file included from /usr/ports/work/wesnoth/src/wesnoth-1.10.3/src/shared_object.hpp:21:0,
                 from /usr/ports/work/wesnoth/src/wesnoth-1.10.3/src/tstring.hpp:19,
                 from /usr/ports/work/wesnoth/src/wesnoth-1.10.3/src/config.hpp:40,
                 from /usr/ports/work/wesnoth/src/wesnoth-1.10.3/src/terrain.hpp:18,
                 from /usr/ports/work/wesnoth/src/wesnoth-1.10.3/src/map.hpp:23,
                 from /usr/ports/work/wesnoth/src/wesnoth-1.10.3/src/builder.cpp:26:
/usr/ports/work/wesnoth/src/wesnoth-1.10.3/src/foreach.hpp:9:22: error: 'boost::BOOST_FOREACH' has not been declared
make[2]: *** [src/CMakeFiles/wesnoth-game.dir/builder.cpp.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [src/CMakeFiles/wesnoth-game.dir/all] Error 2
make: *** [all] Error 2
=======> ERROR: Building '/var/ports/packages/wesnoth#1.10.3-1.pkg.tar.gz' failed.

Lets hope boost 1.51.0 fixes this, or is wesnoth 1.10.3 doing something wrong?

Regards, Danny Rawlins Romster @ freenode distro http://crux.nu

Eric Niebler — Sat, 07 Jul 2012 06:59:06 GMT

There is no fix that doesn't cause more problems than it solves, to the best of my knowledge. No changes are planned for 1.51. Simply do not #define foreach to anything and you should avoid this problem entirely.

anonymous — Thu, 12 Jul 2012 14:30:41 GMT

Someone should then update the documentation (http://www.boost.org/doc/libs/1_50_0/doc/html/foreach.html#foreach.introduction.making__literal_boost_foreach__literal__prettier) and clarify that "#define foreach should not be used". Thanks.

anonymous — Tue, 02 Oct 2012 06:17:11 GMT

Congrats, boost, you managed to break compatibility in one of the simplest-to-use libraries, and nobody gives a damn enough to at least fix the docs. Good job.

Michel Morin — Tue, 02 Oct 2012 12:07:47 GMT

The following treatment does not solve the problem, but it slightly improves the situation:

In boost/multi_index/hashed_index.hpp, change

/* Boost.Foreach compatibility */
template<
  typename KeyFromValue,typename Hash,typename Pred,
  typename SuperMeta,typename TagList,typename Category
>
inline boost::mpl::true_* boost_foreach_is_noncopyable(
  boost::multi_index::detail::hashed_index<
    KeyFromValue,Hash,Pred,SuperMeta,TagList,Category>*&,
  boost::foreach::tag)
{
  return 0;
}

into

#if !(!defined(BOOST_NO_CXX11_RVALUE_REFERENCES)                                                 \
 || BOOST_WORKAROUND(BOOST_MSVC, >= 1310) && !defined(_PREFAST_)                                 \
 || (BOOST_WORKAROUND(__GNUC__, == 4) && (__GNUC_MINOR__ <= 5) && !defined(BOOST_INTEL) &&       \
                                                                  !defined(BOOST_CLANG))         \
 || (BOOST_WORKAROUND(__GNUC__, == 3) && (__GNUC_MINOR__ >= 4) && !defined(BOOST_INTEL) &&       \
                                                                  !defined(BOOST_CLANG)))
/* Boost.Foreach compatibility */
template<
  typename KeyFromValue,typename Hash,typename Pred,
  typename SuperMeta,typename TagList,typename Category
>
inline boost::mpl::true_* boost_foreach_is_noncopyable(
  boost::multi_index::detail::hashed_index<
    KeyFromValue,Hash,Pred,SuperMeta,TagList,Category>*&,
  boost::foreach::tag)
{
  return 0;
}
#endif

and do the same thing for boost/multi_index/ordered_index.hpp, boost/multi_index/random_access_index.hpp and boost/multi_index/sequenced_index.hpp.

Eric Niebler — Wed, 03 Oct 2012 18:30:06 GMT

Can someone try defining their foreach macro like this:

#include <boost/foreach.hpp>
namespace boost
{
    namespace BOOST_FOREACH = foreach;
}
#define foreach BOOST_FOREACH

Let me know how that works for you.

linasvepstas@… — Thu, 11 Oct 2012 15:29:16 GMT

Replying to eric_niebler:

Can someone try defining their foreach macro like this:
#include <boost/foreach.hpp>
namespace boost
{
    namespace BOOST_FOREACH = foreach;
}
#define foreach BOOST_FOREACH
Let me know how that works for you.

Does not work for boost-1.49 I get: error: declaration of namespace ‘boost::BOOST_FOREACH’ conflicts with ...

/usr/local/include/boost/foreach_fwd.hpp:56:1: error: previous declaration of namespace ‘boost::BOOST_FOREACH’ here

anonymous — Thu, 11 Oct 2012 15:45:10 GMT

Anyway, I hacked around this by surrounding above with #if BOOST_VERSION != 104900 which seems to work for that one installation, and also has been reported to work with other installations (MacOS, archlinux) running boost-1.50, which break if the above is NOT done.

Original ticket: https://bugs.launchpad.net/opencog/+bug/1057640/

linasvepstas@… — Thu, 11 Oct 2012 15:53:54 GMT

To be completely clear: the following seems to work for multiple versions of boost (1.46, 1.48, 1.49, 1.50) and for multiple OS'es (MacOS, arch linux, multiple different ubuntu, RHEL4, and a cluster running old CentOS):

 #include <boost/foreach.hpp>
 #include <boost/version.hpp>
 namespace boost {
 #if BOOST_VERSION != 104900
 namespace BOOST_FOREACH = foreach;
 #endif
 } // namespace boost
 #define foreach BOOST_FOREACH

anonymous — Fri, 07 Dec 2012 12:33:54 GMT

Note from boost foreach 1.52 documentation:

I discourage this. It leads to name conflicts within the BOOST_FOREACH macro itself, where foreach is the name of a namespace

Why can't you simply rename the boost::foreach namespace into something different? These changes would be much smaller than forcing the users of boost to rename their foreach macros in thousands of source files.

Eric Niebler — Mon, 10 Dec 2012 21:43:46 GMT

Renaming the foreach namespace would be a breaking change. There are templates in the foreach namespace that end-users have specialized to make BOOST_FOREACH work with their types. All that would break if the foreach namespace changed.