[Boost-bugs] [Boost C++ Libraries] #5635: compile error due to __is_pod conflicts with clang 3.x on osx 10.6

Subject: [Boost-bugs] [Boost C++ Libraries] #5635: compile error due to __is_pod conflicts with clang 3.x on osx 10.6
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-06-23 22:41:58

#5635: compile error due to __is_pod conflicts with clang 3.x on osx 10.6
------------------------------------------------+---------------------------
 Reporter:  Dane Springmeyer <dane@…>           |       Owner:  johnmaddock
     Type:  Bugs                                |      Status:  new        
Milestone:  To Be Determined                    |   Component:  type_traits
  Version:  Boost Development Trunk             |    Severity:  Showstopper
 Keywords:                                      |  
------------------------------------------------+---------------------------
 Boost trunk no longer compiles with clang trunk on my system (mac osx
 10.6) if a header like `boost/iterator/iterator_facade.hpp` or
 `boost/filesystem/operations.hpp` is included that leverages
 `type_traits/is_pod.hpp`.

 A simple test case is:

 `clang++ -o test.o -c -I/opt/boost-trunk/include test.cpp`

 {{{
 #include <boost/iterator/iterator_facade.hpp>

 int main() {
   return 0;
 }
 }}}

 This results in:

 {{{
 In file included from test.cpp:1:
 In file included from test.cpp:1:
 In file included from /opt/boost-
 trunk/include/boost/iterator/iterator_facade.hpp:26:
 /opt/boost-trunk/include/boost/type_traits/is_pod.hpp:40:129: error: 'T'
 does not refer to a value
   ...= (::boost::type_traits::ice_or< ::boost::is_scalar<T>::value,
 ::boost::is_void<T>::value, __is_pod(T) >::value);
 ^
 /opt/boost-trunk/include/boost/type_traits/is_pod.hpp:38:20: note:
 declared here
 template <typename T> struct is_pod_impl
                    ^
 /opt/boost-trunk/include/boost/type_traits/is_pod.hpp:40:141: error: type
 name requires a specifier or qualifier
   ...= (::boost::type_traits::ice_or< ::boost::is_scalar<T>::value,
 ::boost::is_void<T>::value, __is_pod(T) >::value);
 ^
 /opt/boost-trunk/include/boost/type_traits/is_pod.hpp:40:141: error: C++
 requires a type specifier for all declarations
   ...= (::boost::type_traits::ice_or< ::boost::is_scalar<T>::value,
 ::boost::is_void<T>::value, __is_pod(T) >::value);
 ^
 /opt/boost-trunk/include/boost/type_traits/is_pod.hpp:40:141: error:
 expected ')'
 /opt/boost-trunk/include/boost/type_traits/is_pod.hpp:40:31: note: to
 match this '('
     static const bool value = (::boost::type_traits::ice_or<
 ::boost::is_scalar<T>::value, ...
                               ^
 4 errors generated.
 }}}

 See also: http://dbsgeo.com/tmp/clang-boost-error.ii


 I am seeing this with boost trunk svn r72721 and clang trunk:
 {{{
 $ clang -v
 clang version 3.0 (trunk 131789)
 Target: x86_64-apple-darwin10.7.0
 Thread model: posix
 }}}

 Developers on the #llvm irc.oftc.net channel helped advise that the reason
 is likely conflicting __is_pod definitions. To quote the details:

 {{{
 there's a horrible compatibility hack in clang to cope with gcc's
 treatment of __is_pod
 basically, __is_pod is a compiler intrinsic, unless it's defined as an
 identifier, at which point it loses its magic
 this is because gcc <4.4 defined an __is_pod struct in libstdc++ and
 gcc>=4.4 define an __is_pod intrinsic (iirc)
 type_traits/intrinsics.hpp is using __is_pod as the definition of
 BOOST_IS_POD, which would be fine, except that your translation unit also
 pulls in libstdc++ 4.2.1's bits/cpp_type_traits.h, which defines __is_pod
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5635>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.