• devel/boost was outdated
• there was big number (~50) of ports depending on outdated devel/boost

• The patch for updating devel/boost from 1.34 to 1.37 is ready.
• The issue for updating to 1.37 is filed (ports/129226).
• Alexander Churanov asked for taking maintainership of devel/boost.
• All ports that directly depend on boost are identified.
• The ports will break if devel/boost is updated to 1.37 are found. Here's the list (please keep it up to date):

• Remove detailed reporting on SIGBUS, SIGCHLD, SIGSEGV and SIGILL in Boost.Test. Since detailed information is not available on FreeBSD 6x. For example, only the fact SIGILL was caught will be reported, without any details.
• Remove support for long double from Boost.Math, because it only presents in FreeBSD-CURRENT.

1. Most common and easiest one

somefile.cc:1234: error: reference to 'exception' is ambiguous
/usr/include/c++/4.2/exception:57: error: candidates are: class std::exception
/usr/local/include/boost/exception/exception.hpp:177: error:                 class boost::exception

Resolution (std::exception is most likely to be used of those two):

- catch(exception &e)
+ catch(std::exception &e)

2. Actually, only related to rblibtorrent, but affects at least 3 ports (net-p2p/rblibtorrent, net-p2p/rblibtorrent-devel, net-p2p/deluge05 (which uses bundled rblibtorrent; net-p2p/deluge does too, but it already has this fix))

somefile.cc:1234: error: 'condition' in namespace 'boost' does not name a type

In newer boost, `condition' is not a class, but a typedef alias to condition_variable_any. It resides in the same include as before (boost/thread/condition.hpp), but it's no more included from other boost includes, so it's to be included explicitly:

+#include <boost/thread/condition.hpp>

3. An example of tougher one. The cause is change in boost class layout.

somefile.cc:1234: error: 'lookup_errno' is not a member of 'fs'
somefile.cc:1234: error: 'filesystem_path_error' was not declared in this scope

The fix may be available in newer release of software in question or in it's VCS. The changes in boost are not (at least for what I've seen up to now) severe enough to require significant changes in program logic, but you'll have to browse through boost includes to know what has been changed to what. For example, this error is from print/lyx05 (fs is a namespace-alias to boost::filesystem here). Also http://codesearch.google.com is really helpful for finding related code snippets.

 		boost::throw_exception(
-			filesystem_path_error(
+			basic_filesystem_error<path>(
 				"boost::filesystem::copy_file",
 				source, target,
-				fs::lookup_errno(errno)));
+				boost::system::error_code(errno, boost::system::get_system_category())));

4.

In file included from /usr/local/include/boost/function/detail/maybe_include.hpp:18,
                 from /usr/local/include/boost/function/detail/function_iterate.hpp:14,
                 from /usr/local/include/boost/preprocessor/iteration/detail/iter/forward1.hpp:52,
                 from /usr/local/include/boost/function.hpp:64,
                 ...
/usr/local/include/boost/function/function_template.hpp:965: error: declaration of `class R'
/usr/local/include/boost/function/function_template.hpp:654: error:  shadows template parm `class R'
...
somefile.cc:1234: error: expected `}' at end of input

That's the bug in boost/function/function_template.hpp, affcted boost versions ⇐ 1.38.0. The patch (obtained from boost SVN):

--- boost/function/function_template.hpp.orig	2008-10-16 17:21:50.000000000 +0400
+++ boost/function/function_template.hpp	2009-03-25 04:12:15.000000000 +0300
@@ -950,10 +950,10 @@
           f.vtable->manager(f.functor, this->functor,
                             boost::detail::function::move_functor_tag);
 		  f.vtable = 0;
-#if !defined(BOOST_NO_EXCEPTIONS)      
         } else {
           clear();
         }
+#if !defined(BOOST_NO_EXCEPTIONS)      
       } catch (...) {
         vtable = 0;
         throw;

5. Just as a note: many programs have boost (or some part of it) bundled - may just use it if the fix seem complex enough.