Question

I’m looking to have two versions of BOOST compiled into a project at the same time. Ideally they should be usable along these lines:

boost_1_36_0::boost::shared_ptr<SomeClass> someClass = new SomeClass(); boost_1_35_0::boost::regex expression('[0-9]', boost_1_35_0::boost::regex_constants::basic); 

Answer 1

I read (well scanned) through the development list discussion. There’s no easy solution. To sum up:

1. Wrapping header files in a namespace declaration

   namespace boost_1_36_0 {     #include <boost_1_36_0/boost/regex.hpp> } namespace boost_1_35_0 {     #include <boost_1_35_0/boost/shared_ptr.hpp> } 

   • Requires modifying source files
   • Doesn’t allow for both versions to be included in the same translation unit, due to the fact that macros do not respect namespaces.

2. Defining boost before including headers

   #define boost boost_1_36_0     #include <boost_1_36_0/boost/regex.hpp> #undef boost #define boost boost_1_35_0     #include <boost_1_35_0/boost/shared_ptr.hpp> #undef boost 

   • Source files can simply be compiled with -Dboost=boost_1_36_0
   • Still doesn’t address macro conflicts in a single translation unit.

   • Some internal header file inclusions may be messed up, since this sort of thing does happen.

     #if defined(SOME_CONDITION) #  define HEADER <boost/some/header.hpp> #else #  define HEADER <boost/some/other/header.hpp> #endif 

     But it may be easy enough to work around those cases.

3. Modifying the entire boost library to replace namespace boost {..} with namespace boost_1_36_0 {...} and then providing a namespace alias. Replace all BOOST_XYZ macros and their uses with BOOST_1_36_0_XYZ macros.
   • This would likely work if you were willing to put into the effort.