I have been attempting to understand the differences between compilers
          and environments when running tests on Boost Phoenix.
        
- 
              Some environments are limited in the memory available for testing and
              I have broken some large tests into smaller pieces.
            
- 
              Some of the problems experienced in testing are specific to particular
              compilers being used.
            
- 
              Some problems have occurred with several more recent compilers.
            
- 
              One problem is that I do not have access to all of the compilers used
              in the tests or by users.
              
- 
                    My system is Ubuntu 
                    12.04
                  
- 
                    I have expanded the compilers I have available to include the
                    following
                  
- 
                    gcc  4.6, 4.8.2, 4.9.0
                    & 4.9.2 (I will add 5.0 when released)
                  
- 
                    Clang  3.4, 3.5 &
                    3.6 (pre-release in the last case)
                  
 
- 
              The most difficult problems to diagnose have been some which occur
              when the compilation uses optimization.
              
- 
                    Some of the boost tests use optimization but most do not.
                  
- 
                    It is not usually documented which tests are optimized.
                  
- 
                    This means that a lot of tests run there which fail when optimized.
                  
- 
                    This has made the identification of the cause of the problems
                    more difficult.