cet-is » fhicl » fhicl-cpp

I'm building fhicl-cpp with Clang and am getting warnings (promoted to errors by default with CAUTIOUS warning set from cetbuildtools) about operator precedence and sequencing from a few lines in parse.cc. Note that in the following the line numbers are four higher than than in source:fhiclcpp/parse.cc as I've added one additional pragma protection for Clang at the top of the file (This has zero effect on the warnings).

../fhiclcpp/parse.cc
../fhiclcpp/parse.cc:662:44: error: overloaded operator >> has higher precedence than comparison operator [-Werror,-Woverloaded-shift-op-parentheses]
         | (iter_pos >> lit("@sequence::") > noskip_qualname
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
../fhiclcpp/parse.cc:662:22: note: place parentheses around the '>>' expression to silence this warning
         | (iter_pos >> lit("@sequence::") > noskip_qualname
                     ^
            (                             )
../fhiclcpp/parse.cc:662:44: note: place parentheses around comparison expression to evaluate it first
         | (iter_pos >> lit("@sequence::") > noskip_qualname
                                           ^
                        (                                   )
../fhiclcpp/parse.cc:671:55: error: overloaded operator >> has higher precedence than comparison operator [-Werror,-Woverloaded-shift-op-parentheses]
                    | (iter_pos >> lit("@sequence::") > noskip_qualname
                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
../fhiclcpp/parse.cc:671:33: note: place parentheses around the '>>' expression to silence this warning
                    | (iter_pos >> lit("@sequence::") > noskip_qualname
                                ^
                       (                             )
../fhiclcpp/parse.cc:671:55: note: place parentheses around comparison expression to evaluate it first
                    | (iter_pos >> lit("@sequence::") > noskip_qualname
                                                      ^
                                   (                                   )
../fhiclcpp/parse.cc:692:40: error: overloaded operator >> has higher precedence than comparison operator [-Werror,-Woverloaded-shift-op-parentheses]
        | (iter_pos >> lit("@table::") > noskip_qualname
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
../fhiclcpp/parse.cc:692:21: note: place parentheses around the '>>' expression to silence this warning
        | (iter_pos >> lit("@table::") > noskip_qualname
                    ^
           (                          )
../fhiclcpp/parse.cc:692:40: note: place parentheses around comparison expression to evaluate it first
        | (iter_pos >> lit("@table::") > noskip_qualname
                                       ^
                       (                                )
../fhiclcpp/parse.cc:703:38: error: multiple unsequenced modifications to '_val' [-Werror,-Wunsequenced]
    ((iter_pos >> vp.nil    ) [ _val = phx::bind(&xvalue_dp<iter_t>, ref(in_prolog), NIL     , qi::_2, qi::_1, ref(s)) ] |
                                     ^
../fhiclcpp/parse.cc:726:41: error: overloaded operator >> has higher precedence than comparison operator [-Werror,-Woverloaded-shift-op-parentheses]
         | (iter_pos >> lit("@table::") > noskip_qualname
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
../fhiclcpp/parse.cc:726:22: note: place parentheses around the '>>' expression to silence this warning
         | (iter_pos >> lit("@table::") > noskip_qualname
                     ^
            (                          )
../fhiclcpp/parse.cc:726:41: note: place parentheses around comparison expression to evaluate it first
         | (iter_pos >> lit("@table::") > noskip_qualname
                                        ^
                        (                                )
../fhiclcpp/parse.cc:737:50: error: overloaded operator >> has higher precedence than comparison operator [-Werror,-Woverloaded-shift-op-parentheses]
                  | (iter_pos >> lit("@table::") > noskip_qualname
                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~
../fhiclcpp/parse.cc:737:31: note: place parentheses around the '>>' expression to silence this warning
                  | (iter_pos >> lit("@table::") > noskip_qualname
                              ^
                     (                          )
../fhiclcpp/parse.cc:737:50: note: place parentheses around comparison expression to evaluate it first
                  | (iter_pos >> lit("@table::") > noskip_qualname
                                                 ^
                                 (                                )

I just wanted to cross check that the the correct fix would be to wrap the Expectation Operator in parentheses, i.e

iter_pos >> ( lit("@sequence::") > noskip_qualname )

That feels right given Spirit's parser operator behaviour and what I know of fhicl grammar...

There's also the "unsequenced modifications" warning in the above:

../fhiclcpp/parse.cc:703:38: error: multiple unsequenced modifications to '_val' [-Werror,-Wunsequenced]
    ((iter_pos >> vp.nil    ) [ _val = phx::bind(&xvalue_dp<iter_t>, ref(in_prolog), NIL     , qi::_2, qi::_1, ref(s)) ] |

I'm not sure if this is spurious or not - there's a similar construct at source:fhiclcpp/parse.cc#L608 which doesn't appear to cause an error.