dangling if and macro

Question

I'm in the need to get rid of warnings, one of it is a -Wdangling-else. It notes a dangling if inside the following macro definition:

#define FOR_EACH_REF(var, container) \
    if(bool _cont = true) \
      for(our::remove_reference<decltype(container)>::type::iterator _it = (container).begin(); _it != (container).end() && _cont; ++_it) \
        if((_cont = false)) {} else \
          for(our::remove_reference<decltype(container)>::type::value_type& var = *_it; !_cont; _cont = true)

I must admit, I do not really get into this macro and thus do not know, how to resolve this warning.

Could anyone help me with an explanation on how to avoid the dangling else?

Answer 1

You might reverse the condition to avoid to have empty if-block and so problematic else:

#define FOR_EACH_REF(var, container) \
    if (bool _cont = true) \
      for(our::remove_reference<decltype(container)>::type::iterator _it = (container).begin(); _it != (container).end() && _cont; ++_it) \
        if(!(_cont = false)) \
          for(our::remove_reference<decltype(container)>::type::value_type& var = *_it; !_cont; _cont = true)

Since C++11, it would even be easy to write:

#define FOR_EACH_REF(var, container) for (auto& var : container)