SWIG parser error

Question

I have following header file.

#include 

namespace A {
namespace B {

    struct Msg {
        std::string id;
        std::string msg;

        M         


        

Answer 1

Although SWIG 3.x added limited decltype support it looks like the case you have is unsupported currently. (See decltype limitations)

I think the best you'll get for now is to surround the offending code in preprocessor macros to hide it, e.g.:

#include 

namespace A {
namespace B {

    struct Msg {
        std::string id;
        std::string msg;

        Msg(std::string new_id, std::string new_msg)
        : id(new_id), msg(new_msg)
        {
        }
    };

    template
    class ID {
    public:
#ifndef SWIG
        template
        auto get(TOBJ parent) -> decltype(parent.id()) {
            return parent.id();
        }
#endif
    };   
} // namespace B
} // namespace A

---

If you can't edit the file like that for whatever reason there are two options:

1. Don't use %include with the header file that doesn't parse. Instead write something like:

   %{
   #include "header.h" // Not parsed by SWIG here though
   %}
   
   namespace A {
   namespace B {
   
       struct Msg {
           std::string id;
           std::string msg;
   
           Msg(std::string new_id, std::string new_msg)
           : id(new_id), msg(new_msg)
           {
           }
       };
   
   } // namespace B
   } // namespace A
   
   in your .i file, which simply tells SWIG about the type you want to wrap and glosses over the one that doesn't work.
   

2. Alternatively get creative with the pre-processor and find a way to hide it using a bodge, inside your .i file you could write something like:

   #define auto // \
   void ignore_me();
   
   %ignore ignore_me;
   

   Another similar bodge would be to hide the contents of decltype with:

   #define decltype(x) void*
   

   Which just tells SWIG to assume all decltype usage is a void pointer. (Needs SWIG 3.x and could be combined with %ignore which ought to do the ignore, or a typemap to really fix it)