[boost] [offtopic] Wonders of C++ syntax

Subject: [boost] [offtopic] Wonders of C++ syntax
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2014-03-05 14:31:55

Maybe this experience will be interesting to someone...

I'm currently trying to write a simple parser for function signatures
for Boost.Log and collecting different curious use cases. The parser
is supposed to extract the function name from the compiler-generated
string with the signature (i.e. BOOST_CURRENT_FUNCTION).

Now the interesting case I've stumbled upon is a conversion operator
to a function pointer:

  namespace namespc {
  struct my_class2
  {
    typedef char (*pfunc_t)(double);

    operator pfunc_t () const
    {
      std::cout << BOOST_CURRENT_FUNCTION << std::endl;
      return 0;
    }
  };
  }

I first tried to imagine how this could be written without the
typedef, but my brain broke soon enough. Then I decided to ask the
compiler, and naturally different compilers gave different answers.

GCC nicely sidestepped the problem altogether:

  namespc::my_class2::operator pfunc_t() const

MSVC was more creative:

  __cdecl namespc::my_class2::operator char (__cdecl
*)(double)(__cdecl *(void) const)(double)

Frankly, my brain can't parse this one either and it looks incorrect
to me since the function pointer type is duplicated.

So it seems, there's no syntax for expressing the operator without a
typedef, is that right? In that case, I wonder what to do with MSVC
output...