How to write a c++ assert macro with a varying number of informational arguments?

Question

I am trying to write a macro dbgassert similar to the standard assert. In addition to what assert does, I want to dbgassert

Answer 1

Just as a note, I was able to figure out another means to solve the trailing comma issue, in addition to @cmaster and @ds27680's solution. Since having __VA_ARGS__ leads to an extra comma, I can pack __VA_ARGS__ into a std::tuple or a function call, and use the tuple/result as a parameter of the real function. Now empty __VA_ARGS__'s won't be a problem because its packed into one valid value (i.e. either an empty tuple or the return value of a nullary function). I guess this is longer in code, but a bit more portable without involving ##.

The above two cases are shown in the dbgassert and dbgassert1 macros in the code below, respectively.

#include 
#include 
#include 
using namespace std;

template 
string print_tuple(tuple tp) {
  return ""; //print the tuple...
}

template 
void realdbgassert(tuple info,const char *msg, const char *file, int line) {
  cout << "Assertion failed! \nFile " << file << ", Line " << line << endl 
       << "  Expression: " << msg << endl
       << "  Info: " << print_tuple(info) << endl;
  std::abort();
}

#define dbgassert(EX,...) \
  (void)((EX) || (realdbgassert (std::tie(__VA_ARGS__),#EX,__FILE__, __LINE__),0))

void realdbgassert1(string info,const char *msg, const char *file, int line) {
  cout << "Assertion failed! \nFile " << file << ", Line " << line << endl 
       << "  Expression: " << msg << endl
       << "  Info: " << info << endl;
  std::abort();
}

template 
string print_info(Args ... args) {
  return "";  //print stuff
}

#define dbgassert1(EX,...) \
  (void)((EX) || (realdbgassert1 (print_info(__VA_ARGS__),#EX,__FILE__, __LINE__),0))


int main() {
  dbgassert(1>2,"right","yes"); //OK
  dbgassert(1>2,"right"); //OK
  dbgassert(1>2); //OK now
  dbgassert1(1>2); //OK too
}