support << operator in a macro

Question

I\'d like to implement a macro which does the following:

#define report(s)   print(), throw std::runtime_error(s)

print() is a fun

Answer 1

Perhaps the following (untested!) code might be inspirational

#define report(Log) do { std::ostringstream _os; \
  _os << Log << std::flush; print(_os.str()); \
  throw std::runtime(_os.str()); } while(0)

and you might use it as report("x=" << x);

BTW, you might even pass the source location using

#define report_at(Log,Fil,Lin)  do { std::ostringstream _os; \
  _os << Fil << ":" << Lin << ": " << Log << std::flush; \
  print(_os.str()); \
  throw std::runtime(_os.str()); } while(0)

^{(to lower probability of collision with _os you might even replace all its occurrences inside the brace with _os##Lin using preprocessor concatenation)}

#define report_at_bis(Log,Fil,Lin) report_at(Log,Fil,Lin)

#define report(Log) report_at_bis(Log,__FILE__,__LINE__)

and this shows one of the cases where a macro is really useful.