CODEWITHSUNDEEP
c++c++11
james
james

Reputation: 1165

support << operator in a macro

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

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

print() is a function that I always call to print some predefined stuff. s need to support:

report("abc"); // ok
report("abc"<<100); // == report("abc100")

Apart from whatever print() outputs, Nothing else should be printed. The exception will be caught by the caller and printed there.

I find it difficult to support << in the above macro.

P.S. report() is a macro already used every where in my code base and I just want to change its behaviour. Calls like report("abc"<<100); have to be supported. define it as a function and add ';' at the end doesn't look appropriate.

Upvotes: 0

Views: 105

Answers (1)

Basile Starynkevitch
Basile Starynkevitch

Reputation: 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.

Upvotes: 2

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