g++ __FUNCTION__ replace time

Question

Can anyone tell when g++ replaces the __FUNCTION__ \'macro\' with the string containing the function name? It seems it can replace it not until it has check the

Answer 1

Note that if you create a class, you can build a message from any number of types as you'd like which means you have a similar effect to the << operator or the format in a printf(3C). Something like this:

// make sure log remains copyable
class log
{
public:
  log(const char *function, const char *filename, int line)
  {
    f_message << function << ":" << filename << ":" << line << ": ";
  }
  ~log()
  {
    //printf("%s\n", f_message.str().c_str()); -- printf?!
    std::cerr << f_message.str() << std::endl;
  }

  log& operator () (const char *value)
  {
    f_message << value;
  }
  log& operator () (int value)
  {
    f_message << value;
  }
  // repeat with all the types you want to support in the base class
  // (should be all the basic types at least)
private:
  sstream f_message;
};

// start the magic here
log log_error(const char *func, const char *file, int line)
{
  log l(func, file, line);
  return l;
}

// NOTE: No ';' at the end here!
#define LOG_DEBUG  log_error(__func__, __FILE__, __LINE__)

// usage sample:
LOG_DEBUG("found ")(count)(" items");

Note that you could declare the << operators instead of the (). In that case the resulting usage would be something like this:

LOG_DEBUG << "found " << count << " items";

Depends which you prefer to use. I kind of like () because it protects your expressions automatically. i.e. if you want to output "count << 3" then you'd have to write:

LOG_DEBUG << "found " << (count << 3) << " items";