How can I use the compile time constant __LINE__ in a string?

Question

I can use __LINE__ as a method parameter just fine, but I would like an easy way to use it in a function that uses strings.

For instance say I have this:

Answer 1

std::string logError(const char* file, int line, const char* msg)
{
   std::ostringstream os;
   os << file << ' ' << line << ':' << msg;
   return os.str();
}

Usage:

return logError(__FILE__, __LINE__, "my error message");

You could then make a macro for this if you were so inclined:

#define LOG_ERROR(x) logError(__FILE__, __LINE__, (x))

And then the usage would be:

return LOG_ERROR("my error message");