How to throw std::exceptions with variable messages?

Question

This is an example of what I often do when I want to add some information to an exception:

std::stringstream errMsg;
errMsg << \"Could not load config          


        

Answer 1

There are different exceptions such as runtime_error, range_error, overflow_error, logic_error, etc.. You need to pass the string into its constructor, and you can concatenate whatever you want to your message. That's just a string operation.

std::string errorMessage = std::string("Error: on file ")+fileName;
throw std::runtime_error(errorMessage);

You can also use boost::format like this:

throw std::runtime_error(boost::format("Error processing file %1") % fileName);