How to throw std::exceptions with variable messages?

c++ exception exception-handling
Ben picture Ben · Sep 4, 2012 · Viewed 162.4k times · Source

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 file '" << configfile << "'";
throw std::exception(errMsg.str().c_str());

Is there a nicer way to do it?

Answer

Kerrek SB picture Kerrek SB · Sep 4, 2012

The standard exceptions can be constructed from a std::string:

#include <stdexcept>

char const * configfile = "hardcode.cfg";
std::string const anotherfile = get_file();

throw std::runtime_error(std::string("Failed: ") + configfile);
throw std::runtime_error("Error: " + anotherfile);

Note that the base class std::exception can not be constructed thus; you have to use one of the concrete, derived classes.

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