C++ exception class with printf style string?

Question

In C++11, is there an easy (or even better, built-in) way to do something like this to do printf-style strings in an exception?

throw std::runtime_error( "Failed to open '%s' [%d]: %s", 
         filename, errno, strerror(errno) );

I know I could snprintf to a `char []' then pass the result into an exception constructor with or w/o converting to std::string first.

Just wondering if C++11 has anything better/simpler to offer.

Answer 1

Since C++11, you can construct exceptions from an std::string:

std::runtime_error("Failed to open " + std::string(filename) + std::to_string(errno));

This has the slight drawback that the constructor of std::string might throw and thus terminate your program. However, this should only come into play while handling some kind of "out of memory" exception.