Venting on C++

Lately I’ve used C++ for a tool I’ve been working on at the office. Here are some idiosyncrasies in the standard library that I’ve noticed:

I was expecting the following code to compile:

std::string f("hello.txt");
std::ifstream in_file(f);

But oh no! For some reason ifstream doesn’t have a constructor that accepts a standard C++ string. Instead I am forced to pass a const char * to the constructor, e.g.:

std::string f("hello.txt");
std::ifstream in_file(f.c_str());

I guess that’s an excellent exmple of standardisation-by-committee where one part of the committee doesn’t have a clue what the other one is doing. Pathetic, really!

Now more stuff on ifstream. One would hope that opening a non-existing file for reading would trigger some sort of exception, at the very least reading from a non-existing file shouldn’t succeed. Oh, but not so in the wonderful world of C++. The following code compiles and executes just fine even if the file (hello.txt) doesn’t exist:

std::ifstream inf("hello.txt");
std::string r;
inf >> r;
std::cout << r << std::endl;

r is unmodified by inf >> r;. Even more interestingly inf.eof() returns false. Interestingly inf.bad() returns false too. Luckily inf.good()i returns false too, so there is some way of finding out that not all is well with inf. It was also pointed out that evaluating inf itself, such as in if(inf) ..., also results in false.

Ah, now I feel much better :-)

  1. I can’t understand the reasonning behind having two methods, good() and bad() which aren’t each other’s opposites, their names certainly suggests they ought to be! It seems they are badly named, they should be called no_error_has_occured() and no_exceptional_failure_has_occured() respectively.[back]