std::ifstream::exceptions() raises exception!

[SAn]

Hello!

Let us consider something like that:

#include<fstream>

int main()
{
  std::ifstream File;
  File.setstate( std::istream::eofbit );
  File.exceptions( std::istream::eofbit ); //Setting new exceptions mask – exception here!

  return EXIT_SUCCESS;
}

The problem is that at line 7 the exception of class std::ios_base::failure is thrown!

I have read here that setting new exception mask should call clear(rdstate()) : it should remove EOF flag. Also it is not documented that this function can itself raise exceptions!

What is the correct behavio(u)r of the std::ifstream::exceptions() function?

[camper]

clear(state) does not clear flags that are set in its argument. The observed behaviour is correct.

[SAn]

And what is the result of calling clear(rdstate()) ? Raising exception if ( rdstate() & exceptions() ) != 0 ?

Another question: how can I make a read loop that will read all bytes until EOF, and throw exception if file becomes inaccessible for reasons other than EOF?

I tried to remove std::istream::eofbit from exceptions mask, but the exception is still thrown when the EOF is reached. It seems that the EOF sets some other flag, not only eofbit:

std::ifstream File;
File.exceptions( std::istream::failbit | std::istream::badbit ); //No eofbit here
File.open(fileName.c_str(), std::ios_base::in | std::ios_base::binary);

do
{
	File.ignore(1); //Still raise exception when EOF is reached :(
}
while(!File.eof());

File.close();

[DrPhil_Guth]

I tried to compile and run your code, and I found that it worked perfectly well, and no exceptions are thrown.
However, I changed the filename to something that doesnt exist.
And that's where I got the exception.

I suppose the file you want to open simply doesnt exist. Maybe you should check with

if (File)

whether the file was really opened.