Re: VS2008 bug: stream extractor setting failbit on eof

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Thu, 11 Dec 2008 00:45:15 -0500

Message-ID:

<eDsCpO1WJHA.4284@TK2MSFTNGP02.phx.gbl>

"Kenneth Porter" <shiva.blacklist@sewingwitch.com> wrote in message
news:Xns9B70AC52A864Fshivawellcom@207.46.248.16

I have the following code to read from a file into a class object's
vector:

std::vector<double> data;
{
  std::ifstream f(filename);
  f.exceptions(std::ios::badbit | std::ios::failbit);
  std::copy(std::istream_iterator<double>(f), std::istream_iterator
<double>(),
            std::back_inserter(data));
}

Using Visual Studio 2008, this code is throwing in the copy operation
on end of file. It looks like down in the stream extractor it's
misinterpreting EOF as failure and setting the wrong state bit, so
this ends up throwing unexpectedly.

I believe this is actually correct outcome. istream_iterator<double>
calls operator>>(double). operator>> should set failbit if it can't
extract and convert a value of appropriate type, for any reason. In
particular, it sets failbit when called at end of file.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925