Re: std::stringstream and eof() strangeness

From:

Carl Barron <cbarron413@adelphia.net>

Newsgroups:

comp.lang.c++.moderated

Date:

Fri, 25 May 2007 04:55:05 CST

Message-ID:

<250520070333415078%cbarron413@adelphia.net>

In article <1180072472.011495.72790@h2g2000hsg.googlegroups.com>,
<carl.seleborg@gmail.com> wrote:

Hello group,

I'm writing a lexer taking input from a character stream. For testing
purposes, I frequently use std::stringstream, since it's easy to get
the input I want to test my lexer with.

I expected something like this:

stringstream ss("");
assert (ss.eof());

But it turns out not to be true. However, this works:

the stream has not been accessed so eof has not occurred.

stringstream ss("");
ss.peek();
assert (ss.eof());

   the stream attempts to reach the first [non existant] char of the
stream and reports failbit for faiilure and eofbit since eof has
occurred.
     so the proper approach is to test failure. fail(),bad() functions
or either/both by conversion to bool.
    if the failbit is set (s.fail() ==true) then test for eof.

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