Re: Result of operations on empty multimap?

From:

Pete Becker <pete@versatilecoding.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 30 Oct 2008 08:30:49 -0400

Message-ID:

<2008103008304916807-pete@versatilecodingcom>

On 2008-10-30 08:22:14 -0400, Richard Herring <junk@[127.0.0.1]> said:

In message <2008103007325843658-pete@versatilecodingcom>, Pete Becker
<pete@versatilecoding.com> writes

On 2008-10-30 07:20:58 -0400, "Moschops" <moschops@notvalid.com> said:

In moving some code from VS6 to VS2008 (bear with me, this is not a VS
question, I'm just setting context), we find new crashes that weren't there
before and we think they're related to trying an operation on a multimap
that is empty - for example,
std::multimap<double, aStructWeHaveDefined>::iterator low;
low = c.begin() ; // c is empty (i.e. c.empty()==1) but we haven't
checked for it
In VS6 these crashed did not occur, in VS2008 they do. Can anyone tell me
what is supposed to happen?

The behavior is undefined.

???

Surely the result of calling begin() on an empty multimap (or any other
std:: container, for that matter) is an iterator which compares equal
to that returned by end().

Whoops, I read it as c.first(). You're absolutely right: c.begin() is
well defined.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)