From -1392010891048495159 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,53d56717e82ab663 X-Google-Attributes: gidf78e5,public From: Ron Natalie Subject: Re: cout << null pointers Date: 2000/07/09 Message-ID: <3966405B.3BF79F21@sensor.com>#1/1 X-Deja-AN: 644038998 Content-Transfer-Encoding: 7bit Approved: Fergus Henderson , moderator of comp.std.c++ References: <39656D42.E049FCAA@ix.netcom.com> X-Accept-Language: en X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f Content-Type: text/plain; charset=x-user-defined X-Complaints-To: abuse@demon.net X-Mail2News-Path: news.demon.net!mulga.cs.mu.oz.au X-Trace: mail2news.demon.co.uk 963088253 mail2news:16953 mail2news mail2news.demon.co.uk Organization: Sensor Systems X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) Mime-Version: 1.0 Newsgroups: comp.std.c++ Paul Meyerholtz wrote: > > I have found an inconsistent output by various compilers of the following: > > char * p = 0; > cout * q = ""; > > cout << p << "\n\n"; > cout << q; > > Most compilers seem to handle "cout << q" without a problem. (But I > have heard that Visual C++ 6 fails this test). I don't think VC++ failes the test. It's pretty basic stuff. It certainly works fine in VC++ 5. > > However, the handling of "cout << p" seems to cause problems for most > computers, with results from segment faults to garbage output. Not surprising, you are invoking undefined behavior. > Why is the output of p and q different? There is a whole lot of difference between a null pointer constant (0) and an empty string literal. One is a guaranteed invalid pointer, the other is a pointer to a statically allocated array of one character with a zero in it. > > Is there anything in the standard about this? Should cout check for the > null pointer? No, the programmer should avoid giving null pointers to things that are expecting valid poitners. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html ]