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Re: signed is undefined and has been since 1992 (in GCC)
- From: Robert Dewar <dewar at adacore dot com>
- To: Florian Weimer <fw at deneb dot enyo dot de>
- Cc: Olivier Galibert <galibert at pobox dot com>, Dave Korn <dave dot korn at artimi dot com>,'Andrew Haley' <aph at redhat dot com>, 'Gabriel Dos Reis' <gdr at integrable-solutions dot net>,'Andrew Pinski' <pinskia at physics dot uc dot edu>, 'gcc mailing list' <gcc at gcc dot gnu dot org>
- Date: Sat, 02 Jul 2005 19:19:29 -0400
- Subject: Re: signed is undefined and has been since 1992 (in GCC)
- References: <20050628171752.GE52889@dspnet.fr.eu.org> <SERRANO4Hqx6zrWWqGY00000275@SERRANO.CAM.ARTIMI.COM> <20050628180203.GG52889@dspnet.fr.eu.org> <42C19C5A.2040705@adacore.com> <20050628191746.GJ52889@dspnet.fr.eu.org> <42C1A318.4040407@adacore.com> <8764vt2kq3.fsf@deneb.enyo.de>
Florian Weimer wrote:
Probably it's hard to accept for hard-code C coders that a program
which generates correct machine code with all GCC versions released so
far (modulo bugs in GCC) can still be illegal C and exhibit undefined
behavior. IIRC, I needed quite some time to realize the full impact
of this distinction.
Note that even making things implementation defined does not help the
problem of learning by example from one implementation. It really is
a good idea for people programming in language X to learn language X :-)
Back in the days of Algol-60 absolutely everyone read the report. Then
we went through an era of standards which few people read (how many
fortran programmers read the fortran standard, cobol programmers
read the cobol standard, c programmers read the c standard etc). A
rather nice achievment with Ada is that the standard is indeed a
reference book that all Ada programmers have on their shelf and
even though not all have read it through, they know it is the
important ultimate reference standard of what is and what is not
allowed in valid programs, and you would be hard put to find a
professional Ada programmer who has not frequently reached for
the standard to look something up. In a big class of programmers
nearly all of whom had done professional C programming a couple
of years ago, only 2 out of 94 had held the C standard in their
hands.
It's not an easy document, but it's also not that hard, it would
be nice to promote its use more!