Re: setting pointers to NULL and testing question.

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NNTP-Posting-Date	Fri, 17 Jun 2016 00:13:30 -0500
From	Gareth Owen <gwowen@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: setting pointers to NULL and testing question.
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Date	Fri, 17 Jun 2016 06:13:30 +0100
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Tim Rentsch <txr@alumni.caltech.edu> writes:

>> Counter:
>> If an uninitialized variable is used before being initialized, in a way
>> that the compiler can't catch - it will cause problems.  [...]
>
> There are no such cases.  

There are no cases a compiler *can't* catch.  There are cases that
compilers don't catch[0].  Most notably, if a pointer to an uninitialized
variable is passed to a function defined in a different translation
unit.

> A conservative analysis can catch every situation where a variable
> might be used before being given an initial value, provided of course
> that we are willing to tolerate some false positives.

A sufficiently good compiler .... 
Nevertheless, no existing compiler known to me does such an exhaustive search.

[0] There are also cases that a single compiler sometimes catches,
    depending on which compiler flags you use. Optimisations often catch extra things.

Thread

setting pointers to NULL and testing question. G G <gdotone@gmail.com> - 2016-06-12 16:21 -0700
  Re: setting pointers to NULL and testing question. Richard Heathfield <rjh@cpax.org.uk> - 2016-06-13 00:50 +0100
    Re: setting pointers to NULL and testing question. G G <gdotone@gmail.com> - 2016-06-12 17:03 -0700
    Re: setting pointers to NULL and testing question. Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-06-12 20:25 -0600
      Re: setting pointers to NULL and testing question. James Kuyper <jameskuyper@verizon.net> - 2016-06-12 22:57 -0400
        Re: setting pointers to NULL and testing question. Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-06-13 10:03 -0600
          Re: setting pointers to NULL and testing question. Tim Rentsch <txr@alumni.caltech.edu> - 2016-06-15 14:43 -0700
      Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-13 08:06 -0700
        Re: setting pointers to NULL and testing question. Richard Damon <Richard@Damon-Family.org> - 2016-06-16 08:27 -0400
          Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-16 06:27 -0700
            Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-16 07:31 -0700
            Re: setting pointers to NULL and testing question. Richard Damon <Richard@Damon-Family.org> - 2016-06-18 13:39 -0400
              Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-18 11:37 -0700
                Re: setting pointers to NULL and testing question. Richard Damon <Richard@Damon-Family.org> - 2016-06-18 17:17 -0400
                Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-18 17:22 -0700
      Re: setting pointers to NULL and testing question. James Kuyper <jameskuyper@verizon.net> - 2016-06-13 14:10 -0400
        Re: setting pointers to NULL and testing question. Keith Thompson <kst-u@mib.org> - 2016-06-13 11:28 -0700
        Re: setting pointers to NULL and testing question. Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-06-13 12:31 -0600
    Re: setting pointers to NULL and testing question. Keith Thompson <kst-u@mib.org> - 2016-06-12 19:38 -0700
      Re: setting pointers to NULL and testing question. Richard Heathfield <rjh@cpax.org.uk> - 2016-06-13 07:35 +0100
    Re: setting pointers to NULL and testing question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-13 11:40 +0100
      Re: setting pointers to NULL and testing question. BartC <bc@freeuk.com> - 2016-06-13 11:56 +0100
        Re: setting pointers to NULL and testing question. Martin Shobe <mashobe9@gmail.com> - 2016-06-13 06:22 -0500
          Re: setting pointers to NULL and testing question. BartC <bc@freeuk.com> - 2016-06-13 12:39 +0100
            Re: setting pointers to NULL and testing question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-13 15:22 +0100
              Re: setting pointers to NULL and testing question. BartC <bc@freeuk.com> - 2016-06-13 17:34 +0100
                Re: setting pointers to NULL and testing question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-13 19:31 +0100
                Re: setting pointers to NULL and testing question. BartC <bc@freeuk.com> - 2016-06-13 20:17 +0100
                Re: setting pointers to NULL and testing question. Keith Thompson <kst-u@mib.org> - 2016-06-13 12:47 -0700
                Re: setting pointers to NULL and testing question. Tim Rentsch <txr@alumni.caltech.edu> - 2016-06-15 16:44 -0700
                Re: setting pointers to NULL and testing question. Keith Thompson <kst-u@mib.org> - 2016-06-15 17:20 -0700
      Re: setting pointers to NULL and testing question. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-06-13 04:01 -0700
        Re: setting pointers to NULL and testing question. Tim Rentsch <txr@alumni.caltech.edu> - 2016-06-16 12:57 -0700
      Re: setting pointers to NULL and testing question. Richard Heathfield <rjh@cpax.org.uk> - 2016-06-13 12:18 +0100
        Re: setting pointers to NULL and testing question. David Brown <david.brown@hesbynett.no> - 2016-06-13 14:01 +0200
          Re: setting pointers to NULL and testing question. Richard Heathfield <rjh@cpax.org.uk> - 2016-06-13 14:15 +0100
            Re: setting pointers to NULL and testing question. David Brown <david.brown@hesbynett.no> - 2016-06-13 15:37 +0200
              Re: setting pointers to NULL and testing question. Richard Heathfield <rjh@cpax.org.uk> - 2016-06-13 14:48 +0100
        Re: setting pointers to NULL and testing question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-13 15:43 +0100
  Re: setting pointers to NULL and testing question. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-06-12 17:54 -0700
  Re: setting pointers to NULL and testing question. John Bode <jfbode1029@gmail.com> - 2016-06-14 08:36 -0700
    Re: setting pointers to NULL and testing question. Richard Heathfield <rjh@cpax.org.uk> - 2016-06-14 16:41 +0100
    Re: setting pointers to NULL and testing question. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-06-14 09:01 -0700
    Re: setting pointers to NULL and testing question. "James R. Kuyper" <jameskuyper@verizon.net> - 2016-06-14 13:25 -0400
      Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-14 10:48 -0700
        Re: setting pointers to NULL and testing question. Ian Collins <ian-news@hotmail.com> - 2016-06-15 08:24 +1200
          Re: setting pointers to NULL and testing question. "James R. Kuyper" <jameskuyper@verizon.net> - 2016-06-14 16:57 -0400
            Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-14 14:29 -0700
              Re: setting pointers to NULL and testing question. BartC <bc@freeuk.com> - 2016-06-14 22:41 +0100
                Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-14 15:16 -0700
                Re: setting pointers to NULL and testing question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-15 00:25 +0100
                Re: setting pointers to NULL and testing question. Keith Thompson <kst-u@mib.org> - 2016-06-14 16:58 -0700
                Re: setting pointers to NULL and testing question. David Brown <david.brown@hesbynett.no> - 2016-06-15 09:28 +0200
                Re: setting pointers to NULL and testing question. Keith Thompson <kst-u@mib.org> - 2016-06-15 09:57 -0700
              Re: setting pointers to NULL and testing question. David Brown <david.brown@hesbynett.no> - 2016-06-15 09:23 +0200
                Re: setting pointers to NULL and testing question. Richard Heathfield <rjh@cpax.org.uk> - 2016-06-15 08:35 +0100
                Re: setting pointers to NULL and testing question. Richard Heathfield <rjh@cpax.org.uk> - 2016-06-15 08:37 +0100
                Re: setting pointers to NULL and testing question. David Brown <david.brown@hesbynett.no> - 2016-06-15 10:42 +0200
                Re: setting pointers to NULL and testing question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-15 13:28 +0100
                Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-15 11:41 -0700
                Re: setting pointers to NULL and testing question. raltbos@xs4all.nl (Richard Bos) - 2016-06-15 19:43 +0000
                Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-15 13:09 -0700
                Re: setting pointers to NULL and testing question. David Brown <david.brown@hesbynett.no> - 2016-06-15 22:31 +0200
                Re: setting pointers to NULL and testing question. Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-06-15 17:11 -0400
                Re: setting pointers to NULL and testing question. raltbos@xs4all.nl (Richard Bos) - 2016-06-18 20:44 +0000
                Re: setting pointers to NULL and testing question. Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-06-18 17:20 -0400
        Re: setting pointers to NULL and testing question. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-06-14 23:22 -0700
          Re: setting pointers to NULL and testing question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-15 13:23 +0100
      Re: setting pointers to NULL and testing question. John Bode <jfbode1029@gmail.com> - 2016-06-20 13:36 -0700
    Re: setting pointers to NULL and testing question. Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-06-14 14:59 -0400
      Re: setting pointers to NULL and testing question. "James R. Kuyper" <jameskuyper@verizon.net> - 2016-06-14 15:17 -0400
      Re: setting pointers to NULL and testing question. Richard Heathfield <rjh@cpax.org.uk> - 2016-06-14 20:25 +0100
      Re: setting pointers to NULL and testing question. Tim Rentsch <txr@alumni.caltech.edu> - 2016-06-15 19:48 -0700
        Re: setting pointers to NULL and testing question. Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-06-15 23:25 -0400
          Re: setting pointers to NULL and testing question. James Kuyper <jameskuyper@verizon.net> - 2016-06-16 12:11 -0400
            Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-16 09:25 -0700
            Re: setting pointers to NULL and testing question. Tim Rentsch <txr@alumni.caltech.edu> - 2016-06-16 21:46 -0700
              Re: setting pointers to NULL and testing question. Gareth Owen <gwowen@gmail.com> - 2016-06-17 06:13 +0100
                Re: setting pointers to NULL and testing question. Robert Wessel <robertwessel2@yahoo.com> - 2016-06-17 02:03 -0500
                Re: setting pointers to NULL and testing question. Martin Shobe <mashobe9@gmail.com> - 2016-06-17 07:07 -0500
                Re: setting pointers to NULL and testing question. supercat@casperkitty.com - 2016-06-17 03:18 -0700
                Re: setting pointers to NULL and testing question. James Kuyper <jameskuyper@verizon.net> - 2016-06-17 09:16 -0400
                Re: setting pointers to NULL and testing question. Tim Rentsch <txr@alumni.caltech.edu> - 2016-06-21 11:03 -0700
                Re: setting pointers to NULL and testing question. Tim Rentsch <txr@alumni.caltech.edu> - 2016-06-21 10:58 -0700
              Re: setting pointers to NULL and testing question. Keith Thompson <kst-u@mib.org> - 2016-06-21 11:28 -0700
          Re: setting pointers to NULL and testing question. Tim Rentsch <txr@alumni.caltech.edu> - 2016-06-16 21:39 -0700

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