Re: Getting sensible information from gdb

Newsgroups	comp.lang.c
Date	2015-10-11 22:59 -0700
References	<mvecqu$b25$1@speranza.aioe.org> <d80t0nFqg8oU1@mid.individual.net> <mvfgr5$j5f$1@speranza.aioe.org>
Message-ID	<5c9239bf-bdeb-441a-8a67-2f4ff9610348@googlegroups.com> (permalink)
Subject	Re: Getting sensible information from gdb
From	Malcolm McLean <malcolm.mclean5@btinternet.com>

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On Monday, October 12, 2015 at 6:35:45 AM UTC+1, Morten W. Petersen wrote:
>
> Should I use size_t for everything or are there cases where there
> are benefits of using a smaller type?
> 
This is the problem.
size_t was invented as type to hold an amount of memory, without
the designers realising the implications. It's not much use passing
a size_t as the element size argument to qsort unless you also
use the same type for the count argument, otherwise the interface
could still break. So size_t is used for variables which hold amounts 
of memory in bytes, variables that hold counts of items in memory,
and so, logically, also index variables.

But that's practically all the integers in the program. int just
disappears. But it's poorly-named, and it's unsigned. None of 
these values can be negative, but that's a characteristic of negative
number, they don't actually have a physical meaning, they're 
imaginary numbers, a notational convenience to make a certain
system of symbol manipulation easier. Intermediate  calculations
can and frequently do go negative. Simple code like

Point2 *zigzag;
size_t Nzigzags;
size_t i;

for(i=0;i<Nzigzags-1;i++)
  drawline(zigzag[i], zigzag[i+1]); 

fails when zigzag is empty. The only gain you get, in practice, 
is that you can declare an array of chars which takes up more than 
half the program's address space. How many programs are designed 
to operate on a single monster string?

Thread

Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-11 21:21 +0200
  Re: Getting sensible information from gdb Geoff <geoff@invalid.invalid> - 2015-10-11 14:47 -0700
    Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 00:07 +0200
      Re: Getting sensible information from gdb Geoff <geoff@invalid.invalid> - 2015-10-11 16:15 -0700
        Re: Getting sensible information from gdb James Kuyper <jameskuyper@verizon.net> - 2015-10-11 21:02 -0400
          Re: Getting sensible information from gdb Geoff <geoff@invalid.invalid> - 2015-10-11 18:55 -0700
            Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 04:04 +0200
              Re: Getting sensible information from gdb Geoff <geoff@invalid.invalid> - 2015-10-11 19:37 -0700
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 05:16 +0200
            Re: Getting sensible information from gdb James Kuyper <jameskuyper@verizon.net> - 2015-10-12 00:01 -0400
              Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 06:06 +0200
                Re: Getting sensible information from gdb James Kuyper <jameskuyper@verizon.net> - 2015-10-12 00:48 -0400
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 07:08 +0200
          Re: Getting sensible information from gdb Keith Thompson <kst-u@mib.org> - 2015-10-11 18:56 -0700
    Re: Getting sensible information from gdb Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-11 18:14 -0400
      Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 00:20 +0200
        Re: Getting sensible information from gdb James Kuyper <jameskuyper@verizon.net> - 2015-10-11 21:07 -0400
          Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 03:59 +0200
            Re: Getting sensible information from gdb Geoff <geoff@invalid.invalid> - 2015-10-11 23:21 -0700
              Re: Getting sensible information from gdb Geoff <geoff@invalid.invalid> - 2015-10-11 23:32 -0700
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 08:42 +0200
                Re: Getting sensible information from gdb Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-12 17:13 +0100
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 23:50 +0200
                Re: Getting sensible information from gdb Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-13 01:39 +0100
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-13 03:04 +0200
                Re: Getting sensible information from gdb Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-13 14:13 +0100
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-13 16:26 +0200
                Re: Getting sensible information from gdb Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-13 17:16 +0100
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-13 18:27 +0200
                Re: Getting sensible information from gdb Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-14 00:17 +0100
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-14 02:26 +0200
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-14 03:59 +0200
                Re: Getting sensible information from gdb Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-14 13:04 +0100
                Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-15 12:48 +0200
              Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 08:41 +0200
      Re: Getting sensible information from gdb Geoff <geoff@invalid.invalid> - 2015-10-11 16:18 -0700
        Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 01:22 +0200
          Re: Getting sensible information from gdb Geoff <geoff@invalid.invalid> - 2015-10-11 16:42 -0700
            Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 02:16 +0200
  Getting sensible information from gdb "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-11 18:59 -0700
    Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 04:09 +0200
      Re: Getting sensible information from gdb "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-11 19:28 -0700
        Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 04:59 +0200
          Re: Getting sensible information from gdb "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-12 07:10 -0700
            Re: Getting sensible information from gdb Rosario19 <Ros@invalid.invalid> - 2015-10-12 19:41 +0200
  Re: Getting sensible information from gdb Ian Collins <ian-news@hotmail.com> - 2015-10-12 17:59 +1300
    Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 07:36 +0200
      Re: Getting sensible information from gdb Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-11 22:59 -0700
        Re: Getting sensible information from gdb "Morten W. Petersen" <morphex@gmail.com> - 2015-10-12 08:27 +0200
          Re: Getting sensible information from gdb Johann Klammer <klammerj@NOSPAM.a1.net> - 2015-10-12 10:55 +0200
          Re: Getting sensible information from gdb Keith Thompson <kst-u@mib.org> - 2015-10-12 08:04 -0700
          Re: Getting sensible information from gdb Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-12 17:35 +0100
      Re: Getting sensible information from gdb Keith Thompson <kst-u@mib.org> - 2015-10-12 08:00 -0700
      Re: Getting sensible information from gdb James Kuyper <jameskuyper@verizon.net> - 2015-10-12 12:25 -0400

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