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| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Getting sensible information from gdb |
| Date | 2015-10-12 17:35 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <87lhb8dozd.fsf@bsb.me.uk> (permalink) |
| References | <mvecqu$b25$1@speranza.aioe.org> <d80t0nFqg8oU1@mid.individual.net> <mvfgr5$j5f$1@speranza.aioe.org> <5c9239bf-bdeb-441a-8a67-2f4ff9610348@googlegroups.com> <mvfjr4$pem$1@speranza.aioe.org> |
"Morten W. Petersen" <morphex@gmail.com> writes:
> On 12.10.2015 07:59, Malcolm McLean wrote:
<snip>
>> [...] 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]);
for (size_t s = 1; s < Nzigzags; s++)
drawline(zizgag[s - 1], zigzag[s]);
(a) putting the declaration in the for loop make the type obvious at a
glance;
(b) starting at 1 means you never subtract from an unsigned zero;
(c) calling the counter s avoids the casual assumption that i is an int.
>> 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?
>
> I don't get this example. You mean when Nzigzags is zero?
Yes, when Nzigzags is zero the test in the loop compares i with the
largest representable size_t.
One's history can make a difference here. I started with C when int was
often 16 bits and size_t was very handy. As a result I learned how to
loop over unsigned values early on. If you are used to ints being large
enough to index any array you are likely to make, then size_t probably
looks like an anachronism with programming pitfalls lurking for the
uninitiated.
--
Ben.
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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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