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Groups > comp.lang.c > #123694

Re: Some kind of contextual modulo operator?

From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: Some kind of contextual modulo operator?
Date 2017-12-01 12:09 -0800
Organization None to speak of
Message-ID <lnpo7yw6q0.fsf@kst-u.example.com> (permalink)
References (6 earlier) <1679454a-2d88-4821-be92-a73dba4d4d75@googlegroups.com> <jFSTB.60693$1M.45530@fx32.am4> <bfeUB.110929$au1.21996@fx45.am4> <sufUB.3600$bx.564@fx42.iad> <4%fUB.65585$M61.56524@fx38.am4>

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bartc <bc@freeuk.com> writes:
> On 01/12/2017 16:32, Scott Lurndal wrote:
>> bartc <bc@freeuk.com> writes:
>>> A further point about malloc: I generally call it as a foreign function,
>>> with its parameter defined as either a 32-bit or 64-bit signed integer.
>> 
>> MALLOC(3)                  Linux Programmer's Manual                 MALLOC(3)
[...]
>>         #include <stdlib.h>
[...]
>
> That's helpful.
>
> I want to call it from ASM, so is that size_t type 32 bits, 64, or 
> something else?

As you know, it varies from one implementation to another.  If you're
calling it from ASM, it's up to you to figure it out.  If you need help
with that, just ask.  (I don't believe you do.)

> Or do I have to go delving into the usual jungle of C header files to 
> find out? Which I suspect won't be very enlightening.
>
> That size_t might be unsigned is not relevant to the use of malloc as 
> I've mentioned.

"might be"?  size_t *is* an unsigned type.  Of course you know that.

Apart from determining the size, you were faced with a choice:
incorrectly treat it as a signed type, or correctly treat it as
an unsigned type.  You chose to do it the wrong way.  Perhaps your
deliberate mistake doesn't have any serious consequences, but I'm
at a loss to understand your reasoning.

You mention later in this thread that "If you don't know C, you might
not know that size_t is unsigned".  Of what possible relevance is that?
Do you expect people who don't know C, and who can't be bothered to find
out whether size_t is signed or unsigned, to be writing ASM code that
calls malloc()?

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Thread

Some kind of contextual modulo operator? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-11-29 10:41 -0800
  Re: Some kind of contextual modulo operator? jameskuyper@verizon.net - 2017-11-29 11:12 -0800
    Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-11-29 19:22 +0000
      Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-11-29 19:43 +0000
        Re: Some kind of contextual modulo operator? jameskuyper@verizon.net - 2017-11-29 12:33 -0800
          Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-11-29 23:22 +0000
            Re: Some kind of contextual modulo operator? jameskuyper@verizon.net - 2017-11-29 20:53 -0800
              Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-11-30 12:17 +0000
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-01 15:08 +0000
                Re: Some kind of contextual modulo operator? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-12-01 07:31 -0800
                Re: Some kind of contextual modulo operator? scott@slp53.sl.home (Scott Lurndal) - 2017-12-01 16:32 +0000
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-01 17:07 +0000
                Re: Some kind of contextual modulo operator? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-12-01 09:15 -0800
                Re: Some kind of contextual modulo operator? scott@slp53.sl.home (Scott Lurndal) - 2017-12-01 18:14 +0000
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-01 19:03 +0000
                Re: Some kind of contextual modulo operator? scott@slp53.sl.home (Scott Lurndal) - 2017-12-01 20:54 +0000
                Re: Some kind of contextual modulo operator? Keith Thompson <kst-u@mib.org> - 2017-12-01 12:09 -0800
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-01 21:56 +0000
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-01 23:11 +0000
                Re: Some kind of contextual modulo operator? supercat@casperkitty.com - 2017-12-01 15:16 -0800
                Re: Some kind of contextual modulo operator? David Brown <david.brown@hesbynett.no> - 2017-12-02 17:09 +0100
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-02 19:42 +0000
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-03 09:16 +1300
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-02 22:06 +0000
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-03 11:20 +1300
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-03 00:01 +0000
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-03 13:55 +1300
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-03 02:14 +0000
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-03 16:13 +1300
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-03 12:28 +0000
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-03 14:26 +0000
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-04 10:49 +1300
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-04 10:38 +1300
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-03 23:00 +0000
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-04 12:10 +1300
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-03 23:33 +0000
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-04 13:18 +1300
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-04 12:19 +0000
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-05 07:58 +1300
                Re: Some kind of contextual modulo operator? David Brown <david.brown@hesbynett.no> - 2017-12-04 00:30 +0100
                Packed structs (was Re: Some kind of contextual modulo operator?) scott@slp53.sl.home (Scott Lurndal) - 2017-12-04 15:02 +0000
                Re: Packed structs (was Re: Some kind of contextual modulo operator?) David Brown <david.brown@hesbynett.no> - 2017-12-04 16:34 +0100
                Re: Packed structs (was Re: Some kind of contextual modulo operator?) Keith Thompson <kst-u@mib.org> - 2017-12-04 09:23 -0800
                Re: Packed structs (was Re: Some kind of contextual modulo operator?) scott@slp53.sl.home (Scott Lurndal) - 2017-12-04 18:31 +0000
                Re: Packed structs (was Re: Some kind of contextual modulo operator?) supercat@casperkitty.com - 2017-12-04 15:37 -0800
                Re: Some kind of contextual modulo operator? supercat@casperkitty.com - 2017-12-04 08:39 -0800
                Re: Some kind of contextual modulo operator? "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2017-12-03 18:13 -0800
                Re: Some kind of contextual modulo operator? Ian Collins <ian-news@hotmail.com> - 2017-12-03 14:50 +1300
                Re: Some kind of contextual modulo operator? scott@slp53.sl.home (Scott Lurndal) - 2017-12-04 15:00 +0000
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-04 15:53 +0000
                Re: Some kind of contextual modulo operator? scott@slp53.sl.home (Scott Lurndal) - 2017-12-04 18:26 +0000
                Re: Some kind of contextual modulo operator? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-12-04 10:34 -0800
                Re: Some kind of contextual modulo operator? David Brown <david.brown@hesbynett.no> - 2017-12-03 19:40 +0100
                Re: Some kind of contextual modulo operator? David Kleinecke <dkleinecke@gmail.com> - 2017-12-03 11:35 -0800
                Re: Some kind of contextual modulo operator? scott@slp53.sl.home (Scott Lurndal) - 2017-12-04 14:59 +0000
                Re: Some kind of contextual modulo operator? Keith Thompson <kst-u@mib.org> - 2017-12-01 08:56 -0800
                Re: Some kind of contextual modulo operator? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-12-01 08:58 -0800
                Re: Some kind of contextual modulo operator? scott@slp53.sl.home (Scott Lurndal) - 2017-12-01 18:16 +0000
                Re: Some kind of contextual modulo operator? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-12-01 10:28 -0800
                Re: Some kind of contextual modulo operator? David Brown <david.brown@hesbynett.no> - 2017-12-01 20:19 +0100
                Re: Some kind of contextual modulo operator? Gareth Owen <gwowen@gmail.com> - 2017-12-01 22:22 +0000
                Re: Some kind of contextual modulo operator? jameskuyper@verizon.net - 2017-12-01 07:49 -0800
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-01 16:54 +0000
                Re: Some kind of contextual modulo operator? jameskuyper@verizon.net - 2017-12-01 09:34 -0800
                Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-12-01 18:48 +0000
                Re: Some kind of contextual modulo operator? jameskuyper@verizon.net - 2017-12-01 11:27 -0800
      Re: Some kind of contextual modulo operator? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-11-29 12:17 -0800
        Re: Some kind of contextual modulo operator? bartc <bc@freeuk.com> - 2017-11-30 12:27 +0000
          Re: Some kind of contextual modulo operator? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2017-11-30 06:11 -0800
    Re: Some kind of contextual modulo operator? "James R. Kuyper" <jameskuyper@verizon.net> - 2017-11-29 15:02 -0500
  Some kind of contextual modulo operator? mcheung63@gmail.com - 2017-12-08 23:20 -0800

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