Re: "usual arithmetic conversions": please explain something...

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From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: "usual arithmetic conversions": please explain something...
Date	Wed, 01 Mar 2017 08:25:20 -0800
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BartC <bc@freeuk.com> writes:
> On 01/03/2017 00:59, Keith Thompson wrote:
>> BartC <bc@freeuk.com> writes:
[...]
>>> Try:
>>>
>>>               printf("%u\n", c);
>>
>> No, c is an int.
>>
>> But do try:
>>
>>     printf("%llu\n", a * b);

My mistake, I meant "%lu\n", not "%llu\n".

> It doesn't make much difference. Trying this (on a machine where long is 
> 32 bits):

Sure, if you use an incorrect format you can sometimes learn
something about the value being passed to printf, or its
representation -- but what's the point?  c is of type int, and
happens to have a negative value; printing it as if it were an
unsigned int means you're lying to the compiler, and the behavior
is undefined.  Printing the value of a * b shows you the actual
value that was converted to int.

I showed how to print the actual values with their correct types.

[...]

-- 
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"

Thread

"usual arithmetic conversions": please explain something... Lowell Gilbert <lgusenet@be-well.ilk.org> - 2017-02-28 18:33 -0500
  Re: "usual arithmetic conversions": please explain something... BartC <bc@freeuk.com> - 2017-02-28 23:45 +0000
    Re: "usual arithmetic conversions": please explain something... Keith Thompson <kst-u@mib.org> - 2017-02-28 16:59 -0800
      Re: "usual arithmetic conversions": please explain something... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-01 02:20 +0000
        Re: "usual arithmetic conversions": please explain something... Keith Thompson <kst-u@mib.org> - 2017-02-28 18:51 -0800
      Re: "usual arithmetic conversions": please explain something... BartC <bc@freeuk.com> - 2017-03-01 12:04 +0000
        Re: "usual arithmetic conversions": please explain something... Keith Thompson <kst-u@mib.org> - 2017-03-01 08:25 -0800
          Re: "usual arithmetic conversions": please explain something... BartC <bc@freeuk.com> - 2017-03-01 16:47 +0000
            Re: "usual arithmetic conversions": please explain something... Keith Thompson <kst-u@mib.org> - 2017-03-01 09:43 -0800
              Re: "usual arithmetic conversions": please explain something... BartC <bc@freeuk.com> - 2017-03-01 18:00 +0000
                Re: "usual arithmetic conversions": please explain something... Keith Thompson <kst-u@mib.org> - 2017-03-01 10:15 -0800
                Re: "usual arithmetic conversions": please explain something... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-01 19:08 +0000
          Re: "usual arithmetic conversions": please explain something... supercat@casperkitty.com - 2017-03-01 09:01 -0800
  Re: "usual arithmetic conversions": please explain something... jameskuyper@verizon.net - 2017-02-28 15:49 -0800
  Re: "usual arithmetic conversions": please explain something... Keith Thompson <kst-u@mib.org> - 2017-02-28 16:03 -0800
    Re: "usual arithmetic conversions": please explain something... Nick Bowler <nbowler@draconx.ca> - 2017-03-01 21:53 +0000
      Re: "usual arithmetic conversions": please explain something... Keith Thompson <kst-u@mib.org> - 2017-03-01 14:18 -0800
  Re: "usual arithmetic conversions": please explain something... Lowell Gilbert <lgusenet@be-well.ilk.org> - 2017-03-01 08:29 -0500
    Re: "usual arithmetic conversions": please explain something... Lowell Gilbert <lgusenet@be-well.ilk.org> - 2017-03-01 09:11 -0500
    Re: "usual arithmetic conversions": please explain something... Keith Thompson <kst-u@mib.org> - 2017-03-01 08:59 -0800
  Re: "usual arithmetic conversions": please explain something... scott@slp53.sl.home (Scott Lurndal) - 2017-03-01 14:00 +0000
    Re: "usual arithmetic conversions": please explain something... "James R. Kuyper" <jameskuyper@verizon.net> - 2017-03-01 10:58 -0500

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