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Re: sizeof object got by dereferencing uniniitalized pointer

From Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups comp.lang.c
Subject Re: sizeof object got by dereferencing uniniitalized pointer
Date 2019-12-01 09:32 -0800
Organization A noiseless patient Spider
Message-ID <867e3g6jew.fsf@linuxsc.com> (permalink)
References (9 earlier) <87v9r33211.fsf@bsb.me.uk> <861rtr8ndf.fsf@linuxsc.com> <Hb%DF.30271$s93.29962@fx19.iad> <86sgm67oyi.fsf@linuxsc.com> <esbEF.139166$Ys1.126074@fx42.iad>

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Richard Damon <Richard@Damon-Family.org> writes:

> On 11/29/19 9:10 AM, Tim Rentsch wrote:
>
>> Richard Damon <Richard@Damon-Family.org> writes:
>>
>>> I had always read the phrase from 6.5.3.4p2
>>>
>>> The sizeof operator yields the size (in bytes) of its operand, which may
>>> be an expression or the parenthesized name of a type.  The size is
>>> determined from the type of the operand.  The result is an integer.  If
>>> the type of the operand is a variable length array type, the operand is
>>> evaluated;  otherwise, the operand is not evaluated and the result is an
>>> integer constant.
>>>
>>> As referring to if the operand WAS a variable length array type, but the
>>> wording doesn't quite say that.  My guess is that is what was intended.
>>
>> Is this just supposition on your part?  Or do you have some sort
>> of confirmation based on other sources?
>
> Purely interpretation on my own part.  The way my brain works I tend to
> parse things to get intended meaning and distill down to essence.  This
> makes me bad a 'rules lawyering', i.e. detecting minute corner cases is
> rules.
>
> I've always seen the C Standard as a bit pragmatically worded, that at
> times when they couldn't get some wording exactly right, they just
> settled for good enough and left the corner cases exposed (and by
> leaving the corner cases as UB, a good implementation can still do the
> 'Right Thing')
>
> I think this is one example, it wasn't worth their effort to try and
> precisely define what needed to be evaluated to determine the type, so
> they erred on the side of letting the compiler be allowed to do more
> than needed (since it can almost always not do it by the as-if rule)
> then not let the compiler do something it needs to in order to process
> the statement and have an error in the language.

I sort of agree with you.  The determination may have been, not
that it wasn't worth their effort, but that having a more exact
but more complicated rule would have a negative ROI as far as
readers of the Standard are concerned.  Except for that one minor
difference, I think we are pretty much on the same page.

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sizeof object got by dereferencing uniniitalized pointer "V.Subramanian, India" <subramanian100in@yahoo.com> - 2019-11-28 05:20 -0800
  Re: sizeof object got by dereferencing uniniitalized pointer Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-11-28 05:37 -0800
    Re: sizeof object got by dereferencing uniniitalized pointer mark.bluemel@gmail.com - 2019-11-28 05:59 -0800
      Re: sizeof object got by dereferencing uniniitalized pointer David Brown <david.brown@hesbynett.no> - 2019-11-28 15:51 +0100
        Re: sizeof object got by dereferencing uniniitalized pointer Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-11-28 07:27 -0800
          Re: sizeof object got by dereferencing uniniitalized pointer Herbert Rosenau <nospam@hrosenau.de> - 2019-11-28 17:28 +0100
            Re: sizeof object got by dereferencing uniniitalized pointer Thiago Adams <thiago.adams@gmail.com> - 2019-11-28 08:51 -0800
              Re: sizeof object got by dereferencing uniniitalized pointer Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-28 17:36 +0000
                Re: sizeof object got by dereferencing uniniitalized pointer Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-28 16:37 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-29 01:27 +0000
                Re: sizeof object got by dereferencing uniniitalized pointer Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-28 17:47 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Richard Damon <Richard@Damon-Family.org> - 2019-11-28 21:16 -0500
                Re: sizeof object got by dereferencing uniniitalized pointer Keith Thompson <kst-u@mib.org> - 2019-11-29 00:38 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Richard Damon <Richard@Damon-Family.org> - 2019-11-29 09:03 -0500
                Re: sizeof object got by dereferencing uniniitalized pointer Keith Thompson <kst-u@mib.org> - 2019-11-29 13:15 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Keith Thompson <kst-u@mib.org> - 2019-11-29 13:38 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-29 07:09 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-29 06:10 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Richard Damon <Richard@Damon-Family.org> - 2019-11-29 11:12 -0500
                Re: sizeof object got by dereferencing uniniitalized pointer Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-12-01 09:32 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-29 07:39 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-29 22:00 +0000
                Re: sizeof object got by dereferencing uniniitalized pointer Richard Damon <Richard@Damon-Family.org> - 2019-11-29 22:40 -0500
                Re: sizeof object got by dereferencing uniniitalized pointer Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-30 11:19 +0000
                Re: sizeof object got by dereferencing uniniitalized pointer Richard Damon <Richard@Damon-Family.org> - 2019-11-30 09:01 -0500
                Re: sizeof object got by dereferencing uniniitalized pointer Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-12-01 10:28 -0800
              Re: sizeof object got by dereferencing uniniitalized pointer Richard Damon <Richard@Damon-Family.org> - 2019-11-28 12:49 -0500
                Re: sizeof object got by dereferencing uniniitalized pointer Thiago Adams <thiago.adams@gmail.com> - 2019-11-28 11:26 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Richard Damon <Richard@Damon-Family.org> - 2019-11-28 17:19 -0500
                Re: sizeof object got by dereferencing uniniitalized pointer Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-28 17:26 -0800
                Re: sizeof object got by dereferencing uniniitalized pointer Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-28 22:34 +0000
          Re: sizeof object got by dereferencing uniniitalized pointer Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-28 17:34 +0000
      You gotta wonder why people say things like this! (Was: sizeof object got by dereferencing uniniitalized pointer) gazelle@shell.xmission.com (Kenny McCormack) - 2019-11-28 17:19 +0000
    Re: sizeof object got by dereferencing uniniitalized pointer Keith Thompson <kst-u@mib.org> - 2019-11-28 14:55 -0800
      Re: sizeof object got by dereferencing uniniitalized pointer "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-30 15:28 -0800

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