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Re: How do C -programmers do reliable string handling?

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On Mon, 26 Sep 2022 17:54:20 -0700
Keith Thompson <Keith.S.Thompson+u@gmail.com> wrote:
>Richard Damon <Richard@Damon-Family.org> writes:
>> On 9/26/22 2:53 PM, JiiPee wrote:
>>> On 26/09/2022 18:19, Muttley@dastardlyhq.com wrote:
>>>> Its a bit hard to accidentaly write &(str->length) rather than
>>>> str->length
>>> no, I mean if the function takes a pointer (not a variable), and we
>>> are meant to pass a pointer to the lenght. But we dont know its also 
>>> changing it.
>>> Lets *assume* that a calculation is done like this:
>>> float calculate(int round, int* lenght);
>>> And then you call it with your lenght:
>>> calculate(1110, &(str->length));
>>> thinking that its only reading the lenght. but its changing it also.
>>
>> In C, a function taking a pointer is likely going to change it, why
>> else use a pointer.
>>
>> This makes the intent fairly clear.
>
>And if the function doesn't intend to change it, it should be a
>pointer-to-const (which makes good sense if copying the value would be
>unreasonably expensive or would have side effects).

If the function takes a pointer to a struct then you can't really tell if it
will change the contents since its a lot more efficient to pass a pointer than
copy the whole structure onto the stack and for passing arrays you don't have
a choice except pass by reference (unless you embed in a struct) in which case
a pointer to const might be useful.

HOWEVER. If it requires a pointer to a primitive type then the function will
almost certainly be changing it otherwise as someone else wrote, why bother
requiring a pointer as they'll be no efficiency gains.

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Thread

How do C -programmers do reliable string handling? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-09-24 20:22 +0300
  Re: How do C -programmers do reliable string handling? Bo Persson <bo@bo-persson.se> - 2022-09-24 21:00 +0200
  Re: How do C -programmers do reliable string handling? Gawr Gura <gawrgura@mail.hololive.com> - 2022-09-24 12:29 -0700
    Re: How do C -programmers do reliable string handling? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-09-25 00:47 +0300
      Re: How do C -programmers do reliable string handling? Muttley@dastardlyhq.com - 2022-09-25 08:50 +0000
        Re: How do C -programmers do reliable string handling? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-09-25 13:37 +0300
        Re: How do C -programmers do reliable string handling? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-09-25 13:38 +0300
        Re: How do C -programmers do reliable string handling? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-25 13:34 +0200
          Re: How do C -programmers do reliable string handling? Bonita Montero <Bonita.Montero@gmail.com> - 2022-09-25 17:00 +0200
          Re: How do C -programmers do reliable string handling? Muttley@dastardlyhq.com - 2022-09-25 15:14 +0000
      Re: How do C -programmers do reliable string handling? Gawr Gura <gawrgura@mail.hololive.com> - 2022-09-25 09:22 -0700
        Re: How do C -programmers do reliable string handling? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-09-26 01:01 +0300
          Re: How do C -programmers do reliable string handling? Richard Damon <Richard@Damon-Family.org> - 2022-09-25 19:02 -0400
            Re: How do C -programmers do reliable string handling? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-09-26 07:27 +0300
              Re: How do C -programmers do reliable string handling? Muttley@dastardlyhq.com - 2022-09-26 15:19 +0000
                Re: How do C -programmers do reliable string handling? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-09-26 21:53 +0300
                Re: How do C -programmers do reliable string handling? Richard Damon <Richard@Damon-Family.org> - 2022-09-26 20:42 -0400
                Re: How do C -programmers do reliable string handling? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-26 17:54 -0700
                Re: How do C -programmers do reliable string handling? Muttley@dastardlyhq.com - 2022-09-27 09:36 +0000
                Re: How do C -programmers do reliable string handling? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-27 15:28 +0100
          Re: How do C -programmers do reliable string handling? Gawr Gura <gawrgura@mail.hololive.com> - 2022-09-25 16:34 -0700
            Re: How do C -programmers do reliable string handling? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-09-26 07:32 +0300
    Re: How do C -programmers do reliable string handling? Juha Nieminen <nospam@thanks.invalid> - 2022-09-26 08:33 +0000
      Re: How do C -programmers do reliable string handling? Paavo Helde <eesnimi@osa.pri.ee> - 2022-09-26 12:18 +0300
        Re: How do C -programmers do reliable string handling? Juha Nieminen <nospam@thanks.invalid> - 2022-09-26 09:47 +0000
      Re: How do C -programmers do reliable string handling? Gawr Gura <gawrgura@mail.hololive.com> - 2022-09-26 07:40 -0700
  Re: How do C -programmers do reliable string handling? Paavo Helde <eesnimi@osa.pri.ee> - 2022-09-24 23:04 +0300
    Re: How do C -programmers do reliable string handling? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-09-25 00:44 +0300
  Re: How do C -programmers do reliable string handling? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-09-26 02:03 -0700

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