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Re: I need help understand a struct

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Andrey Tarasevich <andreytarasevich@hotmail.com> writes:

> On 1/25/2021 11:59 AM, jfbod...@gmail.com wrote:
>
>> In this case we have to use "struct _Clip *" instead of "ClipPtr"
>> to declare the pointers because the "ClipPtr" typedef name doesn't
>> exist yet.  You could get around it by forward-declaring the
>> struct tag:
>>
>>      struct _Clip; // forward declaration of the tag name,
>>                    //    type is *incomplete* at this point
>>
>>      typedef struct _Clip *ClipPtr; // you can create typedef names
>>                                     //    for incomplete types
>>
>>      struct _Clip {
>>          ClipPtr prev, next;
>>          ...
>>      };
>
> To be pedantic, the first declaration (the "forward declaration") is
> redundant in this example.  There no need to forward-declare the
> type.  You could simply do
>
>     typedef struct _Clip *ClipPtr;
>
> and this by itself would be sufficient.  [...]

Yes but....

This pattern is a dangerous habit to acquire because there are
other cases where it does make a difference.  IMO what the rules
are here is one of the backwaters of C that is best to avoid, and
an easy way to avoid it is to always separate the declaration of
a struct type from the typedef that depends on the struct.  If
that feels cumbersome then it's easy to write a macro so as not
to have to re-write the boilerplate.

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I need help understand a struct T <T@invalid.invalid> - 2021-01-18 17:01 -0800
  Re: I need help understand a struct Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-01-19 01:37 +0000
    Re: I need help understand a struct T <T@invalid.invalid> - 2021-01-18 17:41 -0800
      Re: I need help understand a struct Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-01-19 01:52 +0000
        Re: I need help understand a struct T <T@invalid.invalid> - 2021-01-18 18:03 -0800
  Re: I need help understand a struct Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-01-18 19:00 -0800
  Re: I need help understand a struct Bart <bc@freeuk.com> - 2021-01-19 11:34 +0000
    Re: I need help understand a struct Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-01-19 04:18 -0800
      Re: I need help understand a struct Bart <bc@freeuk.com> - 2021-01-19 13:01 +0000
        Re: I need help understand a struct Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-01-19 21:39 +0000
          Re: I need help understand a struct Bart <bc@freeuk.com> - 2021-01-19 23:20 +0000
            Re: I need help understand a struct Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-01-20 00:25 +0000
              Re: I need help understand a struct Bart <bc@freeuk.com> - 2021-01-20 12:42 +0000
                Re: I need help understand a struct Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-01-20 17:39 +0000
                Re: I need help understand a struct Bart <bc@freeuk.com> - 2021-01-20 19:32 +0000
                Re: I need help understand a struct Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-01-20 20:45 +0000
                Re: I need help understand a struct Bart <bc@freeuk.com> - 2021-01-21 16:12 +0000
                Re: I need help understand a struct Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-01-21 17:10 +0000
                Re: I need help understand a struct Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-01-21 11:51 -0800
                Re: I need help understand a struct Bart <bc@freeuk.com> - 2021-01-22 12:26 +0000
                Re: I need help understand a struct Kaz Kylheku <563-365-8930@kylheku.com> - 2021-01-21 20:16 +0000
                Re: I need help understand a struct Bart <bc@freeuk.com> - 2021-01-21 23:04 +0000
  Re: I need help understand a struct "jfbod...@gmail.com" <jfbode1029@gmail.com> - 2021-01-25 11:59 -0800
    Re: I need help understand a struct Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-01-25 21:18 -0800
      Re: I need help understand a struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-01-27 07:53 -0800
        Re: I need help understand a struct Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-01-27 08:35 -0800
          Re: I need help understand a struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-01-28 07:48 -0800
            Re: I need help understand a struct Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-01-28 09:25 -0800
            Re: I need help understand a struct Kaz Kylheku <563-365-8930@kylheku.com> - 2021-01-28 18:03 +0000
              Re: I need help understand a struct Guillaume <message@bottle.org> - 2021-01-28 20:46 +0100
                Re: I need help understand a struct Kaz Kylheku <563-365-8930@kylheku.com> - 2021-01-28 21:31 +0000
                Re: I need help understand a struct Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-01-29 11:15 -0800
    Re: I need help understand a struct T <T@invalid.invalid> - 2021-01-25 21:20 -0800

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