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Re: guidelines for pointer check

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Thiago Adams <thiago.adams@gmail.com> writes:
> Do you have some style guideline for pointer checking?
>
> This is a kind of poll:
>
>
>    //Style 1
>    if (pVariable) { /*...*/ }
>
>    //Style 2
>    if (pVariable != NULL)  { /*...*/ }
>
>    //Style 3
>    if (pVariable != 0) { /*...*/ }
>
> Do you dislike one of them?
> Do you use only one of them?
> Do you use more than one?
> Other?

I prefer `if (pVariable != NULL)`.

As Stefan Ram points out, NULL requires #including a standard header,
but in a program of any complexity one of the several standard headers
that define NULL will almost certainly already be #included -- and if
not, adding `#include <stddef.h.` is easy enough.

The other styles are of course perfectly valid, and those who prefer
them are not wrong.  I prefer NULL over 0 or the implicit comparison
of Style 1 because it's more explicit and isn't likely to introduce
any potential problems.  There might be some risk that pVariable
isn't really of pointer type, and that `if (pVariable != NULL)`
still compiles because NULL is defined as 0.  Similarly, I'd compare
a char value to '\0', a floating-point value to 0.0, and I wouldn't
compare boolean value (whether _Bool or not) to anything.

I'm not entirely consistent about prefering explicit code.  For example
I don't cast the result of malloc(), preferring the implicit conversion
of void* to the appropriate target type -- partly because the cast can
cause actual problems.

My preferences are almost certainly influenced by other languages I've
used.

-- 
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

guidelines for pointer check Thiago Adams <thiago.adams@gmail.com> - 2016-12-29 12:53 -0800
  Re: guidelines for pointer check Ian Collins <ian-news@hotmail.com> - 2016-12-30 09:58 +1300
  Re: guidelines for pointer check Keith Thompson <kst-u@mib.org> - 2016-12-29 13:39 -0800
    Re: guidelines for pointer check Thiago Adams <thiago.adams@gmail.com> - 2016-12-29 15:24 -0800
      Re: guidelines for pointer check Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2016-12-29 19:05 -0500
        Re: guidelines for pointer check Thiago Adams <thiago.adams@gmail.com> - 2016-12-30 05:27 -0800
          Re: guidelines for pointer check Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-30 14:35 +0000
          Re: guidelines for pointer check supercat@casperkitty.com - 2016-12-30 10:38 -0800
        Re: guidelines for pointer check Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-02 02:28 -0800
      Re: guidelines for pointer check Keith Thompson <kst-u@mib.org> - 2016-12-29 16:19 -0800
  Re: guidelines for pointer check Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-12-29 13:58 -0800
  guidelines for pointer check asetofsymbols@gmail.com - 2016-12-30 05:35 -0800
  Re: guidelines for pointer check raltbos@xs4all.nl (Richard Bos) - 2017-01-01 10:47 +0000
  Re: guidelines for pointer check Noob <root@127.0.0.1> - 2017-01-02 14:19 +0100
    Re: guidelines for pointer check David Brown <david.brown@hesbynett.no> - 2017-01-02 14:28 +0100
      Re: guidelines for pointer check Noob <root@127.0.0.1> - 2017-01-02 17:35 +0100
        Re: Using == operator Noob <root@127.0.0.1> - 2017-01-02 19:03 +0100
          Re: Using == operator David Brown <david.brown@hesbynett.no> - 2017-01-02 23:41 +0100
            Re: Using == operator Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-01-02 14:54 -0800
              Re: Using == operator Keith Thompson <kst-u@mib.org> - 2017-01-02 15:57 -0800
                Re: Using == operator Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2017-01-03 16:31 -0500
                Re: Using == operator Keith Thompson <kst-u@mib.org> - 2017-01-03 14:06 -0800
                Re: Using == operator Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-01-03 14:44 -0800
                Re: Using == operator Keith Thompson <kst-u@mib.org> - 2017-01-03 15:05 -0800
                Re: Using == operator Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-01-04 16:42 +0000
                Re: Using == operator Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 11:46 -0800
                Re: Using == operator Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2017-01-03 21:22 -0700
                Re: Using == operator supercat@casperkitty.com - 2017-01-03 15:23 -0800
                Re: Using == operator Keith Thompson <kst-u@mib.org> - 2017-01-03 15:30 -0800
                Re: Using == operator supercat@casperkitty.com - 2017-01-03 16:02 -0800
                Re: Using == operator Keith Thompson <kst-u@mib.org> - 2017-01-03 16:30 -0800
                Re: Using == operator Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 11:26 -0800
                Re: Using == operator raltbos@xs4all.nl (Richard Bos) - 2017-01-04 09:55 +0000
                Re: Using == operator Jorgen Grahn <grahn+nntp@snipabacken.se> - 2017-01-04 16:49 +0000
                Re: Using == operator raltbos@xs4all.nl (Richard Bos) - 2017-01-10 01:28 +0000
                Re: Using == operator Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2017-01-09 19:12 -0700
                Re: Using == operator Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 09:12 -0800
                Re: Using == operator Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 09:54 -0800
              Re: Using == operator raltbos@xs4all.nl (Richard Bos) - 2017-01-03 21:08 +0000
                Re: Using == operator Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 06:44 -0800
  Re: guidelines for pointer check Anand Hariharan <mailto.anand.hariharan@gmail.com> - 2017-01-04 08:54 -0800
    Re: guidelines for pointer check Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-14 00:51 -0800

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