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Re: Warning: assignment from incompatible pointer type

From DFS <nospam@dfs.com>
Newsgroups comp.lang.c
Subject Re: Warning: assignment from incompatible pointer type
Date 2017-06-20 18:00 -0400
Organization A noiseless patient Spider
Message-ID <oic5nu$eqm$1@dont-email.me> (permalink)
References <Mlc2B.23027$xk.11193@fx39.iad> <oibl12$kg5$1@dont-email.me>

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On 6/20/2017 1:15 PM, Richard Heathfield wrote:
> On 20/06/17 17:48, DFS wrote:
>> Why am I getting this warning?
>>
>>
>> char groups[100][20];
> <snip>
>>     if (iteminarray(groups,g,dname)!=0)    //THROWS WARNING HERE
> <snip>
>>
>> int iteminarray(char *arr[], int size, char *theval)
> 
> 
> 6.3.2(3): "Except when [several exceptions that don't apply here]...an 
> expression that has type ‘‘array of type’’ is converted to an expression 
> with type ‘‘pointer to type’’ that points to the initial element of the 
> array object and is not an lvalue..."

Which reference does this come from ?


> So, because it's being used in a context that isn't one of the excepted 
> contexts, the groups array in:
> 
> if (iteminarray(groups,g,dname)!=0)    //THROWS WARNING HERE
> 
> is treated just as if it were written like this:
> 
> if (iteminarray(&groups[0],g,dname)!=0)    //THROWS WARNING HERE
> 
> Now, groups[0] has type char [20], so &groups[0] has type "pointer to 
> char[20]", or char (*)[20].
> 
> But your function is:
> 
> int iteminarray(char *arr[], int size, char *theval)
> 
> And char (*)[20] is not the same as char *arr[], which is a mere 
> shorthand for char **arr. That is, iteminarray() expects a 
> pointer-to-pointer-to-char, but what you're giving it is 
> pointer-to-array-of-20-char. These types are incompatible, hence your 
> warning.


K & R: sadistic language designers.


> It's a nuisance, I know. I've generally found that the quickest, 
> simplest fix is to throw the whole darn thing into a struct and pass 
> /that/ address around.

I haven't used structs yet in C, but I'm going to keep moving forward 
and learning.

Thanks for the answer.

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Thread

Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-20 12:48 -0400
  Re: Warning: assignment from incompatible pointer type bartc <bc@freeuk.com> - 2017-06-20 18:08 +0100
    Re: Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-21 09:32 -0400
      Re: Warning: assignment from incompatible pointer type scott@slp53.sl.home (Scott Lurndal) - 2017-06-21 13:48 +0000
  Re: Warning: assignment from incompatible pointer type Richard Heathfield <rjh@cpax.org.uk> - 2017-06-20 18:15 +0100
    Re: Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-20 18:00 -0400
      Re: Warning: assignment from incompatible pointer type "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-20 18:47 -0400
        Re: Warning: assignment from incompatible pointer type bartc <bc@freeuk.com> - 2017-06-21 00:10 +0100
        Re: Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-20 19:56 -0400
  Re: Warning: assignment from incompatible pointer type "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-20 13:23 -0400
    Re: Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-20 18:59 -0400
  Re: Warning: assignment from incompatible pointer type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-20 19:23 +0100
    Re: Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-20 18:59 -0400
      Re: Warning: assignment from incompatible pointer type Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2017-06-20 19:46 -0400
      Re: Warning: assignment from incompatible pointer type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-21 02:05 +0100
        Re: Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-20 21:37 -0400
          Re: Warning: assignment from incompatible pointer type Richard Heathfield <rjh@cpax.org.uk> - 2017-06-21 09:25 +0100
          Re: Warning: assignment from incompatible pointer type David Brown <david.brown@hesbynett.no> - 2017-06-21 13:35 +0200
            Re: Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-21 22:30 -0400
              Re: Warning: assignment from incompatible pointer type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-22 11:03 +0100
              Re: Warning: assignment from incompatible pointer type bartc <bc@freeuk.com> - 2017-06-22 11:10 +0100
                Re: Warning: assignment from incompatible pointer type bartc <bc@freeuk.com> - 2017-06-22 11:42 +0100
                Re: Warning: assignment from incompatible pointer type David Brown <david.brown@hesbynett.no> - 2017-06-22 13:49 +0200
                Re: Warning: assignment from incompatible pointer type bartc <bc@freeuk.com> - 2017-06-22 14:40 +0100
                Re: Warning: assignment from incompatible pointer type bartc <bc@freeuk.com> - 2017-06-22 17:00 +0100
                Re: Warning: assignment from incompatible pointer type David Brown <david.brown@hesbynett.no> - 2017-06-22 20:08 +0200
                Re: Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-22 15:46 -0400
                Re: Warning: assignment from incompatible pointer type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-22 14:00 +0100
                Re: Warning: assignment from incompatible pointer type bartc <bc@freeuk.com> - 2017-06-22 14:38 +0100
                Re: Warning: assignment from incompatible pointer type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-22 17:26 +0100
                Re: Warning: assignment from incompatible pointer type Keith Thompson <kst-u@mib.org> - 2017-06-22 10:21 -0700
                Re: Warning: assignment from incompatible pointer type bartc <bc@freeuk.com> - 2017-06-22 18:26 +0100
                Re: Warning: assignment from incompatible pointer type David Brown <david.brown@hesbynett.no> - 2017-06-22 20:41 +0200
                Re: Warning: assignment from incompatible pointer type Richard Heathfield <rjh@cpax.org.uk> - 2017-06-22 19:59 +0100
                Re: Warning: assignment from incompatible pointer type Keith Thompson <kst-u@mib.org> - 2017-06-22 12:28 -0700
          Re: Warning: assignment from incompatible pointer type Jerry Stuckle <jstucklex@attglobal.net> - 2017-06-21 09:49 -0400
            Re: Warning: assignment from incompatible pointer type DFS <nospam@dfs.com> - 2017-06-21 10:36 -0400
              Re: Warning: assignment from incompatible pointer type Jerry Stuckle <jstucklex@attglobal.net> - 2017-06-21 14:15 -0400
          Re: Warning: assignment from incompatible pointer type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-21 15:10 +0100

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