Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!columbia!cubmol!ping
From: ping@cubmol.bio.columbia.edu (Shiping Zhang)
Newsgroups: comp.lang.c
Subject: Re: Help on casting arrays
Keywords: casts
Message-ID: <1990Feb1.144935.8651@cubmol.bio.columbia.edu>
Date: 1 Feb 90 14:49:35 GMT
References: <931@christopher-robin.cs.bham.ac.uk> <1990Jan31.165428.2538@cubmol.bio.columbia.edu>
Reply-To: ping@cubmol.bio.columbia.edu (Shiping Zhang)
Organization: Dept. of Biology, Columbia Univ., New York, NY
Lines: 43

In article <1990Jan31.165428.2538@cubmol.bio.columbia.edu> ping@cubmol.bio.columbia.edu (Shiping Zhang) writes:
>In article <931@christopher-robin.cs.bham.ac.uk> cjr@uk.ac.bham.cs (Chris Ridd <RiddCJ>) writes:
>>I have the following declarations in an image enhancing program:
  
>>typedef unsigned char u_char;
>>char ang[512][512];
> ^^^^
>ang is declared as char instead u_char.
 
>>void imgsave(char *filename, u_char img[512][512])
>>{
>>...
>>}
  
>>  imgsave("filename", ang);
  
>>The GCC compiler gives (correctly) a warning on the imgsave call, saying
>>incompatible pointer types (or something similar).  What should the cast be
>>to correct this?  I have tried:
>>(u_char (*)[512][512])ang,
>>((u_char *)[512][512])ang,
>>     etc...
  
 
>The casting should be following:
 
> u_char (*img)[512]

Someone pointed out to me that it is a declare instead of cast.
He is right.  The cast should be

    (u_char (*)[512])img

Sorry for the wrong information.

By the way, the problem of the original poster is probably caused
by declaring ang as char instead u_char, unless it is the auther's
intention. It is not necessary to cast ang when it is used as the
second argument of imgsave() if the declaration is consistant.

>-ping

-ping