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From: root@MCIRPS2.MED.NYU.EDU
Newsgroups: comp.sys.sgi
Subject: uncanny casting coercion
Message-ID: <9005310035.AA05275@mcirps2.med.nyu.edu>
Date: 30 May 90 22:31:44 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 85
X-Unparsable-Date: Wed, 30 May 90 17:35:16 DSD


Some observation about typing in sgi's compiler:

Observation 1)
..............
char *fgets(s,n,stream); et al return EOF on end of file and a NULL pointer
in s . The compiler will not allow a test

if(EOF==fgets(s,n,stream)) { ...

I had to do

if((char *)EOF==fgets(s,n,stream)) { ...

The MAN says :
--------------------
DIAGNOSTICS
     If end-of-file is encountered and no characters have been read, no
     characters are transferred to s and a NULL pointer is returned.  If a
     read error occurs, such as trying to use these functions on a file that
     has not been opened for reading, a NULL pointer is returned.  Otherwise s
     is returned.

-----------------------

Should I test s or fgets ?
Why does fgets return a char * ?


Observation 2)
..............

An ANSI C char decl:

MyFunction(char *Arg)
{
if(arg[0]==NULL)CallError();
}

VS:

MyFunction(char Arg[])
{
if(arg[0]==NULL)CallError();
}

A K&R 1 char decl:

MyFunction(Arg)
char *Arg;
{
if(arg[0]==NULL)CallError();
}

MyFunction(Arg)
char Arg[];
{
if(arg[0]==NULL)CallError();
}

The ANSI form MyFunction(char *Arg) produces a compiler complaint
on the == test.


Which is the most apopropriate form to use, or am I missing somthing.  Why
should the compiler complain, or is ansi typeing of pointers, arrays,and array
pointers different in a basic way ?

Cheers,


Dan.
c




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