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From: norm@oglvee.UUCP (Norman Joseph)
Newsgroups: comp.sys.ibm.pc.programmer
Subject: Re: `C' type question...
Message-ID: <564@oglvee.UUCP>
Date: 10 Jul 90 15:12:14 GMT
References: <26854@netnews.upenn.edu>
Distribution: usa
Organization: Oglevee Computer Systems, Connellsville, Pa
Lines: 46

In <26854@netnews.upenn.edu> weisen@eniac.seas.upenn.edu (Neil Weisenfeld)
writes:

>Why does the following segment of code give a conversion between
>integral types warning under MSC6.00?

>#define ACTUAL_SPACE ' '
>void strmem(char *mem, char *str, int n)
>{
>  if (str && mem)
>    while (n--)
>       *mem++=(*str)?(*str++):ACTUAL_SPACE;
>}

>The *mem++= line gets the error.  Since everything is a char, I'm not
>sure what the problem is.         ^^^^^^^^^^^^^^^^^^^^^^^^^^

Guess again.  Everything -isn't- a char.  Specifically, the character
constant ' ' has as its type -int- whose value is the code for the
corresponding character in the target character set (32 decimal in
ASCII).

I've never used MSC 6.0, but I'd assume that its warning you about 
the implicit conversion of this int value to the char value on the
left hand side of the assignment above (*mem++).  Since, by definition,
the value of a character constant expression is representable as a
char, so you can safely ignore the "warning".  On the other hand, since
ignoring compiler warning messages is a bad habit to fall into, you can
cast the character constant as a char in the assignment:

        *mem++ = ( *str ) ? *str++ : (char)ACTUAL_SPACE;

(Note:  you -could- do this cast in the #define line as:

        #define  ACTUAL_SPACE  (char)' '

but there may be places in the code where ACTUAL_SPACE is used in an
int context.)
-- 
Norm Joseph                       //   Internet: cgh!amanue!oglvee!norm@dsi.com
Oglevee Computer Systems, Inc.    //       Uucp: {pitt,cgh}!amanue!oglvee!norm
            -- "Whaddya mean he had bullet holes in his mirror?" --
-- 
Norm Joseph                       //   Internet: cgh!amanue!oglvee!norm@dsi.com
Oglevee Computer Systems, Inc.    //       Uucp: {pitt,cgh}!amanue!oglvee!norm
            -- "Whaddya mean he had bullet holes in his mirror?" --