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From: thomps@gitpyr.UUCP (Ken Thompson)
Newsgroups: net.lang.c
Subject: Re: need help with a delcaration
Message-ID: <2233@gitpyr.UUCP>
Date: Tue, 9-Sep-86 09:41:38 EDT
Article-I.D.: gitpyr.2233
Posted: Tue Sep  9 09:41:38 1986
Date-Received: Tue, 9-Sep-86 23:56:32 EDT
References: <3594@brl-smoke.ARPA> <1219@drutx.UUCP>
Organization: Georgia Institute of Technology
Lines: 35
Summary: int is correct I think



In article <1219@drutx.UUCP>, qwerty@drutx.UUCP (Brian Jones) writes:
> In the sequence:
> 
> 	main()
> 	{
> 		char c = 'w';
> 		foo(c)
> 	}
> 
> 	foo(ch)
> 	char ch;
> 
> char ch is the correct declaration.  The compiler/code generator should
> handle pulling the character portion of the promoted variable off the
> stack correctly.  Declaring it 'int' is asking for trouble.
> 
  If I understand what Kernighan and Ritchie say in their book, then ch
  is automatically converted to an int when foo is called because a function
  argument is an expression and a character is always converted to an int in
  an expression. See K&R page 41 - 42.
  I know that some compilers take care of this and allow you to
  still declare ch as a char. However, I note that K&R always declare 
  ch as an int in their examples. I would suppose that the compiler being
  used requires the int declaration. Since the conversion occurs by definition
  of the language, there is no danger in declaring it an int and this is
  commonly done in most C code. Declare it as an int and go to it. It also
  sounds like the asker of the original question should get hold of K&R and
  learn about the relationship between char and int in C.
-- 
Ken Thompson
Georgia Tech Research Institute
Georgia Insitute of Technology, Atlanta Georgia, 30332
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