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From: osmith@acorn.co.uk (Owen Smith)
Newsgroups: comp.sys.acorn
Subject: Re: More about BASIC vs. Pascal vs. C (the flame war continues !)
Message-ID: <5091@acorn.co.uk>
Date: 12 Feb 91 12:16:14 GMT
References: <1991Feb11.105227.15182@and.cs.liv.ac.uk>
Sender: osmith@acorn.co.uk
Distribution: comp
Organization: Acorn Computers Ltd, Cambridge, England
Lines: 57

In article <1991Feb11.105227.15182@and.cs.liv.ac.uk> rkl@and.cs.liv.ac.uk
writes:

>I was dabbling in C on our HP UNIX boxes a while back and I was shocked at
>the complete lack of warning about the following:
>
>hello(param1,param2)
>int param1,param2;
>{
>   printf("Param 2 = %d\n",param2);
>}
>
>main()
>{
>   hello(1);
>}

Your compiler did the "correct" thing. The definition of the function hello()
merely acts as a declaration of

hello();

since you have used a traditional C definition. Thus when you make the
hello(1) call, everything looks fine to the compiler. It has no idea how
many parameters hello() has or what type they should be. The fact that the
function definition is in the same file makes no difference whatsoever. Indeed
I would be worried if your compiler did give a warning as that would imply
it was non-standard and may well cause porting problems.

If you had instead written

void hello
(
    int         param1,
    int         param2
)
{
    printf("Param 2 = %d\n", param2);
}

then in this case you would have got a warning, since an ANSI style function
definition also acts as a declaration of the function with the appropriate
function prototype:

void hello
(
    int         param1,
    int         param2
);

You must remember the difference between a DEFINITION and a DECLARATION when
you are programming in C. One of the things that BASIC lacks altogether is
declarations.

Owen (a C programmer, lost in the wilderness)

The views expressed are my own and are not necessarily those of Acorn.