lclint-interest message 85

To: Richard A OKeefe 
Cc: lclint-interest@larch.lcs.mit.edu, lclint@larch.lcs.mit.edu,
        buechler@ateng.az.honeywell.com
Subject: Re: Formal array size check request 
In-Reply-To: Your message of "Fri, 05 Jul 1996 12:19:13 +1000."
             <199607050219.MAA28510@yallara.cs.rmit.EDU.AU> 
Date: Fri, 05 Jul 1996 10:04:33 -0700
From: Pete Buechler 

Richard -

>    It is a bad idea to put formal parameter names in prototypes.
>    To an audience concerned with writing correct code, I don't need
>    to explain why.


Well, I like to think that I am concerned with writing correct code, but I
still need to have this explained.

I know that the formal parameters are ignored in the function prototype, but I
thought that they were a good idea from the point of view of making the code
understandable. For instance, for which of the following prototypes will a coder
most likely get the parameter order correct?

char *strtok(char *, char *)

OR

char *strtok(char *token_string, char *separator_string)

If then the function is defined as

char *strtok char *s1, char *s2)

what harm has been done?

I suppose there would be a problem if somebody changed the order of the
parameters in the definition without changing them in the prototype. There
would be no check which would find this change. On the other hand, if there are
no names, there is still no check to find the change, and coders who mistakenly
used the old parameter ordering are still in big trouble when they link to the
function using the new ordering.

> Many students are putting prototypes inside functions.
> I don't suppose I need to explain the dangers of this either.

Um, yes, please do. Am I correct in believing that the problem is that the
student expects the extern declaration to be visible only within the block
in which is is defined, while in fact is is visible for the rest of the
translation unit?

Our rule here is that prototypes for globally visible functions must be placed
in header files. Then this header file must be included by any code which uses
the function, and especially by the code which defines the function. Otherwise
there is no check that the definition is compatible with the prototype. Is this
what you require of your students?

-Pete-