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Path: utzoo!utcsri!greg
From: greg@utcsri.UUCP (Gregory Smith)
Newsgroups: net.lang.c
Subject: Re: icky C code
Message-ID: <3221@utcsri.UUCP>
Date: Sun, 3-Aug-86 23:28:28 EDT
Article-I.D.: utcsri.3221
Posted: Sun Aug  3 23:28:28 1986
Date-Received: Wed, 6-Aug-86 10:24:06 EDT
References: <2239@brl-smoke.ARPA>
Reply-To: greg@utcsri.UUCP (Gregory Smith)
Organization: CSRI, University of Toronto
Lines: 34
Summary: 

In article <19880@rochester.ARPA> crowl@rochtest.UUCP (Lawrence Crowl) writes:
>In article <3117@utcsri.UUCP>, greg@utcsri.UUCP (Gregory Smith) writes:
>> From a code efficiency
>> standpoint, for example, a 68000 should return int's in D0 and all pointer
>> types in A0, which would break the above. ( Somebody pointed out that a
>> certain 68K compiler has an option to return both types in *both* regs ).
>
>Since there is no type checking between an external definition of a function

	There is lint, which does this.

>and its actual definition, a programmer could implicitly type cast by listing
>the external definition with a different return type than the actual.  If
>integers are put in D0 and addresses in A0, then the calling function would
>grab the return value from the wrong register.
>
>So, the optimization would probably break some programs.

Very likely, but only incorrect ones. This 'implicit casting' is not
legal C. It is much the same as passing an int to a function which
expects a struct containing a single int - it will usually work, but if
(when) it doesn't, the programmer is at fault. Would you call that
'implicit casting'?

 I assert that a 68K C implementation could be made which returns
pointers in A0 and ints in D0, and no lintable program would be broken.
(If this is not the case, then lint needs work :-) )


-- 
"You'll need more than a Tylenol if you don't tell me where my father is!"
						- The Ice Pirates
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Greg Smith     University of Toronto      UUCP: ..utzoo!utcsri!greg