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From: ark@alice.UUCP
Newsgroups: comp.lang.c
Subject: Re: IBM RT compiler weirdness
Message-ID: <7247@alice.UUCP>
Date: Sat, 29-Aug-87 10:50:15 EDT
Article-I.D.: alice.7247
Posted: Sat Aug 29 10:50:15 1987
Date-Received: Wed, 2-Sep-87 02:08:51 EDT
References: <261@calyx.UUCP>
Organization: AT&T Bell Laboratories, Liberty Corner NJ
Lines: 36

In article <261@calyx.UUCP>, usenet@calyx.UUCP writes:
> Keywords:missing semicolons, lint, silent!
> #include <stdio.h>
> 
> struct junk {
> 	int a;
> 	int b;
> }
> 
> main(argc,argv)
> int argc;
> char **argv;
> {
	[ program body deleted ]

> It compiled fine.  Lint said nothing.  But the output was garbage: it seems
> that the missing semi-colon after the struct definition caused argc
> to be given the value of argv, and argv got the value of the environment
> varible pointer.

No, the missing semi-colon after the struct definition said
that your program returns a "struct junk".

From your description, it appears that your compiler handles
structure returns by passing an extra argument to the function
in question, presumably to hold the address of memory in which to
place the returned structure.  This is a legitimate way of doing
it -- and in fact has some advantages over the way most C
compilers seem to work -- but does have the disadvantage that
some invalid programs which work by coincidence on most implementations
will blow up on this one.

In particular, a function which returns a different type from
the type declared for it will result in just about the kind of
problem you've described.  Since main() is supposed to return
an int, and you've made it return a struct, you're out of luck.