Path: utzoo!attcan!uunet!mcsun!hp4nl!fwi.uva.nl!beemster
From: beemster@fwi.uva.nl (Marcel Beemster)
Newsgroups: comp.arch
Subject: Re: RISC hard to program?
Message-ID: <1139@carol.fwi.uva.nl>
Date: 13 Jul 90 08:03:27 GMT
References: <40088@mips.mips.COM> <2162@opus.cs.mcgill.ca>
Sender: news@fwi.uva.nl
Lines: 64

peterd@opus.cs.mcgill.ca (Peter Deutsch) writes:
>unportable software, etc I would allege that that the SPARC
>architecture appears to be inherently less forgiving of the
>programmer than the 68k architecture. I keep receiving
>reports of software that ran fine on machine 'x' (often
>68k machines, Vaxen etc) but that either wont compile or
>wont run on the Sun 4's. I have had this explained to me

>Now to the question: First, is it true that SPARC is
>inherently less forgiving?

No, not always. The following program reflects a bug that actually
occurred on software developed on a Sun-4. Things ran fine until the
software was ported to a Sun-3:

---------------
main()
{
  pr3( "Hello" , "world" , "!\n" ) ;
  pr3( "This" , "is wrong" ) ;
}

pr3( s1 , s2 , s3 )
char *s1, *s2, *s3 ;
{
  printf( "%s %s %s" , s1 , s2 , s3 ) ;
}
--------------End of program

As you see, the second call to pr3() lacks one parameter. When run
on a Sun-4, compiled with either -O or not, the output is:

hello world !
This is wrong !

When run on a Sun-3, the output is:

hello world !
This is wrong (null)

Now you might argue that the Sun-3's answer is more correct than the
Sun-4's, but in the abovementioned software the first call had left the
correct parameter on the register stack for a subsequent call. Of course
all this has more to do with parameter-passing conventions than
RISC vs. CISC.

Now this is just one counterexample. In general my feelings towards
software development are: "If it runs on s SPARC, it runs everywhere",
i.e., if you want to send reliable software out to the world, develop on
a machine with a highly optimizing compiler, not one of those
C-is-just-a-macro-assembler-kind-of-thing.

>So, here's the clincher. My collegue claims there are NO C
>programs that will:
>a) Pass lint on the Sun 3
>b) Pass lint on the Sun 4
>c) Run, giving a "correct" answer on the Sun3, without crashing.
>d) Either crash or give the "wrong" answer on the Sun 4.

pr3: variable # of args.        ts.c(9)  ::  ts.c(4)
printf returns value which is always ignored

++marcel				beemster@fwi.uva.nl
"So they destroyed their planet, why?", "That was better for the economy..."