Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!ll-xn!mit-eddie!bloom-beacon!athena.mit.edu!peter
From: peter@athena.mit.edu (Peter J Desnoyers)
Newsgroups: comp.arch
Subject: Re: Bad RISC
Message-ID: <3406@bloom-beacon.MIT.EDU>
Date: 2 Mar 88 17:55:24 GMT
References: <216@wsccs.UUCP>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: peter@athena.mit.edu (Peter J Desnoyers)
Organization: Massachusetts Institute of Technology
Lines: 33
Keywords: SUN RISC
Summary: sign extension a bug???

The main complaints we seem to have heard about the C compiler for the
SUN 4 are:

   1) it sign-extends characters passed as arguments. This is, I
believe, required by K&R, so it better do so. The problem that bites
everyone is whether the type being used is 'unsigned char' or signed
'char' - you don't always have a choice. Any code that relies on the
existence of unsigned/signed chars or longs, especially when it is
careless about specifying their signedness, is a definite lose on a
lot of machines. (I assume it would be a lose on many RISC's, as it
loses on an awful lot of CISC, byte-addressing machines.)

   2) it doesn't handle return values where the type is 'resolved' by
the linker. I have never worked with a C compiler, to my knowledge,
which runs any passes after the linker to incorporate these 'resolved'
types :-). I can see two problems here - (1) the compiler is paranoid
and wants type information to ensure that the value is aligned. Then
the compiler is not source-code compatible with the Sun 3 one, even
though it's the fault of Sun and not their Sparc chip. (2) you are
returning a non-aligned value at runtime - then your code is WRONG,
and shouldn't have worked on the Sun 3, either.

I think the problem here may be some people (like you said, your boss
had more problems than you did) who have spent most of their time
working on one machine, and have never seen how to fix a portability
problem like characters getting sign-extended. It is compounded by the
fact that Sun probably did not make their compiler source-code
compatible, when except for unportable code, they could have. (At the
cost of more run-time crashes while debugging) Take heart, though - at
least you got newer and faster machines in return for all this B.S.
Some people have had to go through this just for a new operating
system release.

				Peter Desnoyers