Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!usc!apple!apple.com!chewy
From: chewy@apple.com (Paul Snively)
Newsgroups: comp.sys.mac.programmer
Subject: Re: compiler-generated code quality (Re: Pascal deficiency?)
Message-ID: <11604@goofy.Apple.COM>
Date: 20 Dec 90 19:40:57 GMT
References: <9611@ncar.ucar.edu>
Sender: usenet@Apple.COM
Organization: Apple Computer, Inc.
Lines: 32

In article <9611@ncar.ucar.edu> hpoppe@ncar.ucar.edu (Herb Poppe) writes:
> > Note that a real compiler will generate _no_ code for the above 
> procedures
> > (other than procedure entry/exit stuff), because the value isn't used
> > anywhere. Similarly, if you try to fix that by saying
> >         a () { int x; x = 1; x = x + 1; xyzzy(x); }
> > 
> > gcc (which, for the purposes of this discussion, certainly counts as a 
> real
> > compiler) will push the value 2 onto the stack without bothering to 
> create
> > and increment a variable.
> 
> If that is the case, if I were to "debug" this routine with a symbolic 
> debugger, what would it show as the value of "x"?

From "Using and Porting GNU CC," page 14, I quote:

"Unlike most other C compilers, GNU CC allows you to use '-g' with '-O'.  
The shortcuts taken by optimized code may occassionally produce surprising 
results: some variables you declared may not exist at all..."

__________________________________________________________________________
                                Paul Snively
                      Macintosh Developer Technical Support
                             Apple Computer, Inc.

chewy@apple.com

Just because I work for Apple Computer, Inc. doesn't mean that I believe 
what they believe, or vice-versa.
__________________________________________________________________________