Re: how to generate code for (a,b):=(b,a)

Dave Lloyd <Dave@occl-cam.demon.co.uk>
22 May 1997 22:35:37 -0400

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Related articles
[12 earlier articles]
Re: how to generate code for (a,b):=(b,a) bobduff@world.std.com (1997-05-13)
Re: how to generate code for (a,b):=(b,a) will@ccs.neu.edu (William D Clinger) (1997-05-17)
Re: how to generate code for (a,b):=(b,a) wilson@cs.utexas.edu (1997-05-17)
Re: how to generate code for (a,b):=(b,a) boehm@mti.mti.sgi.com (Hans-Juergen Boehm) (1997-05-17)
Re: how to generate code for (a,b):=(b,a) boehm@mti.mti.sgi.com (Hans-Juergen Boehm) (1997-05-17)
Re: how to generate code for (a,b):=(b,a) Dave@occl-cam.demon.co.uk (Dave Lloyd) (1997-05-22)
Re: how to generate code for (a,b):=(b,a) Dave@occl-cam.demon.co.uk (Dave Lloyd) (1997-05-22)
Re: how to generate code for (a,b):=(b,a) boehm@mti.mti.sgi.com (Hans-Juergen Boehm) (1997-05-25)
Re: how to generate code for (a,b):=(b,a) Dave@occl-cam.demon.co.uk (Dave Lloyd) (1997-05-27)
Re: how to generate code for (a,b):=(b,a) fjh@murlibobo.cs.mu.OZ.AU (1997-05-30)
Re: how to generate code for (a,b):=(b,a) boehm@mti.mti.sgi.com (Hans-Juergen Boehm) (1997-05-30)
Re: how to generate code for (a,b):=(b,a) Dave@occl-cam.demon.co.uk (Dave Lloyd) (1997-06-11)
conservative GC (was Re: how to generate code for (a,b):=(b,a)) boehm@mti.mti.sgi.com (Hans-Juergen Boehm) (1997-06-13)
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From: Dave Lloyd <Dave@occl-cam.demon.co.uk>
Newsgroups: comp.compilers
Date: 22 May 1997 22:35:37 -0400
Organization: Compilers Central
References: 97-05-058 97-05-129 97-05-148
Keywords: optimize, code, GC

Paul Wilson <wilson@cs.utexas.edu> wrote:
> Hans Boehm et al. have gone to a lot of trouble to make it practical
> to garbage collect languages that weren't designed for GC. (Please
> provide a flag to turn off pointer-mangling optimizations. A
> conservative GC can handle common forms of pointer arithmetic, but if
> you split a pointer into two pieces, or xor it so that it doesn't
> point anywhere near the actual object, horrible bugs can happen. (In
> either case, if the original pointer is somewhere on the stack or in
> registers, it's okay, but if the only pointer to a live object is
> mangled beyond recognition, conservative GC's will fail.)


Best argument I've heard against conservative GC in a long time - NOT
the code-generation technique. As I mentionned in another post on this
thread, we use this technique, BUT we use a mark-and-sweep GC with our
Algol and Fortran compilers so no problem.
(I do appreciate the problem with C really <evil-grin>)


Cheers,
----------------------------------------------------------------------
Dave Lloyd mailto:Dave@occl-cam.demon.co.uk
Oxford and Cambridge Compilers Ltd http://www.occl-cam.demon.co.uk/
Cambridge, England http://www.chaos.org.uk/~dave/
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