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

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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