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From: Neil Jerram <neil@ossau.uklinux.net>
Cc: guile-devel@gnu.org
Subject: Re: guile 1.8 and x86_64
Date: Tue, 09 May 2006 07:49:01 +0100	[thread overview]
Message-ID: <87y7xbn15u.fsf@ossau.uklinux.net> (raw)
In-Reply-To: <87k68wjib9.fsf@minimini.mvo.home> (Marius Vollmer's message of "09 May 2006 00:52:10 +0300")

Marius Vollmer <mvo@zagadka.de> writes:

> Here is what is going on: the CELL_P predicate is used during the
> conservative scanning of the GC to decide whether a random word can
> possibly be a non-immediate SCM value.  Non-immediate values are the
> ones that point into the heap.  The type tag for such a non-immediate
> value is "lower three bits zero".  On 32-bit architectures, a cell is
> 8 bytes, which means that a non-immediate value is always aligned to a
> cell.  On 64-bit machines, a cell is 16 bytes, and that means that a
> word with "lower three bits zero" can still be invalid because it
> points into the middle of a cell.
>
> (We have similar check already for double-cells, which are 16 bytes on
> 32-bit machines.)

That's great, but I believe there's one detail still to be explained:
why is it a problem with GCC 4 but not with GCC 3?

    Neil



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  reply	other threads:[~2006-05-09  6:49 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-04-07 19:40 guile 1.8 and x86_64 Quanah Gibson-Mount
2006-04-10  8:14 ` Ludovic Courtès
2006-04-10 22:55   ` Neil Jerram
2006-04-10 23:03     ` Quanah Gibson-Mount
2006-04-11 20:37       ` Neil Jerram
2006-04-11 20:52         ` Quanah Gibson-Mount
2006-05-05 14:05         ` Miroslav Lichvar
2006-05-06 11:12           ` Miroslav Lichvar
2006-05-07 21:29             ` Marius Vollmer
2006-05-08 10:28               ` Andy Wingo
2006-05-08 21:52                 ` Marius Vollmer
2006-05-09  6:49                   ` Neil Jerram [this message]
2006-05-09 13:23                     ` Andy Wingo
2006-05-09 22:31                       ` Default stack limit Marius Vollmer
2006-05-10 14:31                         ` Andy Wingo
2006-05-10 23:58                           ` Kevin Ryde

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