[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: scm_remember

From: Marius Vollmer
Subject: Re: scm_remember
Date: 04 Nov 2000 20:19:12 +0100
User-agent: Gnus/5.0803 (Gnus v5.8.3) Emacs/20.7

Dirk Herrmann <address@hidden> writes:

> > For example:
> > 
> >     SCM str;
> >     char *chars = SCM_STRING_CHARS (str);
> >     some_syscall (chars);
> >     str = SCM_BOOL_F;
> >     scm_remember (&str);
> > 
> > will ensure that the object originally pointed to by `str' is properly
> > protected, [...]
> Hmmm.  I don't think so.  Why should the original content of str be
> protected in this case?

Because I thought that the compiler will keep the location that holds
the pointer visible to the GC.  I don't know if it is required to do

> You rather protect the new content, namely #f.  In the moment when
> scm_remember (&str) is called, the str object already holds the new
> value, and this is also obvious for the compiler.  Thus, compiler
> _knows_ that &str is a pointer to the value SCM_BOOL_F.

Maybe you are right.  The current method seems to work well in
practice, nevertheless.

> Thus, the implications of scm_remember (&str) are less obvious.  Even
> worse, they are dependent of the compiler's knowledge.

Ok, I think I get it.  Thanks for explaining this so thoroughly!  I
don't feel competent in this issue, and I am pretty much convinced
that you have it right.  I still want to be conservative here.  I
don't see a immediate need to change it, because the current setup
seems to work, so we should proceed carefully.  Anyone else has an
opinion on this?  Maybe you could check with Aubrey?

reply via email to

[Prev in Thread] Current Thread [Next in Thread]