From: Leo <sdl.web@gmail.com>
To: emacs-devel@gnu.org
Subject: How and when to use GCPRO?
Date: Mon, 27 Dec 2010 09:21:54 +0000 [thread overview]
Message-ID: <m1oc87in9p.fsf@cam.ac.uk> (raw)
Hello,
I wonder if anyone can point me to a more detailed explanation of how
and when to use GCPRO other than what's in the elisp manual.
Is there any symptom in a gdb session that one should suspect a GCPRO is
missing?
For example, Could someone comment on the following function I just
wrote, which tries to add support for feature expressions like in common
lisp?
static Lisp_Object
eval_feature_expression (form)
Lisp_Object form;
{
Lisp_Object val, exp;
struct gcpro gcpro1;
if (! NILP(Fatom(form)))
return NILP(Fmemq(form, Vfeatures)) ? Qnil:Qt;
if (EQ (Fcar(form), Qnot))
{
if (XINT(Flength(form)) != 2)
error ("Invalid feature expression");
val = eval_feature_expression (Fcar(Fcdr(form)));
return NILP(val) ? Qt:Qnil;
}
if (EQ (Fcar(form), Qand))
{
if (NILP (Fcdr (form)))
error ("Invalid feature expression");
val = eval_feature_expression (Fcar (Fcdr (form)));
if (NILP (Fcdr (Fcdr (form))))
return val;
else if (NILP(val))
return Qnil;
else
{
GCPRO1(exp);
exp = Fcons (Qand, (Fcdr(Fcdr(form))));
val = eval_feature_expression (exp);
UNGCPRO;
return val;
}
}
if (EQ (Fcar(form), Qor))
{
if (NILP (Fcdr (form)))
error ("Invalid feature expression");
val = eval_feature_expression (Fcar (Fcdr (form)));
if (NILP (Fcdr (Fcdr (form))))
return val;
else if (NILP (val))
{
GCPRO1(exp);
exp = Fcons (Qor, (Fcdr(Fcdr(form))));
UNGCPRO;
return eval_feature_expression (exp);
}
else
return Qt;
}
error ("Invalid feature expression");
}
I am also reading the XEmacs internals manual on GCPROing but I have
little idea what is still true for GNU Emacs.
Thanks in advance and happy holidays.
Leo
next reply other threads:[~2010-12-27 9:21 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-27 9:21 Leo [this message]
2010-12-27 10:15 ` How and when to use GCPRO? Andreas Schwab
2010-12-27 10:38 ` Leo
2010-12-27 11:17 ` Andreas Schwab
2010-12-27 16:00 ` Stefan Monnier
2010-12-27 17:51 ` Andreas Schwab
2010-12-28 1:01 ` Stefan Monnier
2010-12-28 1:33 ` Daniel Colascione
2010-12-28 2:17 ` Stefan Monnier
2010-12-28 3:37 ` Daniel Colascione
2010-12-28 4:15 ` Stefan Monnier
2010-12-28 4:36 ` Conservative scanning (was: Re: How and when to use GCPRO?) Daniel Colascione
2010-12-28 17:07 ` How and when to use GCPRO? Richard Stallman
2010-12-27 19:15 ` Leo
2010-12-27 19:26 ` Common Lisp like feature expressions (was: How and when to use GCPRO?) Leo
2010-12-27 19:38 ` Andreas Schwab
2010-12-27 19:57 ` Leo
2010-12-28 1:01 ` Common Lisp like feature expressions Stefan Monnier
2010-12-28 15:26 ` Leo
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