From: "Davis Herring" <herring@lanl.gov>
To: "Alin Soare" <as1789@gmail.com>
Cc: Emacs Dev <emacs-devel@gnu.org>
Subject: Re: please help concerning specpdl
Date: Tue, 14 Dec 2010 16:14:50 -0800 (PST) [thread overview]
Message-ID: <60550.130.55.118.19.1292372090.squirrel@webmail.lanl.gov> (raw)
In-Reply-To: <AANLkTintAorQs8E_BnN2ULX1LPBFFjupO8eBFpWD_HZp@mail.gmail.com>
> Why let-binding-variables are memorized exactly here and not elsewhere ?
Flet memorizes their old values on the stack; when it returns (or
otherwise is exited), the old values are copied back, so they can't be
needed beyond the lifetime of that stack frame.
> why the do-while is good in this case, and not simply brackets?
So that the whole thing is one statement that needs a ;, just like a
normal function call. If it were brackets, you couldn't do
if(x) SAFE_ALLOCA(...);
else y=x;
> I see that inside unbind_to, the symbols are unbounded 1 by one. Why the
> specpdl_ptr is not decremented directly with count ?
Because you need to do something with each record: restore old values for
symbols, call functions registered with record_unwind_protect(), etc.
> Probably because unbind_to is called from lisp code by (throw 'symbol
> value), and specpdl_ptr must decrement 1 by 1 until the 'symbol is dound
> on the stack ?
catch-tags are searched separately: see struct catchtag.
> Apart from (throw ... ), is which other situation unbind_to is called ?
The other important one is Fsignal (quit and other errors).
> I see that GCPROx macros are used to protect the variables of type Lisp
> Object on the stack of C code (that the compiler creates), not to protect
> the lisp objects in specpdl. The GCPRO protection is against the algorthm
> of conservative stack. Am I right ?
I believe the GCPRO draws the attention of the stack checker to those Lisp
objects to make sure that they're not collected.
Davis
--
This product is sold by volume, not by mass. If it appears too dense or
too sparse, it is because mass-energy conversion has occurred during
shipping.
next prev parent reply other threads:[~2010-12-15 0:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-04 5:33 please help concerning specpdl Alin Soare
2010-12-06 16:22 ` Davis Herring
2010-12-14 21:25 ` Alin Soare
2010-12-15 0:14 ` Davis Herring [this message]
2010-12-15 0:53 ` Ken Raeburn
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