Re: Crash during access_keymap

[Kim F. Storm]

YAMAMOTO Mitsuharu <address@hidden> writes:

>>>>>> On Sun, 13 Nov 2005 23:54:29 -0500, "Richard M. Stallman" 
>>>>>> <address@hidden> said:
>
>>> So, if there's a non-pure object that is only pointed to by pure
>>> objects, which may happen if the assumption for the pure storage is
>>> violated, then the object is reachable but get collected.
>
>> Is there evidence that this is in fact happening?
>
> David (and others) are distributing precompiled GNU Emacs binaries
> with additional files preloaded.  And they see a problem (so-called
> "commandp" one) which I don't see with the CVS version.  I suspect
> this is due to the situation above, but there's no evidence yet.
>
>> If so, can you see a general rule for how to prevent it from
>> happening?
>
> I think compile-time analysis would not become perfect because of
> dynamic bindings.
>
> On some systems including Mac OS X, the pure storage is not remapped
> to the text segment.  But still one can set watchpoint to the array
> `pure' to do run-time check.  I think it is sufficient if additional
> preloading is for developers/power-users rather than for ordinary
> users.

It seems to be possible to have a check_pure_storage function which
would traverse pure storage and validate that it only refers to
other pure object -- and also that pure storage only contains
valid objects (e.g. I don't think storing a buffer or window object
in pure storage makes any sense).

This function only needed to be run once during the build process,
e.g. just before undump.

-- 
Kim F. Storm <address@hidden> http://www.cua.dk