Re: [PATCH] Ghost specifiers
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Olivier Galibert <galibert(a)pobox.com> writes:
On Fri, May 01, 1998 at 12:29:42AM -0700, Ben Wing wrote:
> In the specifier code and in a lot of other code that I wrote, I had to
> copy internal lists whenever they were returned just to make sure that
> malicious code couldn't mess things up by modifying them. This is
> inefficient, and could be avoided if we had read-only lists. The same
> thing goes for strings, although they aren't generally copied.
What do you want exactly, read-only or copy-on-write ?
Read-only.
(prog1 'bar
(aset (symbol-name 'bar) 0 ?x))
=> xar
Or:
(setq bar 10)
=> 10
(aset (symbol-name 'bar) 0 ?x)
=> ?x
bar
--> Symbol's value as variable is void: bar
In both cases, `aset' should have signaled an error.
--
Hrvoje Niksic <hniksic(a)srce.hr> | Student at FER Zagreb, Croatia
--------------------------------+--------------------------------
Reporter: Mr Gandhi, what do you think of Western Civilization?
Gandhi: I think it would be a good idea.
Olivier Galibert
Friday, 1 May
Fri, 1 May
8:15 p.m.
New subject: [PATCH] Ghost specifiers
On Fri, May 01, 1998 at 08:33:01PM +0200, Hrvoje Niksic wrote:
> What do you want exactly, read-only or copy-on-write ?
Read-only.
(prog1 'bar
(aset (symbol-name 'bar) 0 ?x))
=> xar
Or:
(setq bar 10)
=> 10
(aset (symbol-name 'bar) 0 ?x)
=> ?x
bar
--> Symbol's value as variable is void: bar
In both cases, `aset' should have signaled an error.
With the indexed lrecord implementation, it is quite easy to do. But
I'm not convinced this is what you really want to have:
(setq bar 10)
10
(setq nbar (symbol-name 'bar))
"bar"
(aset nbar 0 ?x)
?x
nbar
"xar"
bar
--> Symbol's value as variable is void: bar
How am I supposed to work on the string which happens to be initially
a symbol name ? I see no "copy-string" or equivalent function.
Maybe the answer is "it is broken now, it will only detect bugs" :-)
OG.
Kirill M. Katsnelson
Friday, 1 May
Fri, 1 May
8:59 p.m.
New subject: [PATCH] Ghost specifiers
Some time ago, Olivier Galibert wrote...
|+
|
| With the indexed lrecord implementation, it is quite easy to do. But
| I'm not convinced this is what you really want to have:
|
| (setq bar 10)
| 10
| (setq nbar (symbol-name 'bar))
| "bar"
| (aset nbar 0 ?x)
| ?x
| nbar
| "xar"
| bar
| --> Symbol's value as variable is void: bar
|
| How am I supposed to work on the string which happens to be initially
| a symbol name ? I see no "copy-string" or equivalent function.
(copy-sequence) is the function you are looking for.
So, IMO the correct behavior in your sample would be that aset signals;
although if you write (setq nbar (copy-sequence (symbol-name 'bar))) it
is ok, as it mangles with a copy of the string.
Kirill
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Olivier Galibert