* I don't understand this comment on message2
@ 2005-09-19 8:30 Kim F. Storm
2005-09-20 19:43 ` Richard M. Stallman
0 siblings, 1 reply; 3+ messages in thread
From: Kim F. Storm @ 2005-09-19 8:30 UTC (permalink / raw)
I have studied the code in message2 and the functions called by it
quite a lot (hunting for GC-related errors), and I don't understand
the restrictions in the second paragraph of message2's commentary
(included below).
It is indeed not safe to pass data from a lisp string (due to
potential GC), but not for the reasons listed. I cannot find any
place where the buffer M is stored for later reference.
So using alloca'ed memory seems safe to me.
Can anyone enlighten me?
/* Display an echo area message M with a specified length of NBYTES
bytes. The string may include null characters. If M is 0, clear
out any existing message, and let the mini-buffer text show
through.
The buffer M must continue to exist until after the echo area gets
cleared or some other message gets displayed there. This means do
not pass text that is stored in a Lisp string; do not pass text in
a buffer that was alloca'd. */
void
message2 (m, nbytes, multibyte)
--
Kim F. Storm <storm@cua.dk> http://www.cua.dk
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: I don't understand this comment on message2
2005-09-19 8:30 I don't understand this comment on message2 Kim F. Storm
@ 2005-09-20 19:43 ` Richard M. Stallman
2005-09-22 13:58 ` Kim F. Storm
0 siblings, 1 reply; 3+ messages in thread
From: Richard M. Stallman @ 2005-09-20 19:43 UTC (permalink / raw)
Cc: emacs-devel
The buffer M must continue to exist until after the echo area gets
cleared or some other message gets displayed there. This means do
not pass text that is stored in a Lisp string; do not pass text in
a buffer that was alloca'd. */
I think that comment is probably obsolete. Nowadays the echo area
text is stored in real buffers. Before Emacs 20, I think it was
stored in null-terminated C strings.
You could double-check this by looking at the code from Emacs 19.
If this comment was needed for that reason, it can be deleted now.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: I don't understand this comment on message2
2005-09-20 19:43 ` Richard M. Stallman
@ 2005-09-22 13:58 ` Kim F. Storm
0 siblings, 0 replies; 3+ messages in thread
From: Kim F. Storm @ 2005-09-22 13:58 UTC (permalink / raw)
Cc: emacs-devel
"Richard M. Stallman" <rms@gnu.org> writes:
> The buffer M must continue to exist until after the echo area gets
> cleared or some other message gets displayed there. This means do
> not pass text that is stored in a Lisp string; do not pass text in
> a buffer that was alloca'd. */
>
> I think that comment is probably obsolete. Nowadays the echo area
> text is stored in real buffers. Before Emacs 20, I think it was
> stored in null-terminated C strings.
>
> You could double-check this by looking at the code from Emacs 19.
> If this comment was needed for that reason, it can be deleted now.
That was the reason, yes. I have rewritten the comment.
--
Kim F. Storm <storm@cua.dk> http://www.cua.dk
^ permalink raw reply [flat|nested] 3+ messages in thread
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2005-09-19 8:30 I don't understand this comment on message2 Kim F. Storm
2005-09-20 19:43 ` Richard M. Stallman
2005-09-22 13:58 ` Kim F. Storm
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