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Unbalanced change hooks (part 1)
From: |
Alan Mackenzie |
Subject: |
Unbalanced change hooks (part 1) |
Date: |
Sun, 31 Jul 2016 10:16:17 +0000 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
Hello, Emacs.
In certain buffer modifications, after-change-hooks is being called, yet
before-change-hooks is not being called. This is a Bad Thing, and is at
the root of bug #24074/#24094. The documentation (page "Change Hooks"
in the Elisp manual) is quite clear, if a little implicit, that both
hooks, or neither (when inhibit_modification_hooks is non-nil) get
called on a buffer modification.
The first of these problems is in Finsert_file_contents, where
before-change-hooks is invoked by a call to prepare_to_modify_buffer
(which calls signal_before_change), and after-change-hooks is invoked by
a call to signal_after_change.
Both of these invocations are conditional (which is correct), but
different conditions are applied to the before-... and after-...
invocations (which is not correct). The after-... condition tests both
parameters `visit' and `replace', but the before-... condition tests
only `visit'. It seems likely that the test on `replace' was added at a
later date, and it was mistakenly missed out of the before-...
condition.
I propose to amend Finsert_file_contents so that the same condition is
tested for the invocation of both hooks, and to enforce this by
recording the state in a bool variable. Comments on this proposed
change are requested:
diff --git a/src/fileio.c b/src/fileio.c
index b1f9d3c..0431cbc 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -3440,6 +3440,7 @@ by calling `format-decode', which see. */)
/* SAME_AT_END_CHARPOS counts characters, because
restore_window_points needs the old character count. */
ptrdiff_t same_at_end_charpos = ZV;
+ bool run_change_hooks;
if (current_buffer->base_buffer && ! NILP (visit))
error ("Cannot do file visiting in an indirect buffer");
@@ -4077,7 +4078,9 @@ by calling `format-decode', which see. */)
/* For a special file, all we can do is guess. */
total = READ_BUF_SIZE;
- if (NILP (visit) && total > 0)
+ run_change_hooks = ((NILP (visit) || !NILP (replace))
+ && total > 0);
+ if (run_change_hooks)
{
if (!NILP (BVAR (current_buffer, file_truename))
/* Make binding buffer-file-name to nil effective. */
@@ -4313,8 +4316,7 @@ by calling `format-decode', which see. */)
/* Call after-change hooks for the inserted text, aside from the case
of normal visiting (not with REPLACE), which is done in a new buffer
"before" the buffer is changed. */
- if (inserted > 0 && total > 0
- && (NILP (visit) || !NILP (replace)))
+ if (run_change_hooks)
{
signal_after_change (PT, 0, inserted);
update_compositions (PT, PT, CHECK_BORDER);
Unfortunately, this amendment, by itself, doesn't fix #240[79]4, since
there are other causes for the change hooks being improperly invoked.
--
Alan Mackenzie (Nuremberg, Germany).
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