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bug#17298: 24.4.50; emacs_backtrace
From: |
Stefan Monnier |
Subject: |
bug#17298: 24.4.50; emacs_backtrace |
Date: |
Sat, 19 Apr 2014 13:55:39 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux) |
> I really wish someone who knows those parts of Emacs would look into
> this problem.
I don't know those parts very well, but it seems that the patch below
might make sense.
I have a hard time believing that we've lived with such a bug for so
many years, but this makes the code agree with the comment, and if you
look at the diagram before the function, I think the comment is right
and the code is wrong.
Just to clarify the crucial part of the patch is:
- interval->total_length -= B->total_length - LEFT_TOTAL_LENGTH (interval);
+ interval->total_length -= B->total_length - TOTAL_LENGTH (c);
-- Stefan
=== modified file 'src/intervals.c'
--- src/intervals.c 2014-01-21 02:28:57 +0000
+++ src/intervals.c 2014-04-19 17:51:01 +0000
@@ -334,10 +334,16 @@
static INTERVAL
rotate_right (INTERVAL interval)
{
- INTERVAL i;
+ INTERVAL c;
INTERVAL B = interval->left;
ptrdiff_t old_total = interval->total_length;
+ eassert (TOTAL_LENGTH (interval) > 0);
+ eassert (TOTAL_LENGTH (interval)
+ > TOTAL_LENGTH (B) + TOTAL_LENGTH (interval->right));
+ eassert (TOTAL_LENGTH (B)
+ > TOTAL_LENGTH (B->left) + TOTAL_LENGTH (B->right));
+
/* Deal with any Parent of A; make it point to B. */
if (! ROOT_INTERVAL_P (interval))
{
@@ -348,23 +354,23 @@
}
copy_interval_parent (B, interval);
- /* Make B the parent of A */
- i = B->right;
+ /* Make B the parent of A. */
+ c = B->right;
set_interval_right (B, interval);
set_interval_parent (interval, B);
- /* Make A point to c */
- set_interval_left (interval, i);
- if (i)
- set_interval_parent (i, interval);
+ /* Make A point to c. */
+ set_interval_left (interval, c);
+ if (c)
+ set_interval_parent (c, interval);
/* A's total length is decreased by the length of B and its left child. */
- interval->total_length -= B->total_length - LEFT_TOTAL_LENGTH (interval);
- eassert (TOTAL_LENGTH (interval) >= 0);
+ interval->total_length -= B->total_length - TOTAL_LENGTH (c);
+ eassert (TOTAL_LENGTH (interval) > 0);
/* B must have the same total length of A. */
B->total_length = old_total;
- eassert (TOTAL_LENGTH (B) >= 0);
+ eassert (TOTAL_LENGTH (B) > 0);
return B;
}
@@ -381,7 +387,7 @@
static INTERVAL
rotate_left (INTERVAL interval)
{
- INTERVAL i;
+ INTERVAL c;
INTERVAL B = interval->right;
ptrdiff_t old_total = interval->total_length;
@@ -395,23 +401,23 @@
}
copy_interval_parent (B, interval);
- /* Make B the parent of A */
- i = B->left;
+ /* Make B the parent of A. */
+ c = B->left;
set_interval_left (B, interval);
set_interval_parent (interval, B);
- /* Make A point to c */
- set_interval_right (interval, i);
- if (i)
- set_interval_parent (i, interval);
+ /* Make A point to c. */
+ set_interval_right (interval, c);
+ if (c)
+ set_interval_parent (c, interval);
/* A's total length is decreased by the length of B and its right child. */
- interval->total_length -= B->total_length - RIGHT_TOTAL_LENGTH (interval);
- eassert (TOTAL_LENGTH (interval) >= 0);
+ interval->total_length -= B->total_length - TOTAL_LENGTH (c);
+ eassert (TOTAL_LENGTH (interval) > 0);
/* B must have the same total length of A. */
B->total_length = old_total;
- eassert (TOTAL_LENGTH (B) >= 0);
+ eassert (TOTAL_LENGTH (B) > 0);
return B;
}