From 4612d1eab721a1010312382d1048c8b3a67b18fa Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Sun, 7 Sep 2014 15:27:59 -0700
Subject: [PATCH] Fix bug uncovered by changing alloca to auto buffer.
* coding.c (growable_destination): New function.
(produce_chars): Use it for sanity checks. Do not fiddle with
dst_end if the source and destination are both nil, as it's
the caller's responsibility to avoid overlap.
* keyboard.c (read_decoded_event_from_main_queue):
The destination must be MAX_MULTIBYTE_LENGTH times the max source
length, not 4 times, to prevent decode_coding_c_string from trying
to reallocate a destination. This removes the need for the FIXME.
Fixes: debbugs:18410
---
src/ChangeLog | 10 ++++++++++
src/coding.c | 20 ++++++++++++++++++--
src/keyboard.c | 13 +++----------
3 files changed, 31 insertions(+), 12 deletions(-)
diff --git a/src/ChangeLog b/src/ChangeLog
index 88ab1eedca8..2654abd32d4 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,15 @@
2014-09-07 Paul Eggert <eggert@cs.ucla.edu>
+ Fix bug uncovered by changing alloca to auto buffer (Bug#18410).
+ * coding.c (growable_destination): New function.
+ (produce_chars): Use it for sanity checks. Do not fiddle with
+ dst_end if the source and destination are both nil, as it's
+ the caller's responsibility to avoid overlap.
+ * keyboard.c (read_decoded_event_from_main_queue):
+ The destination must be MAX_MULTIBYTE_LENGTH times the max source
+ length, not 4 times, to prevent decode_coding_c_string from trying
+ to reallocate a destination. This removes the need for the FIXME.
+
* callproc.c (exec_failed) [DOS_NT]: Define a dummy.
All callers simplified. Add a comment about exec_failed, vfork,
and alloca.
diff --git a/src/coding.c b/src/coding.c
index 84b774b4355..ed107a297ba 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -690,6 +690,14 @@ CHECK_NATNUM_CDR (Lisp_Object x)
XSETCDR (x, tmp);
}
+/* True if CODING's destination can be grown. */
+
+static bool
+growable_destination (struct coding_system *coding)
+{
+ return STRINGP (coding->dst_object) || BUFFERP (coding->dst_object);
+}
+
/* Safely get one byte from the source text pointed by SRC which ends
at SRC_END, and set C to that byte. If there are not enough bytes
@@ -7019,8 +7027,10 @@ produce_chars (struct coding_system *coding, Lisp_Object translation_table,
int *buf = coding->charbuf;
int *buf_end = buf + coding->charbuf_used;
- if (EQ (coding->src_object, coding->dst_object))
+ if (EQ (coding->src_object, coding->dst_object)
+ && ! NILP (coding->dst_object))
{
+ eassert (growable_destination (coding));
coding_set_source (coding);
dst_end = ((unsigned char *) coding->source) + coding->consumed;
}
@@ -7059,6 +7069,7 @@ produce_chars (struct coding_system *coding, Lisp_Object translation_table,
if ((dst_end - dst) / MAX_MULTIBYTE_LENGTH < to_nchars)
{
+ eassert (growable_destination (coding));
if (((min (PTRDIFF_MAX, SIZE_MAX) - (buf_end - buf))
/ MAX_MULTIBYTE_LENGTH)
< to_nchars)
@@ -7103,7 +7114,10 @@ produce_chars (struct coding_system *coding, Lisp_Object translation_table,
const unsigned char *src_end = src + coding->consumed;
if (EQ (coding->dst_object, coding->src_object))
- dst_end = (unsigned char *) src;
+ {
+ eassert (growable_destination (coding));
+ dst_end = (unsigned char *) src;
+ }
if (coding->src_multibyte != coding->dst_multibyte)
{
if (coding->src_multibyte)
@@ -7119,6 +7133,7 @@ produce_chars (struct coding_system *coding, Lisp_Object translation_table,
ONE_MORE_BYTE (c);
if (dst == dst_end)
{
+ eassert (growable_destination (coding));
if (EQ (coding->src_object, coding->dst_object))
dst_end = (unsigned char *) src;
if (dst == dst_end)
@@ -7149,6 +7164,7 @@ produce_chars (struct coding_system *coding, Lisp_Object translation_table,
if (dst >= dst_end - 1)
{
+ eassert (growable_destination (coding));
if (EQ (coding->src_object, coding->dst_object))
dst_end = (unsigned char *) src;
if (dst >= dst_end - 1)
diff --git a/src/keyboard.c b/src/keyboard.c
index eef0770684e..c435ba74faa 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -2355,22 +2355,15 @@ read_decoded_event_from_main_queue (struct timespec *end_time,
struct coding_system *coding
= TERMINAL_KEYBOARD_CODING (terminal);
unsigned char src[MAX_ENCODED_BYTES];
- unsigned char dest[4 * sizeof src];
+ unsigned char dest[MAX_ENCODED_BYTES * MAX_MULTIBYTE_LENGTH];
int i;
for (i = 0; i < n; i++)
src[i] = XINT (events[i]);
if (meta_key != 2)
for (i = 0; i < n; i++)
src[i] &= ~0x80;
-
- /* FIXME: For some reason decode_coding_c_string requires a
- fresh output buffer each time, and reusing the old buffer can
- make Emacs dump core. Avoid triggering the problem for now
- by allocating a new buffer each time through the loop. */
- bool please_fixme = true;
- coding->destination = please_fixme ? alloca (n * 4) : dest;
-
- coding->dst_bytes = n * 4;
+ coding->destination = dest;
+ coding->dst_bytes = sizeof dest;
decode_coding_c_string (coding, src, n, Qnil);
eassert (coding->produced_char <= n);
if (coding->produced_char == 0)
--
2.39.5