--- Begin Message ---
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Subject: |
28.0.50; AREF: assert that the index is inside bounds |
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Date: |
Thu, 18 Jun 2020 22:12:20 +0200 |
Severity: wishlist,patch
X-Debbugs-Cc: Paul Eggert <eggert@cs.ucla.edu>, Eli Zaretskii <eliz@gnu.org>,
<uyennhi.qm@gmail.com>
I was bitten by an out-of-bounds index at AREF while working
in a new feature.
A similar assert as we do in ASET would have allowed me
to diagnostic the bug in minutes; instead, it took me
few days to realize the bug.
Is it OK for you to add the following patch?
--8<-----------------------------cut here---------------start------------->8---
commit 8d904d41fcb8ef29ac8205761077a11f900916bc
Author: Tino Calancha <tino.calancha@gmail.com>
Date: Thu Jun 18 22:01:07 2020 +0200
AREF: assert that the index is inside bounds
* src/lisp.h (gc_asize): Move before first use.
(AREF): Assert the index is inside its bounds.
* test/manual/etags/c-src/emacs/src/lisp.h (AREF):
Same.
diff --git a/src/lisp.h b/src/lisp.h
index 3442699088..21722e4a78 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -1671,6 +1671,13 @@ ASIZE (Lisp_Object array)
return size;
}
+INLINE ptrdiff_t
+gc_asize (Lisp_Object array)
+{
+ /* Like ASIZE, but also can be used in the garbage collector. */
+ return XVECTOR (array)->header.size & ~ARRAY_MARK_FLAG;
+}
+
INLINE ptrdiff_t
PVSIZE (Lisp_Object pv)
{
@@ -1853,6 +1860,7 @@ bool_vector_set (Lisp_Object a, EMACS_INT i, bool b)
INLINE Lisp_Object
AREF (Lisp_Object array, ptrdiff_t idx)
{
+ eassert (0 <= idx && idx < gc_asize (array));
return XVECTOR (array)->contents[idx];
}
@@ -1862,13 +1870,6 @@ aref_addr (Lisp_Object array, ptrdiff_t idx)
return & XVECTOR (array)->contents[idx];
}
-INLINE ptrdiff_t
-gc_asize (Lisp_Object array)
-{
- /* Like ASIZE, but also can be used in the garbage collector. */
- return XVECTOR (array)->header.size & ~ARRAY_MARK_FLAG;
-}
-
INLINE void
ASET (Lisp_Object array, ptrdiff_t idx, Lisp_Object val)
{
diff --git a/test/manual/etags/c-src/emacs/src/lisp.h
b/test/manual/etags/c-src/emacs/src/lisp.h
index eceef4c00d..b2e32554c3 100644
--- a/test/manual/etags/c-src/emacs/src/lisp.h
+++ b/test/manual/etags/c-src/emacs/src/lisp.h
@@ -1478,6 +1478,7 @@ enum
INLINE Lisp_Object
AREF (Lisp_Object array, ptrdiff_t idx)
{
+ eassert (0 <= idx && idx < gc_asize (array));
return XVECTOR (array)->contents[idx];
}
--8<-----------------------------cut here---------------end--------------->8---
In GNU Emacs 28.0.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version 3.24.5, cairo
version 1.16.0)
of 2020-06-18 built on calancha-pc.dy.bbexcite.jp
Repository revision: ba450b6f462e278fcd3bc96c88f154fce219f5fc
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux 10 (buster)
--- End Message ---
--- Begin Message ---
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Subject: |
Re: bug#41936: 28.0.50; AREF: assert that the index is inside bounds |
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Date: |
Thu, 18 Jun 2020 14:06:31 -0700 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 |
On 6/18/20 1:12 PM, Tino Calancha wrote:
> Is it OK for you to add the following patch?
Yes, good idea. I wondered a while ago (to myself) why AREF doesn't check
subscripts when Emacs is configured with --enable-checking. Now that I think
about it more, it's most likely because AREF was a macro and didn't want to
evaluate its index argument multiple times. We don't need to worry about that
any more.
aref_addr should have a similar check (off by one since one can address one past
the end of an array).
There's no need to change test/manual/etags/c-src/emacs/src/lisp.h as that's
just a data file (and changes can be harmful there as they can mess up the
tests).
I installed the attached.
0001-Check-AREF-and-aref_addr-subscripts.patch
Description: Text Data
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