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bug#8318: int overflow problem in SAFE_ALLOCA, SAFE_ALLOCA_LISP
From: |
Paul Eggert |
Subject: |
bug#8318: int overflow problem in SAFE_ALLOCA, SAFE_ALLOCA_LISP |
Date: |
Tue, 22 Mar 2011 02:12:52 -0700 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.14) Gecko/20110223 Thunderbird/3.1.8 |
The SAFE_ALLOCA macro assumes that adding 1 to the integer
variable sa_must_free cannot overflow, but this assumption
is incorrect in some cases. I plan to commit the following
patch to fix this.
I found this bug using gcc 4.5.2 -O2 -Wstrict-overflow.
* lisp.h (SAFE_ALLOCA, SAFE_ALLOCA_LISP): Avoid 'int' overflow
leading to a memory leak, possible in functions like
load_charset_map_from_file that can allocate an unbounded number
of objects.
=== modified file 'src/lisp.h'
--- src/lisp.h 2011-03-18 04:58:44 +0000
+++ src/lisp.h 2011-03-22 09:04:53 +0000
@@ -3602,7 +3602,7 @@
else \
{ \
buf = (type) xmalloc (size); \
- sa_must_free++; \
+ sa_must_free = 1; \
record_unwind_protect (safe_alloca_unwind, \
make_save_value (buf, 0)); \
} \
@@ -3632,7 +3632,7 @@
buf = (Lisp_Object *) xmalloc (size_); \
arg_ = make_save_value (buf, nelt); \
XSAVE_VALUE (arg_)->dogc = 1; \
- sa_must_free++; \
+ sa_must_free = 1; \
record_unwind_protect (safe_alloca_unwind, arg_); \
} \
} while (0)
- bug#8318: int overflow problem in SAFE_ALLOCA, SAFE_ALLOCA_LISP,
Paul Eggert <=