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[Bug-gnulib] portability fix for calloc size_t overflow bug
From: |
Paul Eggert |
Subject: |
[Bug-gnulib] portability fix for calloc size_t overflow bug |
Date: |
Wed, 17 Nov 2004 15:06:39 -0800 |
User-agent: |
Gnus/5.1006 (Gnus v5.10.6) Emacs/21.3 (gnu/linux) |
While we're on the subject of working around buggy allocators, I
installed this:
2004-11-17 Paul Eggert <address@hidden>
* lib/calloc.c (rpl_calloc): Defend against buggy calloc implementations
that mishandle size_t overflow.
* m4/calloc.m4 (_AC_FUNC_CALLOC_IF): Check for buggy calloc
implementations that mishandle size_t overflow.
--- lib/calloc.c 10 Jun 2004 08:29:26 -0000 1.1
+++ lib/calloc.c 17 Nov 2004 22:47:27 -0000
@@ -1,4 +1,4 @@
-/* Work around the condition whereby calloc (n, s) fails when n*s is 0.
+/* calloc() function that is glibc compatible.
This wrapper function is required at least on Tru64 UNIX 5.1.
Copyright (C) 2004 Free Software Foundation, Inc.
@@ -31,9 +31,17 @@
void *
rpl_calloc (size_t n, size_t s)
{
+ size_t bytes;
if (n == 0)
n = 1;
if (s == 0)
s = 1;
+
+ /* Defend against buggy calloc implementations that mishandle
+ size_t overflow. */
+ bytes = n * s;
+ if (bytes / s != n)
+ return NULL;
+
return calloc (n, s);
}
--- m4/calloc.m4 7 Aug 2004 00:09:39 -0000 1.2
+++ m4/calloc.m4 17 Nov 2004 22:47:27 -0000
@@ -1,6 +1,25 @@
-#serial 2
+# calloc.m4 serial 3
-# Determine whether calloc (N, S) returns non-NULL when N*S is zero.
+# Copyright (C) 2004 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+# Written by Jim Meyering.
+
+# Determine whether calloc (N, S) returns non-NULL when N*S is zero,
+# and returns NULL when N*S overflows.
# If so, define HAVE_CALLOC. Otherwise, define calloc to rpl_calloc
# and arrange to use a calloc wrapper function that does work in that case.
@@ -9,17 +28,11 @@
# If `calloc (0, 0)' is properly handled, run IF-WORKS, otherwise, IF-NOT.
AC_DEFUN([_AC_FUNC_CALLOC_IF],
[AC_REQUIRE([AC_HEADER_STDC])dnl
+AC_REQUIRE([AC_TYPE_SIZE_T])dnl
AC_CHECK_HEADERS(stdlib.h)
AC_CACHE_CHECK([for GNU libc compatible calloc], ac_cv_func_calloc_0_nonnull,
-[AC_RUN_IFELSE(
-[AC_LANG_PROGRAM(
-[[#if STDC_HEADERS || HAVE_STDLIB_H
-# include <stdlib.h>
-#else
-char *calloc ();
-#endif
-]],
- [exit (calloc (0, 0) ? 0 : 1);])],
+[AC_RUN_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
+ [exit (!calloc (0, 0) || calloc ((size_t) -1 / 8 + 1, 8));])],
[ac_cv_func_calloc_0_nonnull=yes],
[ac_cv_func_calloc_0_nonnull=no],
[ac_cv_func_calloc_0_nonnull=no])])
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