Import reallocarray() from OpenBSD

Wrapper for realloc() that checks for overflow when multiplying
arguments together, so we don't have to add overflow checks to
every single call.  For documentation on usage, see:
http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man3/calloc.3

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>

configure.ac

@@ -145,6 +145,7 @@ AC_CHECK_HEADERS([sys/select.h])
 
 # Checks for library functions.
 AC_CHECK_FUNCS([strtol seteuid])
+AC_REPLACE_FUNCS([reallocarray])
 # Used in lcFile.c (see also --enable-xlocaledir settings below)
 XLOCALEDIR_IS_SAFE="no"
 AC_CHECK_DECL([issetugid])

src/Makefile.am

@@ -366,6 +366,7 @@ endif
 libX11_la_LDFLAGS = -version-number 6:3:0 -no-undefined
 
 libX11_la_LIBADD = \
+	$(LTLIBOBJS) \
 	$(USE_I18N_LIBS) \
 	$(USE_XCMS_LIBS) \
 	$(USE_XKB_LIBS) \

src/reallocarray.c

@@ -0,0 +1,43 @@
+/*	$OpenBSD: reallocarray.c,v 1.2 2014/12/08 03:45:00 bcook Exp $	*/
+/*
+ * Copyright (c) 2008 Otto Moerbeek <otto@drijf.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <sys/types.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include "reallocarray.h"
+
+/*
+ * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
+ * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
+ */
+#define MUL_NO_OVERFLOW	((size_t)1 << (sizeof(size_t) * 4))
+
+void *
+xreallocarray(void *optr, size_t nmemb, size_t size)
+{
+	if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
+	    nmemb > 0 && SIZE_MAX / nmemb < size) {
+		errno = ENOMEM;
+		return NULL;
+	}
+	return realloc(optr, size * nmemb);
+}

src/reallocarray.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <sys/types.h>
+#include <stdlib.h>
+#include <X11/Xfuncproto.h>
+
+#ifndef HAVE_REALLOCARRAY
+extern _X_HIDDEN void *xreallocarray(void *optr, size_t nmemb, size_t size);
+# define reallocarray(ptr, n, size)	xreallocarray((ptr), (n), (size))
+#endif
+
+#if defined(MALLOC_0_RETURNS_NULL) || defined(__clang_analyzer__)
+# define Xreallocarray(ptr, n, size) \
+    reallocarray((ptr), ((n) == 0 ? 1 : (n)), size)
+#else
+# define Xreallocarray(ptr, n, size)	reallocarray((ptr), (n), (size))
+#endif
+
+#define Xmallocarray(n, size)		Xreallocarray(NULL, (n), (size))