Import reallocarray(3) from OpenBSD

Add a manpage for it, assign the copyright to the OpenBSD project on it since it
is mostly copy/paste from OpenBSD manpage.
style(9) fixes

Differential Revision:	https://reviews.freebsd.org/D2420
Reviewed by:	kib

4 files changed, 182 insertions, 2 deletions

diff --git a/lib/libc/stdlib/Makefile.inc b/lib/libc/stdlib/Makefile.inc
index 57205a7..7cee03a 100644
--- a/lib/libc/stdlib/Makefile.inc
+++ b/lib/libc/stdlib/Makefile.inc
@@ -10,7 +10,8 @@ MISRCS+=_Exit.c a64l.c abort.c abs.c atexit.c atof.c atoi.c atol.c atoll.c \
 	insque.c l64a.c labs.c ldiv.c llabs.c lldiv.c lsearch.c \
 	merge.c mergesort_b.c ptsname.c qsort.c qsort_r.c quick_exit.c \
 	radixsort.c rand.c \
-	random.c reallocf.c realpath.c remque.c strfmon.c strtoimax.c \
+	random.c reallocarray.c reallocf.c realpath.c remque.c strfmon.c \
+	strtoimax.c \
 	strtol.c strtoll.c strtoq.c strtoul.c strtonum.c strtoull.c \
         strtoumax.c strtouq.c system.c tdelete.c tfind.c tsearch.c twalk.c
 
@@ -25,7 +26,7 @@ MAN+=	a64l.3 abort.3 abs.3 alloca.3 atexit.3 atof.3 \
 	hcreate.3 imaxabs.3 imaxdiv.3 insque.3 labs.3 ldiv.3 llabs.3 lldiv.3 \
 	lsearch.3 memory.3 ptsname.3 qsort.3 \
 	quick_exit.3 \
-	radixsort.3 rand.3 random.3 reallocf.3 \
+	radixsort.3 rand.3 random.3 reallocarray.3 reallocf.3 \
 	realpath.3 strfmon.3 strtod.3 strtol.3 strtonum.3 strtoul.3 system.3 \
 	tsearch.3
 
diff --git a/lib/libc/stdlib/Symbol.map b/lib/libc/stdlib/Symbol.map
index 39eab7d..782023e 100644
--- a/lib/libc/stdlib/Symbol.map
+++ b/lib/libc/stdlib/Symbol.map
@@ -113,6 +113,7 @@ FBSD_1.4 {
 	hcreate_r;
 	hdestroy_r;
 	hsearch_r;
+	reallocarray;
 };
 
 FBSDprivate_1.0 {
diff --git a/lib/libc/stdlib/reallocarray.3 b/lib/libc/stdlib/reallocarray.3
new file mode 100644
index 0000000..1b68493
--- /dev/null
+++ b/lib/libc/stdlib/reallocarray.3
@@ -0,0 +1,136 @@
+.\" Copyright (c) 2015 OpenBSD
+.\" All rights reserved.
+.\"
+.\" This code is derived from software contributed to Berkeley by
+.\" the American National Standards Committee X3, on Information
+.\" Processing Systems.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd May 1, 2015
+.Dt REALLOCARRAY 3
+.Os
+.Sh NAME
+.Nm reallocarray
+.Nd memory reallocation function
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In stdlib.h
+.Ft void *
+.Fn reallocarray "void *ptr" "size_t nmemb" "size_t size"
+.Sh DESCRIPTION
+The
+.Fn reallocarray
+except it operates on
+.Fa nmemb
+members of size
+.Fa size
+and checks for integer overflow in the calculation
+.Fa nmemb
+*
+.Fa size .
+.Sh RETURN VALUES
+.Fn reallocarray
+return a pointer to the allocated space; otherwise, a
+.Dv NULL
+pointer is returned and
+.Va errno
+is set to
+.Er ENOMEM .
+.Sh EXAMPLES
+Consider
+.Fn reallocarray
+when there is multiplication in the
+.Fa size
+argument of
+.Fn malloc
+or
+.Fn realloc .
+For example, avoid this common idiom as it may lead to integer overflow:
+.Bd -literal -offset indent
+if ((p = malloc(num * size)) == NULL)
+	err(1, "malloc");
+.Ed
+.Pp
+A drop-in replacement is the
+.Ox
+extension
+.Fn reallocarray :
+.Bd -literal -offset indent
+if ((p = reallocarray(NULL, num, size)) == NULL)
+	err(1, "reallocarray");
+.Ed
+.Pp
+When using
+.Fn realloc ,
+be careful to avoid the following idiom:
+.Bd -literal -offset indent
+size += 50;
+if ((p = realloc(p, size)) == NULL)
+	return (NULL);
+.Ed
+.Pp
+Do not adjust the variable describing how much memory has been allocated
+until the allocation has been successful.
+This can cause aberrant program behavior if the incorrect size value is used.
+In most cases, the above sample will also result in a leak of memory.
+As stated earlier, a return value of
+.Dv NULL
+indicates that the old object still remains allocated.
+Better code looks like this:
+.Bd -literal -offset indent
+newsize = size + 50;
+if ((newp = realloc(p, newsize)) == NULL) {
+	free(p);
+	p = NULL;
+	size = 0;
+	return (NULL);
+}
+p = newp;
+size = newsize;
+.Ed
+.Pp
+As with
+.Fn malloc ,
+it is important to ensure the new size value will not overflow;
+i.e. avoid allocations like the following:
+.Bd -literal -offset indent
+if ((newp = realloc(p, num * size)) == NULL) {
+	...
+.Ed
+.Pp
+Instead, use
+.Fn reallocarray :
+.Bd -literal -offset indent
+if ((newp = reallocarray(p, num, size)) == NULL) {
+	...
+.Ed
+.Sh SEE ALSO
+.Xr realloc 3
+.Sh HISTORY
+The
+.Fn reallocf
+function first appeared in
+.Ox 5.6 .
diff --git a/lib/libc/stdlib/reallocarray.c b/lib/libc/stdlib/reallocarray.c
new file mode 100644
index 0000000..e1e9b7c
--- /dev/null
+++ b/lib/libc/stdlib/reallocarray.c
@@ -0,0 +1,42 @@
+/*	$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.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.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 *
+reallocarray(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));
+}