NetBSD re-synchronization of the source tree

This brings our tree to NetBSD 7.0, as found on -current on the
10-10-2015.

This updates:
 - LLVM to 3.6.1
 - GCC to GCC 5.1
 - Replace minix/commands/zdump with usr.bin/zdump
 - external/bsd/libelf has moved to /external/bsd/elftoolchain/
 - Import ctwm
 - Drop sprintf from libminc

Change-Id: I149836ac18e9326be9353958bab9b266efb056f0

lib/libc/stdlib/malloc.3

@@ -1,4 +1,4 @@
-.\" $NetBSD: malloc.3,v 1.38 2010/05/03 08:23:20 jruoho Exp $
+.\" $NetBSD: malloc.3,v 1.44 2015/07/26 22:32:03 wiz Exp $
 .\"
 .\" Copyright (c) 1980, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -34,7 +34,7 @@
 .\"     @(#)malloc.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD: src/lib/libc/stdlib/malloc.3,v 1.73 2007/06/15 22:32:33 jasone Exp $
 .\"
-.Dd May 3, 2010
+.Dd July 26, 2015
 .Dt MALLOC 3
 .Os
 .Sh NAME
@@ -90,6 +90,7 @@ the value of the newly allocated portion of the memory is undefined.
 Upon success, the memory referenced by
 .Fa ptr
 is freed and a pointer to the newly allocated memory is returned.
+.Pp
 Note that
 .Fn realloc
 may move the memory allocation, resulting in a different return value than
@@ -158,7 +159,7 @@ if ((p = malloc(number * size)) == NULL)
 .Pp
 The multiplication may lead to an integer overflow.
 To avoid this,
-.Fn calloc
+.Xr reallocarr 3
 is recommended.
 .Pp
 If
@@ -171,10 +172,46 @@ if (size && number > SIZE_MAX / size) {
 }
 .Ed
 .Pp
+The above test is not sufficient in all cases.
+For example, multiplying ints requires a different set of checks:
+.Bd -literal -offset indent
+int num, size;
+\&.\&.\&.
+
+/* Avoid invalid requests */
+if (size < 0 || num < 0)
+	errc(1, EOVERFLOW, "overflow");
+
+/* Check for signed int overflow */
+if (size && num > INT_MAX / size)
+	errc(1, EOVERFLOW, "overflow");
+
+if ((p = malloc(size * num)) == NULL)
+	err(1, "malloc");
+.Ed
+.Pp
+Assuming the implementation checks for integer overflow as
+.Nx
+does, it is much easier to use
+.Fn calloc
+or
+.Xr reallocarr 3 .
+.Pp
+The above examples could be simplified to:
+.Bd -literal -offset indent
+ptr = NULL;
+if ((e = reallocarr(&ptr, num, size)))
+	errx(1, "reallocarr", strerror(e));
+.Ed
+.Bd -literal -offset indent
+or at the cost of initialization:
+if ((p = calloc(num, size)) == NULL)
+	err(1, "calloc");
+.Ed
+.Pp
 When using
 .Fn realloc ,
 one must be careful to avoid the following idiom:
-.Pp
 .Bd -literal -offset indent
 nsize += 50;
 
@@ -214,7 +251,8 @@ size = newsize;
 .Xr atexit 3 ,
 .Xr getpagesize 3 ,
 .Xr memory 3 ,
-.Xr posix_memalign 3
+.Xr posix_memalign 3 ,
+.Xr reallocarr 3
 .Pp
 For the implementation details, see
 .Xr jemalloc 3 .
@@ -227,3 +265,47 @@ and
 .Fn free
 functions conform to
 .St -isoC .
+.Sh HISTORY
+A
+.Fn free
+internal kernel function and a predecessor to
+.Fn malloc ,
+.Fn alloc ,
+first appeared in
+.At v1 .
+The C Library functions
+.Fn alloc
+and
+.Fn free
+appeared in
+.At v6 .
+The functions
+.Fn malloc ,
+.Fn calloc ,
+and
+.Fn realloc
+first appeared in
+.At v7 .
+.Pp
+A new implementation by Chris Kingsley was introduced in
+.Bx 4.2 ,
+followed by a complete rewrite by Poul-Henning Kamp
+.Dq ( phk's malloc
+or
+.Dq new malloc )
+which appeared in
+.Fx 2.2
+and was included in
+.Nx 1.5
+and
+.Ox 2.0 .
+These implementations were all
+.Xr sbrk 2
+based.
+.Pp
+The
+.Xr jemalloc 3
+allocator became the default system allocator first in
+.Fx 7.0
+and then in
+.Nx 5.0 .