4229 mdb hangs on exit when long umem cache names exist
Reviewed by: Robert Mustacchi <rm@joyent.com>

*** 21,44 ****
   */
  /*
   * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
  #ifndef _MDB_NV_H
  #define _MDB_NV_H
  
- #pragma ident   "%Z%%M% %I%     %E% SMI"
- 
  #include <sys/types.h>
  
  #ifdef  __cplusplus
  extern "C" {
  #endif
  
  #ifdef _MDB
  
  #define MDB_NV_NAMELEN  31      /* Max variable name length including null */
  
  /*
   * These flags are stored inside each variable in v_flags:
   */
--- 21,50 ----
   */
  /*
   * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
+ /*
+  * Copyright (c) 2013 Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
+  */
  
  #ifndef _MDB_NV_H
  #define _MDB_NV_H
  
  #include <sys/types.h>
  
  #ifdef  __cplusplus
  extern "C" {
  #endif
  
  #ifdef _MDB
  
+ /*
+  * There used to be a cap (MDB_NV_NAMELEN bytes including null) on the
+  * length of variable names stored in-line.  This cap is no longer there,
+  * however parts of mdb use the constant to sanitize input.
+  */
  #define MDB_NV_NAMELEN  31      /* Max variable name length including null */
  
  /*
   * These flags are stored inside each variable in v_flags:
   */
*** 72,83 ****
   * Each variable is defined by the following variable-length structure.
   * The debugger uses name/value collections to hash almost everything, so
   * we make a few simple space optimizations:
   *
   * A variable's name can be a pointer to external storage (v_ename and
!  * MDB_NV_EXTNAME set), or it can be stored locally (MDB_NV_NAMELEN - 1
!  * bytes of storage are allocated immediately after v_lname[0]).
   *
   * A variable may have multiple definitions (v_ndef chain), but this feature
   * is mutually exclusive with MDB_NV_EXTNAME in order to save space.
   */
  typedef struct mdb_var {
--- 78,89 ----
   * Each variable is defined by the following variable-length structure.
   * The debugger uses name/value collections to hash almost everything, so
   * we make a few simple space optimizations:
   *
   * A variable's name can be a pointer to external storage (v_ename and
!  * MDB_NV_EXTNAME set), or it can be stored locally (bytes of storage are
!  * allocated immediately after v_lname[0]).
   *
   * A variable may have multiple definitions (v_ndef chain), but this feature
   * is mutually exclusive with MDB_NV_EXTNAME in order to save space.
   */
  typedef struct mdb_var {