WL#2936

"Server variables for plugins"
  Post review fixes.


client/mysql.cc:
  wl2936 "Plugin server variables" post review fixes
  compile fix. app_type is now a void* and it isn't actually used here.
include/my_getopt.h:
  wl2936 "Plugin server variables" post review fixes
  make app_type into a void*. This also required changes to 
  client/mysql.cc and storage/ndb/src/mgmsrv/InitConfigFileParser.cpp
  in order to compile.
include/my_global.h:
  wl2936 "Plugin server variables" post-review fixes
  declare compile_time_assert() macro.
  (provided by serg)
include/mysql/plugin.h:
  wl2936 "Plugin server variables" post review fixes
  Add comments
mysys/array.c:
  wl2936 "Plugin server variables" post review fixes
mysys/typelib.c:
  wl2936 "Plugin server variables" post review fixes
  find_typeset() should not alter string
sql/set_var.cc:
  wl2936 "Plugin server variables" post review fixes
  remove unnecessary code.
sql/sql_class.cc:
  wl2936 "Plugin server variables" post review fixes
  explicitly declare export style for functions.
sql/sql_lex.cc:
  wl2936 "Plugin server variables" post review fixes
  enforce that lex::plugins_static_buffer is declared immediately after
  lex::plugins.
sql/sql_plugin.cc:
  wl2936 "Plugin Server variables" post review fixes
    sys_var_pluginvar does not need st_plugin_int at construction.
    remove debug code which was accidentially committed.
    add comments.
    fix mutex lock order.
sql/sql_plugin.h:
  wl2936 "Plugin server variables" post review fixes
  add comment and macro to compare plugin_refs
sql/table.cc:
  wl2936 "plugin server variables" post review fixes
  remove unneccessary unlock and variable.
  add checks for legacy type validity
storage/ndb/src/mgmsrv/InitConfigFileParser.cpp:
  wl2936 "plugin server variables" post review fixes
  fix compile failure now that my_option::app_type is a void*

include/mysql/plugin.h

@@ -122,9 +122,43 @@ typedef int (*mysql_show_var_func)(MYSQL_THD, struct st_mysql_show_var*, char *)
 struct st_mysql_sys_var;
 struct st_mysql_value;
 
+/*
+  SYNOPSIS
+    (*mysql_var_check_func)()
+      thd               thread handle
+      var               dynamic variable being altered
+      save              pointer to temporary storage
+      value             user provided value
+  RETURN
+    0   user provided value is OK and the update func may be called.
+    any other value indicates error.
+  
+  This function should parse the user provided value and store in the
+  provided temporary storage any data as required by the update func.
+  There is sufficient space in the temporary storage to store a double.
+  Note that the update func may not be called if any other error occurs
+  so any memory allocated should be thread-local so that it may be freed
+  automatically at the end of the statement.
+*/
+
 typedef int (*mysql_var_check_func)(MYSQL_THD thd,
                                     struct st_mysql_sys_var *var,
                                     void *save, struct st_mysql_value *value);
+
+/*
+  SYNOPSIS
+    (*mysql_var_update_func)()
+      thd               thread handle
+      var               dynamic variable being altered
+      var_ptr           pointer to dynamic variable
+      save              pointer to temporary storage
+   RETURN
+     NONE
+   
+   This function should use the validated value stored in the temporary store
+   and persist it in the provided pointer to the dynamic variable.
+   For example, strings may require memory to be allocated.
+*/
 typedef void (*mysql_var_update_func)(MYSQL_THD thd,
                                       struct st_mysql_sys_var *var,
                                       void *var_ptr, void *save);
@@ -582,6 +616,10 @@ struct st_mysql_information_schema
   st_mysql_value struct for reading values from mysqld.
   Used by server variables framework to parse user-provided values.
   Will be used for arguments when implementing UDFs.
+
+  Note that val_str() returns a string in temporary memory
+  that will be freed at the end of statement. Copy the string
+  if you need it to persist.
 */
 
 #define MYSQL_VALUE_TYPE_STRING 0