The DBUG Package Flag Description o Redirect the debugger output stream to the specified file. The default output is  stderr . O Like  o , but the file is really flushed between each write. When needed, the file is closed and reopened between each write. p Limit debugger actions to specified processes. A process must be identified with the  DBUG_PROCESS macro and match one in the list for debugger actions to occur. P Print the current process name for each line of debug or trace output. r When pushing a new state, do not inherit the previous state’s function nesting level. Useful when the output is to start at the left margin. S Do function  _sanity(_file_,_line_)  at each debugged function until  _sanity()  returns something that differs from 0. t Enable function call/exit trace lines. May be followed by a list (containing only one modifier) giving a numeric maximum trace level, beyond which no output occurs for either debugging or tracing macros. The default is a compile time option. mysql>  SET debug = ’d’; mysql>  SELECT @@debug; +---------+ | @@debug | +---------+ | d | +---------+ mysql>  SET debug = ’d,error,warning’; mysql>  SELECT @@debug; +-----------------+ | @@debug | +-----------------+ | d,error,warning | +-----------------+ mysql>  SET debug = ’+d,loop’; mysql>  SELECT @@debug; A leading  +  or  -  adds to or subtracts from the current  d  value: 1167 •With a leading  +  or  - , the modifiers in the list are added to or subtracted from the current modifier list. •With no leading  +  or  - , the flag value is set to exactly the modifier list as given. The leading  +  or  -  character and trailing list of modifiers are used for flag characters such as  d  or  f  that can enable a debug operation for all applicable modifiers or just some of them: The following examples show how this works for the  d  flag. An empty  d  list enabled output for all debug macros. A nonempty list enables output only for the macro keywords in the list. These statements set the  d  value to the modifier list as given: