gdb.info: Breakpoints In Python

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23.2.2.28 Manipulating breakpoints using Python
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Python code can manipulate breakpoints via the 'gdb.Breakpoint' class.

 -- Function: Breakpoint.__init__ (spec [, type [, wp_class [,internal
          [,temporary]]]])
     Create a new breakpoint according to SPEC, which is a string naming
     the location of the breakpoint, or an expression that defines a
     watchpoint.  The contents can be any location recognized by the
     'break' command, or in the case of a watchpoint, by the 'watch'
     command.  The optional TYPE denotes the breakpoint to create from
     the types defined later in this chapter.  This argument can be
     either 'gdb.BP_BREAKPOINT' or 'gdb.BP_WATCHPOINT'; it defaults to
     'gdb.BP_BREAKPOINT'.  The optional INTERNAL argument allows the
     breakpoint to become invisible to the user.  The breakpoint will
     neither be reported when created, nor will it be listed in the
     output from 'info breakpoints' (but will be listed with the 'maint
     info breakpoints' command).  The optional TEMPORARY argument makes
     the breakpoint a temporary breakpoint.  Temporary breakpoints are
     deleted after they have been hit.  Any further access to the Python
     breakpoint after it has been hit will result in a runtime error (as
     that breakpoint has now been automatically deleted).  The optional
     WP_CLASS argument defines the class of watchpoint to create, if
     TYPE is 'gdb.BP_WATCHPOINT'.  If a watchpoint class is not
     provided, it is assumed to be a 'gdb.WP_WRITE' class.

 -- Function: Breakpoint.stop (self)
     The 'gdb.Breakpoint' class can be sub-classed and, in particular,
     you may choose to implement the 'stop' method.  If this method is
     defined in a sub-class of 'gdb.Breakpoint', it will be called when
     the inferior reaches any location of a breakpoint which
     instantiates that sub-class.  If the method returns 'True', the
     inferior will be stopped at the location of the breakpoint,
     otherwise the inferior will continue.

     If there are multiple breakpoints at the same location with a
     'stop' method, each one will be called regardless of the return
     status of the previous.  This ensures that all 'stop' methods have
     a chance to execute at that location.  In this scenario if one of
     the methods returns 'True' but the others return 'False', the
     inferior will still be stopped.

     You should not alter the execution state of the inferior (i.e.,
     step, next, etc.), alter the current frame context (i.e., change
     the current active frame), or alter, add or delete any breakpoint.
     As a general rule, you should not alter any data within GDB or the
     inferior at this time.

     Example 'stop' implementation:

          class MyBreakpoint (gdb.Breakpoint):
                def stop (self):
                  inf_val = gdb.parse_and_eval("foo")
                  if inf_val == 3:
                    return True
                  return False

   The available watchpoint types represented by constants are defined
in the 'gdb' module:

'gdb.WP_READ'
     Read only watchpoint.

'gdb.WP_WRITE'
     Write only watchpoint.

'gdb.WP_ACCESS'
     Read/Write watchpoint.

 -- Function: Breakpoint.is_valid ()
     Return 'True' if this 'Breakpoint' object is valid, 'False'
     otherwise.  A 'Breakpoint' object can become invalid if the user
     deletes the breakpoint.  In this case, the object still exists, but
     the underlying breakpoint does not.  In the cases of watchpoint
     scope, the watchpoint remains valid even if execution of the
     inferior leaves the scope of that watchpoint.

 -- Function: Breakpoint.delete
     Permanently deletes the GDB breakpoint.  This also invalidates the
     Python 'Breakpoint' object.  Any further access to this object's
     attributes or methods will raise an error.

 -- Variable: Breakpoint.enabled
     This attribute is 'True' if the breakpoint is enabled, and 'False'
     otherwise.  This attribute is writable.

 -- Variable: Breakpoint.silent
     This attribute is 'True' if the breakpoint is silent, and 'False'
     otherwise.  This attribute is writable.

     Note that a breakpoint can also be silent if it has commands and
     the first command is 'silent'.  This is not reported by the
     'silent' attribute.

 -- Variable: Breakpoint.thread
     If the breakpoint is thread-specific, this attribute holds the
     thread id.  If the breakpoint is not thread-specific, this
     attribute is 'None'.  This attribute is writable.

 -- Variable: Breakpoint.task
     If the breakpoint is Ada task-specific, this attribute holds the
     Ada task id.  If the breakpoint is not task-specific (or the
     underlying language is not Ada), this attribute is 'None'.  This
     attribute is writable.

 -- Variable: Breakpoint.ignore_count
     This attribute holds the ignore count for the breakpoint, an
     integer.  This attribute is writable.

 -- Variable: Breakpoint.number
     This attribute holds the breakpoint's number -- the identifier used
     by the user to manipulate the breakpoint.  This attribute is not
     writable.

 -- Variable: Breakpoint.type
     This attribute holds the breakpoint's type -- the identifier used
     to determine the actual breakpoint type or use-case.  This
     attribute is not writable.

 -- Variable: Breakpoint.visible
     This attribute tells whether the breakpoint is visible to the user
     when set, or when the 'info breakpoints' command is run.  This
     attribute is not writable.

 -- Variable: Breakpoint.temporary
     This attribute indicates whether the breakpoint was created as a
     temporary breakpoint.  Temporary breakpoints are automatically
     deleted after that breakpoint has been hit.  Access to this
     attribute, and all other attributes and functions other than the
     'is_valid' function, will result in an error after the breakpoint
     has been hit (as it has been automatically deleted).  This
     attribute is not writable.

   The available types are represented by constants defined in the 'gdb'
module:

'gdb.BP_BREAKPOINT'
     Normal code breakpoint.

'gdb.BP_WATCHPOINT'
     Watchpoint breakpoint.

'gdb.BP_HARDWARE_WATCHPOINT'
     Hardware assisted watchpoint.

'gdb.BP_READ_WATCHPOINT'
     Hardware assisted read watchpoint.

'gdb.BP_ACCESS_WATCHPOINT'
     Hardware assisted access watchpoint.

 -- Variable: Breakpoint.hit_count
     This attribute holds the hit count for the breakpoint, an integer.
     This attribute is writable, but currently it can only be set to
     zero.

 -- Variable: Breakpoint.location
     This attribute holds the location of the breakpoint, as specified
     by the user.  It is a string.  If the breakpoint does not have a
     location (that is, it is a watchpoint) the attribute's value is
     'None'.  This attribute is not writable.

 -- Variable: Breakpoint.expression
     This attribute holds a breakpoint expression, as specified by the
     user.  It is a string.  If the breakpoint does not have an
     expression (the breakpoint is not a watchpoint) the attribute's
     value is 'None'.  This attribute is not writable.

 -- Variable: Breakpoint.condition
     This attribute holds the condition of the breakpoint, as specified
     by the user.  It is a string.  If there is no condition, this
     attribute's value is 'None'.  This attribute is writable.

 -- Variable: Breakpoint.commands
     This attribute holds the commands attached to the breakpoint.  If
     there are commands, this attribute's value is a string holding all
     the commands, separated by newlines.  If there are no commands,
     this attribute is 'None'.  This attribute is not writable.