Gdb/Breakpoints-In-Python
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23.2.2.30 Manipulating breakpoints using Python
Python code can manipulate breakpoints via the gdb.Breakpoint
class.
A breakpoint can be created using one of the two forms of the
gdb.Breakpoint
constructor. The first one accepts a string
like one would pass to the break
(see Setting Breakpoints) and watch
(see Setting Watchpoints) commands, and can be used to
create both breakpoints and watchpoints. The second accepts separate Python
arguments similar to Explicit Locations, and can only be used to create
breakpoints.
- Function: Breakpoint.__init__ (spec [, type ][, wp_class ][, internal ][, temporary ][, qualified ])
Create a new breakpoint according to
spec
, which is a string naming the location of a breakpoint, or an expression that defines a watchpoint. The string should describe a location in a format recognized by thebreak
command (see Setting Breakpoints) or, in the case of a watchpoint, by thewatch
command (see Setting Watchpoints).The optional
type
argument specifies the type of the breakpoint to create, as defined below.The optional
wp_class
argument defines the class of watchpoint to create, iftype
isgdb.BP_WATCHPOINT
. Ifwp_class
is omitted, it defaults togdb.WP_WRITE
.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 frominfo breakpoints
(but will be listed with themaint 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
qualified
argument is a boolean that allows interpreting the function passed inspec
as a fully-qualified name. It is equivalent tobreak
’s-qualified
flag (see Linespec Locations and Explicit Locations).
- Function: Breakpoint.__init__ ([ source ][, function ][, label ][, line ], ][ internal ][, temporary ][, qualified ])
This second form of creating a new breakpoint specifies the explicit location (see Explicit Locations) using keywords. The new breakpoint will be created in the specified source file
source
, at the specifiedfunction
,label
andline
.internal
,temporary
andqualified
have the same usage as explained previously.
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.
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.stop (self)
The
gdb.Breakpoint
class can be sub-classed and, in particular, you may choose to implement thestop
method. If this method is defined in a sub-class ofgdb.Breakpoint
, it will be called when the inferior reaches any location of a breakpoint which instantiates that sub-class. If the method returnsTrue
, 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 allstop
methods have a chance to execute at that location. In this scenario if one of the methods returnsTrue
but the others returnFalse
, 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
- Function
- Breakpoint.is_valid ()
- Return
True
if thisBreakpoint
object is valid,False
otherwise. ABreakpoint
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, andFalse
otherwise. This attribute is writable. You can use it to enable or disable the breakpoint.
- Variable: Breakpoint.silent
This attribute is
True
if the breakpoint is silent, andFalse
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 thesilent
attribute.
- Variable
- Breakpoint.pending
- This attribute is
True
if the breakpoint is pending, andFalse
otherwise. See Set Breaks. This attribute is read-only.
- Variable
- Breakpoint.thread
- If the breakpoint is thread-specific, this attribute holds the thread’s global 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.
- 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 writable.
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