Re: [python][patch] Add temporary breakpoint features to Python breakpoints.

[Phil Muldoon <pmuldoon at redhat dot com>]

On 09/09/13 19:47, Tom Tromey wrote:
>>>>>> "Phil" == Phil Muldoon <pmuldoon@redhat.com> writes:

> Phil> 2013-09-09  Phil Muldoon  <pmuldoon@redhat.com>
> 
> Phil> 	* python/py-breakpoint.c (bppy_get_temporary): New function.
> Phil> 	(bppy_init): New keyword: temporary. Parse it and set breakpoint
> Phil> 	to temporary if True.
> 
> Is there a PR associated with this?
> I thought there was, but I didn't check.

I did a search and I could not find one.

> In particular I was wondering how it interacts with the "stop" method.

I added a test to make sure the "stop" method is executing before
deletion.  I think the docs are approved by both you and Eli?

Other nits fixed up too.  ChangeLog remains the same.

OK?

Cheers,

Phil

--

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 21250fe..627d65e 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -26799,22 +26799,27 @@ Return the static block of the underlying symbol table.
 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
 class.
 
-@defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
-Create a new breakpoint.  @var{spec} 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
-@code{break} command, or in the case of a watchpoint, by the @code{watch}
-command.  The optional @var{type} denotes the breakpoint to create
-from the types defined later in this chapter.  This argument can be
-either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}.  @var{type}
-defaults to @code{gdb.BP_BREAKPOINT}.  The optional @var{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 @code{info breakpoints} (but will be listed with the
-@code{maint info breakpoints} command).  The optional @var{wp_class}
-argument defines the class of watchpoint to create, if @var{type} is
-@code{gdb.BP_WATCHPOINT}.  If a watchpoint class is not provided, it is
-assumed to be a @code{gdb.WP_WRITE} class.
+@defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
+Create a new breakpoint.  @var{spec} 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 @code{break} command,
+or in the case of a watchpoint, by the @code{watch} command.  The
+optional @var{type} denotes the breakpoint to create from the types
+defined later in this chapter.  This argument can be either:
+@code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}.  @var{type}
+defaults to @code{gdb.BP_BREAKPOINT}.  The optional @var{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 @code{info breakpoints} (but will be listed
+with the @code{maint info breakpoints} command).  The optional
+@var{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 @var{wp_class} argument defines
+the class of watchpoint to create, if @var{type} is
+@code{gdb.BP_WATCHPOINT}.  If a watchpoint class is not provided, it
+is assumed to be a @code{gdb.WP_WRITE} class.
 @end defun
 
 @defun Breakpoint.stop (self)
@@ -26935,6 +26940,16 @@ when set, or when the @samp{info breakpoints} command is run.  This
 attribute is not writable.
 @end defvar
 
+@defvar 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 @code{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.
+@end defvar
+
 The available types are represented by constants defined in the @code{gdb}
 module:
 
diff --git a/gdb/python/py-breakpoint.c b/gdb/python/py-breakpoint.c
index 87f1fdc..e83471e 100644
--- a/gdb/python/py-breakpoint.c
+++ b/gdb/python/py-breakpoint.c
@@ -529,6 +529,23 @@ bppy_get_visibility (PyObject *self, void *closure)
   Py_RETURN_TRUE;
 }
 
+/* Python function to determine if the breakpoint is a temporary
+   breakpoint.  */
+
+static PyObject *
+bppy_get_temporary (PyObject *self, void *closure)
+{
+  breakpoint_object *self_bp = (breakpoint_object *) self;
+
+  BPPY_REQUIRE_VALID (self_bp);
+
+  if (self_bp->bp->disposition == disp_del
+      || self_bp->bp->disposition == disp_del_at_next_stop)
+    Py_RETURN_TRUE;
+
+  Py_RETURN_FALSE;
+}
+
 /* Python function to get the breakpoint's number.  */
 static PyObject *
 bppy_get_number (PyObject *self, void *closure)
@@ -594,16 +611,20 @@ bppy_get_ignore_count (PyObject *self, void *closure)
 static int
 bppy_init (PyObject *self, PyObject *args, PyObject *kwargs)
 {
-  static char *keywords[] = { "spec", "type", "wp_class", "internal", NULL };
+  static char *keywords[] = { "spec", "type", "wp_class", "internal",
+			      "temporary", NULL };
   const char *spec;
   int type = bp_breakpoint;
   int access_type = hw_write;
   PyObject *internal = NULL;
+  PyObject *temporary = NULL;
   int internal_bp = 0;
+  int temporary_bp = 0;
   volatile struct gdb_exception except;
 
-  if (! PyArg_ParseTupleAndKeywords (args, kwargs, "s|iiO", keywords,
-				     &spec, &type, &access_type, &internal))
+  if (! PyArg_ParseTupleAndKeywords (args, kwargs, "s|iiOO", keywords,
+				     &spec, &type, &access_type,
+				     &internal, &temporary))
     return -1;
 
   if (internal)
@@ -613,6 +634,13 @@ bppy_init (PyObject *self, PyObject *args, PyObject *kwargs)
 	return -1;
     }
 
+  if (temporary != NULL)
+    {
+      temporary_bp = PyObject_IsTrue (temporary);
+      if (temporary_bp == -1)
+	return -1;
+    }
+
   bppy_pending_object = (breakpoint_object *) self;
   bppy_pending_object->number = -1;
   bppy_pending_object->bp = NULL;
@@ -629,7 +657,7 @@ bppy_init (PyObject *self, PyObject *args, PyObject *kwargs)
 	    create_breakpoint (python_gdbarch,
 			       copy, NULL, -1, NULL,
 			       0,
-			       0, bp_breakpoint,
+			       temporary_bp, bp_breakpoint,
 			       0,
 			       AUTO_BOOLEAN_TRUE,
 			       &bkpt_breakpoint_ops,
@@ -973,6 +1001,8 @@ or None if no condition set."},
     "Type of breakpoint."},
   { "visible", bppy_get_visibility, NULL,
     "Whether the breakpoint is visible to the user."},
+  { "temporary", bppy_get_temporary, NULL,
+    "Whether this breakpoint is a temporary breakpoint."},
   { NULL }  /* Sentinel.  */
 };
 
diff --git a/gdb/testsuite/gdb.python/py-breakpoint.exp b/gdb/testsuite/gdb.python/py-breakpoint.exp
index 687182d..e2a169b 100644
--- a/gdb/testsuite/gdb.python/py-breakpoint.exp
+++ b/gdb/testsuite/gdb.python/py-breakpoint.exp
@@ -300,3 +300,37 @@ gdb_py_test_silent_cmd  "python wp1 = wp_eval (\"result\", type=gdb.BP_WATCHPOIN
 gdb_test "continue" ".*\[Ww\]atchpoint.*result.*Old value =.*New value = 788.*" "Test watchpoint write"
 gdb_test "python print (never_eval_bp1.count)" "0" \
     "Check that this unrelated breakpoints eval function was never called."
+
+# Test temporary breakpoint
+
+# Start with a fresh gdb.
+clean_restart ${testfile}
+
+if ![runto_main] then {
+    fail "Cannot run to main."
+    return 0
+}
+delete_breakpoints
+gdb_py_test_multiple "Sub-class and check temporary breakpoint" \
+  "python" "" \
+  "class temp_bp (gdb.Breakpoint):" "" \
+  "   count = 0" "" \
+  "   def stop (self):" "" \
+  "      self.count = self.count + 1" "" \
+  "      return True" "" \
+  "end" ""
+gdb_py_test_silent_cmd  "python ibp =  temp_bp(\"$ibp_location\", temporary=True)" \
+    "Set temporary breakpoint" 0
+gdb_test "info breakpoints" "2.*breakpoint.*del.*py-breakpoint\.c:$ibp_location.*" \
+    "Check info breakpoints shows breakpoint with temporary status"
+gdb_test "python print (ibp.location)" "py-breakpoint\.c:$ibp_location*" \
+    "Check temporary breakpoint location"
+gdb_test "python print (ibp.temporary)" "True" \
+    "Check breakpoint temporary status"
+gdb_continue_to_breakpoint "Break at multiply." ".*/$srcfile:$ibp_location.*"
+gdb_test "python print (ibp.count)" "1" \
+    "Check temporary stop callback executed before deletion."
+gdb_test "python print (ibp.temporary)" "RuntimeError: Breakpoint 2 is invalid.*" \
+    "Check temporary breakpoint is deleted after being hit"
+gdb_test "info breakpoints" "No breakpoints or watchpoints.*" \
+    "Check info breakpoints shows temporary breakpoint is deleted"