Re: [RFC - Python] New ObjFile event

Kevin Pouget
2011-03-29T08:22:23Z

Hello,

> Do you have copyright assignment paperwork in place?  If not, let me
> know and I can get you started.  This is a requirement before we can
> accept a non-trivial patch.

No, not yet, what I am supposed to ?

> Kevin> and, likewise, allows Python's "gdb.current_objfile ()" to return
> Kevin> the current object file.
>
> I'm ambivalent about this part.
>
> It seems to me that the objfile should be an attribute of the event.
> Also setting it globally is ok, if you really want that, but it isn't a
> necessity.

I was ambivalent about this point too; I chose "gdb.current_objfile
()" because autoloading
(http://sourceware.org/gdb/current/onlinedocs/gdb/Auto_002dloading.html)
already does it this way, and the two features are pretty similar. I
felt that it would have been strange to access "gdb.current_objfile
()" in one case, and sth like "event.new_objfile" in the other case

let me know if you agree with this perspective; it wouldn't be a big
deal to flip to the other solution otherwise

> Kevin> There is still one thing I'm not happy with in the code, it's how to
> Kevin> 'properly' access "gdbpy_current_objfile" ? I commented out "static"
> Kevin> and declared it "extern" when I needed it, but that's certainly not
> Kevin> the best way:
>
> Dropping the `static' is ok.  GDB is already full of this kind of thing.
>
> Kevin> +extern struct objfile *gdbpy_current_objfile;
>
> Should be in python-internal.h.

fixed

> Kevin> +static void
> Kevin> +python_new_objfile (struct objfile *objfile)
>
> New functions need an introductory comment.
>
> Kevin> +  /* Will be NULL when clearing the symtab. */
> Kevin> +  if (objfile)
> Kevin> +    cleanup = ensure_python_env (get_objfile_arch (objfile), current_language);
>
> Is this comment stale?  It doesn't seem relevant.  When can objfile==NULL?

I've been _once_ notified with NULL objfiles, coming from
>> gdb/symfile.c:clear_symtab_users "observer_notify_new_objfile (NULL);"

that's why I added the null-checking, but I didn't investigate what's
behind this 'clear_symtab_users' and assumed
'observer_notify_new_objfile (NULL)' justifies the verification by
itself

is it okay for you?

> Kevin> -
> Kevin> +  observer_attach_new_objfile (python_new_objfile);
> Kevin> +
>
> Gratuitous whitespace change.

removed

> Kevin> int
> Kevin> emit_new_objfile_event (struct objfile *objfile)
> Kevin> {
> Kevin>   PyObject *event;
> [...]
> Kevin>   event = create_new_objfile_event_object ();
> Kevin>   if (event)
> Kevin>     return evpy_emit_event (event, gdb_py_events.newobjfile);
> Kevin>   return -1;
>
> I think this should attach the objfile to the event object.

that's discussed above, I'm waiting for your point of view

* I added to the patch a few lines of documentation and updated the
python event test-case. The exec is now linked with a shared-library
automatically created, so that we know that the new objfile observers
have to be notified. I'm not 100% confident about the test-case
protocol, please don't hesitate to tell me if it's not resilient
enough

* I don't know how to add gdb/python/py-newobjfileevent.c and
gdb/testsuite/gdb.python/py-events-shlib.c to the CVS diff, I'll move
to git today so it should be fixed for the next patchs I send ; they
are at the bottom of the mail, separated with '----'

* I don't know if there is an 'automatic' way to update the ChangeLog
(based on CVS/GIT), or if I should do it manually ?

Cheers,

Kevin

----

? gdb/python/py-newobjfileevent.c
? gdb/testsuite/gdb.python/py-events-shlib.c
Index: gdb/Makefile.in
===================================================================
RCS file: /cvs/src/src/gdb/Makefile.in,v
retrieving revision 1.1163
diff -u -r1.1163 Makefile.in
--- gdb/Makefile.in 9 Mar 2011 06:10:37 -0000 1.1163
+++ gdb/Makefile.in 29 Mar 2011 08:08:41 -0000
@@ -296,7 +296,8 @@
py-threadevent.o \
py-type.o \
py-utils.o \
- py-value.o
+ py-value.o \
+ py-newobjfileevent.o

SUBDIR_PYTHON_SRCS = \
python/python.c \
@@ -326,7 +327,8 @@
python/py-threadevent.c \
python/py-type.c \
python/py-utils.c \
- python/py-value.c
+ python/py-value.c \
+ python/py-newobjfileevent.c
SUBDIR_PYTHON_DEPS =
SUBDIR_PYTHON_LDFLAGS=
SUBDIR_PYTHON_CFLAGS=
@@ -2110,6 +2112,11 @@
$(COMPILE) $(PYTHON_CFLAGS) $(srcdir)/python/py-value.c
$(POSTCOMPILE)

+py-newobjfileevent.o: $(srcdir)/python/py-newobjfileevent.c
+ $(COMPILE) $(PYTHON_CFLAGS) $(srcdir)/python/py-newobjfileevent.c
+ $(POSTCOMPILE)
+
+
#
# Dependency tracking. Most of this is conditional on GNU Make being
# found by configure; if GNU Make is not found, we fall back to a
Index: gdb/doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.814
diff -u -r1.814 gdb.texinfo
--- gdb/doc/gdb.texinfo 18 Mar 2011 08:44:46 -0000 1.814
+++ gdb/doc/gdb.texinfo 29 Mar 2011 08:08:45 -0000
@@ -22054,6 +22054,12 @@
This event indicates that the inferior or one of its threads has received as
signal. @code{gdb.SignalEvent} has the following attributes:

+@item events.newobjfile
+Emits @code{gdb.NewObjFileEvent} which indicates that a new object-file has
+been loaded in the inferior.
+
+During the callback, ``current objfile'' will be set to the new object file.
+
@table @code
@defivar SignalEvent stop_signal
A string representing the signal received by the inferior. A list of possible
@@ -22696,10 +22702,10 @@

@findex gdb.current_objfile
@defun current_objfile
-When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
-sets the ``current objfile'' to the corresponding objfile. This
-function returns the current objfile. If there is no current objfile,
-this function returns @code{None}.
+When auto-loading a Python script (@pxref{Auto-loading}) and during new
+object-file callbacks, @value{GDBN} sets the ``current objfile'' to the
+corresponding objfile. This function returns the current objfile. If
+there is no current objfile, this function returns @code{None}.
@end defun

@findex gdb.objfiles
Index: gdb/python/py-event.h
===================================================================
RCS file: /cvs/src/src/gdb/python/py-event.h,v
retrieving revision 1.1
diff -u -r1.1 py-event.h
--- gdb/python/py-event.h 5 Feb 2011 05:27:23 -0000 1.1
+++ gdb/python/py-event.h 29 Mar 2011 08:08:46 -0000
@@ -105,6 +105,7 @@

extern int emit_continue_event (ptid_t ptid);
extern int emit_exited_event (LONGEST exit_code);
+extern int emit_new_objfile_event (struct objfile *objfile);

extern int evpy_emit_event (PyObject *event,
eventregistry_object *registry);
Index: gdb/python/py-events.h
===================================================================
RCS file: /cvs/src/src/gdb/python/py-events.h,v
retrieving revision 1.1
diff -u -r1.1 py-events.h
--- gdb/python/py-events.h 5 Feb 2011 05:27:23 -0000 1.1
+++ gdb/python/py-events.h 29 Mar 2011 08:08:46 -0000
@@ -45,6 +45,7 @@
eventregistry_object *stop;
eventregistry_object *cont;
eventregistry_object *exited;
+ eventregistry_object *newobjfile;

PyObject *module;

Index: gdb/python/py-evts.c
===================================================================
RCS file: /cvs/src/src/gdb/python/py-evts.c,v
retrieving revision 1.2
diff -u -r1.2 py-evts.c
--- gdb/python/py-evts.c 14 Mar 2011 15:43:51 -0000 1.2
+++ gdb/python/py-evts.c 29 Mar 2011 08:08:46 -0000
@@ -57,6 +57,9 @@

if (add_new_registry (&gdb_py_events.exited, "exited") < 0)
goto fail;
+
+ if (add_new_registry (&gdb_py_events.newobjfile, "newobjfile") < 0)
+ goto fail;

Py_INCREF (gdb_py_events.module);
if (PyModule_AddObject (gdb_module,
Index: gdb/python/py-inferior.c
===================================================================
RCS file: /cvs/src/src/gdb/python/py-inferior.c,v
retrieving revision 1.7
diff -u -r1.7 py-inferior.c
--- gdb/python/py-inferior.c 17 Mar 2011 09:36:16 -0000 1.7
+++ gdb/python/py-inferior.c 29 Mar 2011 08:08:46 -0000
@@ -22,6 +22,7 @@
#include "gdbcore.h"
#include "gdbthread.h"
#include "inferior.h"
+#include "objfiles.h"
#include "observer.h"
#include "python-internal.h"
#include "arch-utils.h"
@@ -129,6 +130,31 @@
do_cleanups (cleanup);
}

+/* Callback used to notify Python listeners about new objfiles loaded in the
+ inferior. Python global variable 'gdb.current_objfile ()' will be set
+ during the notifications.
+ */
+
+static void
+python_new_objfile (struct objfile *objfile)
+{
+ struct cleanup *cleanup;
+
+ /* Will be NULL when clearing the symtab. */
+ if (objfile)
+ cleanup = ensure_python_env (get_objfile_arch (objfile), current_language);
+ else
+ cleanup = ensure_python_env (get_current_arch (), current_language);
+
+ gdbpy_current_objfile = objfile;
+
+ if (emit_new_objfile_event (objfile) < 0)
+ gdbpy_print_stack ();
+
+ do_cleanups (cleanup);
+ gdbpy_current_objfile = NULL;
+}
+
/* Return a borrowed reference to the Python object of type Inferior
representing INFERIOR. If the object has already been created,
return it, otherwise, create it. Return NULL on failure. */
@@ -669,6 +695,7 @@
observer_attach_normal_stop (python_on_normal_stop);
observer_attach_target_resumed (python_on_resume);
observer_attach_inferior_exit (python_inferior_exit);
+ observer_attach_new_objfile (python_new_objfile);

if (PyType_Ready (&membuf_object_type) < 0)
return;
Index: gdb/python/python-internal.h
===================================================================
RCS file: /cvs/src/src/gdb/python/python-internal.h,v
retrieving revision 1.44
diff -u -r1.44 python-internal.h
--- gdb/python/python-internal.h 28 Feb 2011 19:38:34 -0000 1.44
+++ gdb/python/python-internal.h 29 Mar 2011 08:08:46 -0000
@@ -207,6 +207,7 @@
void gdbpy_initialize_continue_event (void);
void gdbpy_initialize_exited_event (void);
void gdbpy_initialize_thread_event (void);
+void gdbpy_initialize_new_objfile_event (void);

struct cleanup *make_cleanup_py_decref (PyObject *py);

@@ -215,6 +216,7 @@

extern struct gdbarch *python_gdbarch;
extern const struct language_defn *python_language;
+extern struct objfile *gdbpy_current_objfile;

/* Use this after a TRY_EXCEPT to throw the appropriate Python
exception. */
Index: gdb/python/python.c
===================================================================
RCS file: /cvs/src/src/gdb/python/python.c,v
retrieving revision 1.63
diff -u -r1.63 python.c
--- gdb/python/python.c 18 Mar 2011 08:44:47 -0000 1.63
+++ gdb/python/python.c 29 Mar 2011 08:08:46 -0000
@@ -811,8 +811,9 @@

/* The "current" objfile. This is set when gdb detects that a new
objfile has been loaded. It is only set for the duration of a call to
- source_python_script_for_objfile; it is NULL at other times. */
-static struct objfile *gdbpy_current_objfile;
+ source_python_script_for_objfile and new_objfile callbacks; it is NULL at
+ other times. */
+struct objfile *gdbpy_current_objfile;

/* Set the current objfile to OBJFILE and then read STREAM,FILE as
Python code. */
@@ -1074,6 +1075,7 @@
gdbpy_initialize_continue_event ();
gdbpy_initialize_exited_event ();
gdbpy_initialize_thread_event ();
+ gdbpy_initialize_new_objfile_event () ;

PyRun_SimpleString ("import gdb");
PyRun_SimpleString ("gdb.pretty_printers = []");
Index: gdb/testsuite/gdb.python/py-events.c
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.python/py-events.c,v
retrieving revision 1.1
diff -u -r1.1 py-events.c
--- gdb/testsuite/gdb.python/py-events.c 5 Feb 2011 05:27:23 -0000 1.1
+++ gdb/testsuite/gdb.python/py-events.c 29 Mar 2011 08:08:46 -0000
@@ -16,6 +16,8 @@
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

+extern void do_nothing (void) ;
+
int second(){
return 12;
}
@@ -25,5 +27,6 @@
}

int main (){
+ do_nothing() ;
return first();
}
Index: gdb/testsuite/gdb.python/py-events.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.python/py-events.exp,v
retrieving revision 1.1
diff -u -r1.1 py-events.exp
--- gdb/testsuite/gdb.python/py-events.exp 5 Feb 2011 05:27:23 -0000 1.1
+++ gdb/testsuite/gdb.python/py-events.exp 29 Mar 2011 08:08:46 -0000
@@ -24,23 +24,45 @@

load_lib gdb-python.exp

+set libfile "py-events-shlib"
+set libsrc $srcdir/$subdir/$libfile.c
+set lib_sl $objdir/$subdir/$libfile.so
+set lib_opts debug
+
set testfile "py-events"
set srcfile ${testfile}.c
set binfile ${objdir}/${subdir}/${testfile}
+set exec_opts [list debug shlib=$lib_sl]
set pyfile ${srcdir}/${subdir}/${testfile}.py

-if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
+if [get_compiler_info ${binfile}] {
+ return -1
+}
+
+if { [gdb_compile_shlib $libsrc $lib_sl $lib_opts] != ""
+ || [gdb_compile $srcdir/$subdir/$srcfile $binfile executable
$exec_opts] != ""} {
+ untested "Could not compile either $libsrc or $srcdir/$subdir/$srcfile."
return -1
}

+# Start with a fresh gdb.
+
+gdb_exit
+gdb_start
+
if { [skip_python_tests] } { continue }

+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
gdb_test_no_output "python execfile ('${pyfile}')" ""

-if ![runto_main ] then {
- fail "Can't run to main"
- return -1
-}
+gdb_test "Test_Newobj_Events" "New ObjectFile Event tester registered."
+
+gdb_breakpoint "main" {temporary}
+
+gdb_test "run" ".*event type: new_objfile.*
+.*new objfile name.*"

gdb_test "Test_Events" "Event testers registered."

Index: gdb/testsuite/gdb.python/py-events.py
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.python/py-events.py,v
retrieving revision 1.1
diff -u -r1.1 py-events.py
--- gdb/testsuite/gdb.python/py-events.py 5 Feb 2011 05:27:23 -0000 1.1
+++ gdb/testsuite/gdb.python/py-events.py 29 Mar 2011 08:08:46 -0000
@@ -48,6 +48,14 @@
if ( event.inferior_thread is not None) :
print "thread num: %s" % (event.inferior_thread.num);

+def new_objfile_handler (event):
+ if (isinstance (event, gdb.NewObjFileEvent)):
+ print "event type: new_objfile"
+ if (gdb.current_objfile () is not None):
+ print "new objfile name: %s" % (gdb.current_objfile ().filename)
+ else:
+ print "new objfile is None"
+
class test_events (gdb.Command):
"""Test events."""

@@ -62,3 +70,15 @@
print "Event testers registered."

test_events ()
+
+class test_newobj_events (gdb.Command):
+ """NewObj events."""
+
+ def __init__ (self):
+ gdb.Command.__init__ (self, "test_newobj_events", gdb.COMMAND_STACK)
+
+ def invoke (self, arg, from_tty):
+ gdb.events.newobjfile.connect (new_objfile_handler)
+ print "New ObjectFile Event tester registered."
+
+test_newobj_events ()

----

/* Python interface to new object file loading events.

Copyright (C) 2011 Free Software Foundation, Inc.

This file is part of GDB.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */

#include "py-event.h"

static PyTypeObject new_objfile_event_object_type;

PyObject *
create_new_objfile_event_object (void)
{
return create_event_object (&new_objfile_event_object_type);
}

/* Callback function which notifies observers when a new objfile event occurs.
This function will create a new Python new_objfile event object.
Return -1 if emit fails. */

int
emit_new_objfile_event (struct objfile *objfile)
{
PyObject *event;

if (evregpy_no_listeners_p (gdb_py_events.newobjfile))
return 0;

event = create_new_objfile_event_object ();
if (event)
return evpy_emit_event (event, gdb_py_events.newobjfile);
return -1;
}

GDBPY_NEW_EVENT_TYPE (new_objfile,
"gdb.NewObjFileEvent",
"NewObjFileEvent",
"GDB new object file event object",
event_object_type,
static);

----

/* This testcase is part of GDB, the GNU debugger.

Copyright 2011 Free Software Foundation, Inc.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */

void do_nothing (void) {}