[v4,2/2] gdb: Do autoload before notifying Python side in new_objfile event

Message ID 20210422154411.2788874-3-m.weghorn@posteo.de
State New
Headers show
Series
  • Make sure autoload happens before notifying Python side in new_objfile event
Related show

Commit Message

Konstantin Kharlamov via Gdb-patches April 22, 2021, 3:44 p.m.
Without any explicit dependencies specified, the observers attached
to the 'gdb::observers::new_objfile' observable are always notified
in the order in which they have been attached.

The new_objfile observer callback to auto-load scripts is attached in
'_initialize_auto_load'.
The new_objfile observer callback that propagates the new_objfile event
to the Python side is attached in 'gdbpy_initialize_inferior', which is
called via '_initialize_python'.
With '_initialize_python' happening before '_initialize_auto_load',
the consequence was that the new_objfile event was emitted on the Python
side before autoloaded scripts had been executed when a new objfile was
loaded.
As a result, trying to access the objfile's pretty printers (defined in
the autoloaded script) from a handler for the Python-side
'new_objfile' event would fail. Those would only be initialized later on
(when the 'auto_load_new_objfile' callback was called).

To make sure that the objfile passed to the Python event handler
is properly initialized (including its 'pretty_printers' member),
make sure that the 'auto_load_new_objfile' observer is notified
before the 'python_new_objfile' one that propagates the event
to the Python side.

To do this, make use of the mechanism to explicitly specify
dependencies between observers (introduced in a preparatory commit).

Add a corresponding testcase that involves a test library with an autoloaded
Python script and a handler for the Python 'new_objfile' event.

(The real world use case where I came across this issue was in an attempt
to extend handling for GDB pretty printers for dynamically loaded
objfiles in the Qt Creator IDE, s. [1] and [2] for more background.)

[1] https://bugreports.qt.io/browse/QTCREATORBUG-25339
[2] https://codereview.qt-project.org/c/qt-creator/qt-creator/+/333857/1

Tested on x86_64-linux (Debian testing).

gdb/ChangeLog:

        * gdb/auto-load.c (_initialize_auto_load): 'Specify token
        when attaching the 'auto_load_new_objfile' observer, so
        other observers can specify it as a dependency.

        * gdb/auto-load.h (struct token): Declare
        'auto_load_new_objfile_observer_token' as token to be used
        for the 'auto_load_new_objfile' observer.
        * gdb/python/py-inferior.c (gdbpy_initialize_inferior): Make
        'python_new_objfile' observer depend on 'auto_load_new_objfile'
        observer, so it gets notified after the latter.

gdb/testsuite/ChangeLog:

        * gdb.python/libpy-autoloaded-pretty-printers-in-newobjfile-event.so-gdb.py: New test.
        * gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.cc: New test.
        * gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.h: New test.
        * gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-main.cc: New test.
        * gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.exp: New test.
        * gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.py: New test.
---
 gdb/auto-load.c                               |  7 +-
 gdb/auto-load.h                               |  8 ++
 gdb/python/py-inferior.c                      |  7 +-
 ...tty-printers-in-newobjfile-event.so-gdb.py | 44 +++++++++
 ...pretty-printers-in-newobjfile-event-lib.cc | 26 +++++
 ...-pretty-printers-in-newobjfile-event-lib.h | 31 ++++++
 ...retty-printers-in-newobjfile-event-main.cc | 23 +++++
 ...ed-pretty-printers-in-newobjfile-event.exp | 96 +++++++++++++++++++
 ...ded-pretty-printers-in-newobjfile-event.py | 34 +++++++
 9 files changed, 273 insertions(+), 3 deletions(-)
 create mode 100644 gdb/testsuite/gdb.python/libpy-autoloaded-pretty-printers-in-newobjfile-event.so-gdb.py
 create mode 100644 gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.cc
 create mode 100644 gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.h
 create mode 100644 gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-main.cc
 create mode 100644 gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.exp
 create mode 100644 gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.py

-- 
2.30.2

Patch

diff --git a/gdb/auto-load.c b/gdb/auto-load.c
index 239efa34606..d2723c2573d 100644
--- a/gdb/auto-load.c
+++ b/gdb/auto-load.c
@@ -1494,6 +1494,8 @@  found and/or loaded."),
   return &retval;
 }
 
+gdb::observers::token auto_load_new_objfile_observer_token;
+
 void _initialize_auto_load ();
 void
 _initialize_auto_load ()
@@ -1503,8 +1505,9 @@  _initialize_auto_load ()
   char *guile_name_help;
   const char *suffix;
 
-  gdb::observers::new_objfile.attach (auto_load_new_objfile, "auto-load");
-
+  gdb::observers::new_objfile.attach (auto_load_new_objfile,
+                                      auto_load_new_objfile_observer_token,
+                                      "auto-load");
   add_setshow_boolean_cmd ("gdb-scripts", class_support,
 			   &auto_load_gdb_scripts, _("\
 Enable or disable auto-loading of canned sequences of commands scripts."), _("\
diff --git a/gdb/auto-load.h b/gdb/auto-load.h
index f726126c554..2f40ef5d3f1 100644
--- a/gdb/auto-load.h
+++ b/gdb/auto-load.h
@@ -25,6 +25,10 @@  struct program_space;
 struct auto_load_pspace_info;
 struct extension_language_defn;
 
+namespace gdb::observers {
+struct token;
+}
+
 /* Value of the 'set debug auto-load' configuration variable.  */
 
 extern bool debug_auto_load;
@@ -40,6 +44,10 @@  extern bool auto_load_local_gdbinit;
 extern char *auto_load_local_gdbinit_pathname;
 extern bool auto_load_local_gdbinit_loaded;
 
+/* Token used for the auto_load_new_objfile observer, so other observers can
+ * specify it as a dependency. */
+extern gdb::observers::token auto_load_new_objfile_observer_token;
+
 extern struct auto_load_pspace_info *
   get_auto_load_pspace_data_for_loading (struct program_space *pspace);
 extern void auto_load_objfile_script (struct objfile *objfile,
diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index c2861ccb735..febd2a73ece 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -18,6 +18,7 @@ 
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "defs.h"
+#include "auto-load.h"
 #include "gdbcore.h"
 #include "gdbthread.h"
 #include "inferior.h"
@@ -917,7 +918,11 @@  gdbpy_initialize_inferior (void)
   gdb::observers::register_changed.attach (python_on_register_change,
 					   "py-inferior");
   gdb::observers::inferior_exit.attach (python_inferior_exit, "py-inferior");
-  gdb::observers::new_objfile.attach (python_new_objfile, "py-inferior");
+  /* Need to run after auto-load's new_objfile observer, so that
+     auto-loaded pretty-printers are available.  */
+  gdb::observers::new_objfile.attach
+    (python_new_objfile, "py-inferior",
+     { &auto_load_new_objfile_observer_token });
   gdb::observers::inferior_added.attach (python_new_inferior, "py-inferior");
   gdb::observers::inferior_removed.attach (python_inferior_deleted,
 					   "py-inferior");
diff --git a/gdb/testsuite/gdb.python/libpy-autoloaded-pretty-printers-in-newobjfile-event.so-gdb.py b/gdb/testsuite/gdb.python/libpy-autoloaded-pretty-printers-in-newobjfile-event.so-gdb.py
new file mode 100644
index 00000000000..2327e4a7384
--- /dev/null
+++ b/gdb/testsuite/gdb.python/libpy-autoloaded-pretty-printers-in-newobjfile-event.so-gdb.py
@@ -0,0 +1,44 @@ 
+# Copyright (C) 2021 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/>.
+
+# This file is part of the GDB testsuite. It tests that python pretty
+# printers defined in a python script that is autoloaded have been
+# registered when a custom event handler for the new_objfile event
+# is called.
+
+import gdb.printing
+
+
+class MyClassTestLibPrinter(object):
+    "Print a MyClassTestLib"
+
+    def __init__(self, val):
+        self.val = val
+
+    def to_string(self):
+        return "MyClassTestLib object, id: {}".format(self.val['id'])
+
+    def display_hint(self):
+        return "string"
+
+
+def build_pretty_printer():
+    pp = gdb.printing.RegexpCollectionPrettyPrinter(
+        "my_library")
+    pp.add_printer("MyClassTestLib", "^MyClassTestLib$", MyClassTestLibPrinter)
+    return pp
+
+
+gdb.printing.register_pretty_printer(gdb.current_objfile(), build_pretty_printer())
diff --git a/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.cc b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.cc
new file mode 100644
index 00000000000..7e06cf3903f
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.cc
@@ -0,0 +1,26 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2021 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/>.  */
+
+#include "py-autoloaded-pretty-printers-in-newobjfile-event-lib.h"
+
+MyClassTestLib::MyClassTestLib(int theId) {
+    id = theId;
+}
+
+int MyClassTestLib::getId() {
+    return id;
+}
diff --git a/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.h b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.h
new file mode 100644
index 00000000000..fa2501bf6de
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-lib.h
@@ -0,0 +1,31 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2021 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/>.  */
+
+#ifndef TESTLIBRARY_H
+#define TESTLIBRARY_H
+
+class MyClassTestLib {
+
+public:
+    explicit MyClassTestLib(int theId);
+    int getId();
+
+private:
+    int id;
+};
+
+#endif // TESTLIBRARY_H
diff --git a/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-main.cc b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-main.cc
new file mode 100644
index 00000000000..6e66bbe3d43
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event-main.cc
@@ -0,0 +1,23 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2021 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/>.  */
+
+#include "py-autoloaded-pretty-printers-in-newobjfile-event-lib.h"
+
+int main() {
+    MyClassTestLib test(1);
+    return 0; /* break to inspect */
+}
diff --git a/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.exp b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.exp
new file mode 100644
index 00000000000..ed1c3230835
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.exp
@@ -0,0 +1,96 @@ 
+# Copyright (C) 2021 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/>.
+
+# This file is part of the GDB testsuite. It tests that python pretty
+# printers defined in a python script that is autoloaded have been
+# registered when a custom event handler for the new_objfile event
+# is called.
+
+if [use_gdb_stub] {
+    return 0
+}
+
+load_lib gdb-python.exp
+
+set test "py-autoloaded-pretty-printers-in-newobjfile-event"
+set srcfile_main "${test}-main.cc"
+set executable_main ${test}-test
+set binfile_main [standard_output_file ${executable_main}]
+set srcfile_lib "${test}-lib.cc"
+set libname "lib${test}"
+set pyscriptfile_lib "${libname}.so-gdb.py"
+set binfile_lib [standard_output_file ${libname}.so]
+
+
+# Start with a fresh gdb.
+gdb_exit
+gdb_start
+
+# Skip all tests if Python scripting is not enabled.
+if { [skip_python_tests] } { continue }
+
+if {[gdb_compile_shlib ${srcdir}/${subdir}/${srcfile_lib} ${binfile_lib} \
+                       [list debug c++ -Wl,-soname,${libname}.so]] != ""} {
+    return -1
+}
+
+if {[gdb_compile "${srcdir}/${subdir}/${srcfile_main}" "${binfile_main}.o" \
+                 object [list debug c++]] != ""} {
+    return -1
+}
+
+set testobjdir [standard_output_file {}]
+if {[gdb_compile "${binfile_main}.o" "${binfile_main}" executable \
+                 [list debug "additional_flags=-L$testobjdir -l${test} \
+                              -Wl,-rpath=$testobjdir"]] != ""} {
+    return -1
+}
+
+# Start with a fresh gdb.
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+
+# Make the -gdb.py script available to gdb, it is automatically loaded by
+# gdb if it is put in the same directory as the library.
+set remote_python_file_autoload [gdb_remote_download host \
+                            ${srcdir}/${subdir}/${pyscriptfile_lib}]
+
+gdb_test_no_output "set auto-load safe-path ${remote_python_file_autoload}" \
+                   "set auto-load safe-path"
+
+# load the python file that defines a handler for the new_objfile event,
+# which will generate the output to check later
+# (prints information on available pretty-printers for objfile)
+set remote_python_file [gdb_remote_download host \
+                            ${srcdir}/${subdir}/${test}.py]
+gdb_test_no_output "source ${remote_python_file}" "load python file"
+
+gdb_load ${binfile_main}
+
+gdb_test_no_output "set print pretty on"
+
+gdb_breakpoint [gdb_get_line_number "break to inspect" ${srcfile_main}]
+
+# check that the handler prints output when test library is loaded
+# and that the pretty printer from autoloaded python file has been registered
+gdb_test "run" "new_objfile event for test library.*
+.*number of pretty printers: 1.*
+.*name of the first pretty printer: my_library.*"
+
+# check that pretty printer actually works
+gdb_test "print test" " .*MyClassTestLib object, id: 1.*"
+
+gdb_continue_to_end
diff --git a/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.py b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.py
new file mode 100644
index 00000000000..924f304fd33
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-autoloaded-pretty-printers-in-newobjfile-event.py
@@ -0,0 +1,34 @@ 
+# Copyright (C) 2021 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/>.
+
+# This file is part of the GDB testsuite. It tests that python pretty
+# printers defined in a python script that is autoloaded have been
+# registered when a custom event handler for the new_objfile event
+# is called.
+
+import gdb
+import os
+
+
+def new_objfile_handler(event):
+    assert(isinstance(event, gdb.NewObjFileEvent))
+    # only observe the custom test library
+    if os.path.basename(event.new_objfile.filename).find("libpy-autoloaded-pretty-printers-in-newobjfile-event") == 0:
+        print("new_objfile event for test library")
+        assert(len(event.new_objfile.pretty_printers) == 1)
+        print("number of pretty printers: {}".format(len(event.new_objfile.pretty_printers)))
+        print("name of the first pretty printer: {}".format(event.new_objfile.pretty_printers[0].name))
+
+gdb.events.new_objfile.connect(new_objfile_handler)