From 2c473def12b08100e6b56261f01112db7f6aeab5 Mon Sep 17 00:00:00 2001 From: Michael Weghorn Date: Tue, 27 Apr 2021 10:02:42 -0400 Subject: gdb: do autoload before notifying Python side in new_objfile event 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. Change-Id: I8275b3f4c3bec32e56dd7892f9a59d89544edf89 --- gdb/python/py-inferior.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'gdb/python/py-inferior.c') diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c index c2861cc..febd2a7 100644 --- a/gdb/python/py-inferior.c +++ b/gdb/python/py-inferior.c @@ -18,6 +18,7 @@ along with this program. If not, see . */ #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"); -- cgit v1.1