225 lines
7.9 KiB
Diff
225 lines
7.9 KiB
Diff
From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
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From: Keith Seitz <keiths@redhat.com>
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Date: Thu, 4 Jun 2020 17:16:48 -0700
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Subject: gdb-rhbz1829702-fix-python39.patch
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;; Backport "Fix Python 3.9 related runtime problems"
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;; Kevin Buettner <kevinb@redhat.com> and Keith Seitz <keiths@redhat.com>
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commit c47bae859a5af0d95224d90000df0e529f7c5aa0
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Author: Kevin Buettner <kevinb@redhat.com>
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Date: Wed May 27 20:05:40 2020 -0700
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Fix Python3.9 related runtime problems
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Python3.9b1 is now available on Rawhide. GDB w/ Python 3.9 support
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can be built using the configure switch -with-python=/usr/bin/python3.9.
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Attempting to run gdb/Python3.9 segfaults on startup:
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#0 0x00007ffff7b0582c in PyEval_ReleaseLock () from /lib64/libpython3.9
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.so.1.0
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#1 0x000000000069ccbf in do_start_initialization ()
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at worktree-test1/gdb/python/python.c:1789
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#2 _initialize_python ()
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at worktree-test1/gdb/python/python.c:1877
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#3 0x00000000007afb0a in initialize_all_files () at init.c:237
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...
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Consulting the the documentation...
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https://docs.python.org/3/c-api/init.html
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...we find that PyEval_ReleaseLock() has been deprecated since version
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3.2. It recommends using PyEval_SaveThread or PyEval_ReleaseThread()
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instead. In do_start_initialization, in gdb/python/python.c, we
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can replace the calls to PyThreadState_Swap() and PyEval_ReleaseLock()
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with a single call to PyEval_SaveThread. (Thanks to Keith Seitz
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for working this out.)
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With that in place, GDB gets a little bit further. It still dies
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on startup, but the backtrace is different:
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#0 0x00007ffff7b04306 in PyOS_InterruptOccurred ()
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from /lib64/libpython3.9.so.1.0
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#1 0x0000000000576e86 in check_quit_flag ()
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at worktree-test1/gdb/extension.c:776
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#2 0x0000000000576f8a in set_active_ext_lang (now_active=now_active@entry=0x983c00 <extension_language_python>)
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at worktree-test1/gdb/extension.c:705
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#3 0x000000000069d399 in gdbpy_enter::gdbpy_enter (this=0x7fffffffd2d0,
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gdbarch=0x0, language=0x0)
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at worktree-test1/gdb/python/python.c:211
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#4 0x0000000000686e00 in python_new_inferior (inf=0xddeb10)
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at worktree-test1/gdb/python/py-inferior.c:251
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#5 0x00000000005d9fb9 in std::function<void (inferior*)>::operator()(inferior*) const (__args#0=<optimized out>, this=0xccad20)
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at /usr/include/c++/10/bits/std_function.h:617
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#6 gdb::observers::observable<inferior*>::notify (args#0=0xddeb10,
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this=<optimized out>)
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at worktree-test1/gdb/../gdbsupport/observable.h:106
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#7 add_inferior_silent (pid=0)
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at worktree-test1/gdb/inferior.c:113
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#8 0x00000000005dbcb8 in initialize_inferiors ()
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at worktree-test1/gdb/inferior.c:947
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...
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We checked with some Python Developers and were told that we should
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acquire the GIL prior to calling any Python C API function. We
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definitely don't have the GIL for calls of PyOS_InterruptOccurred().
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I moved class_gdbpy_gil earlier in the file and use it in
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gdbpy_check_quit_flag() to acquire (and automatically release) the
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GIL.
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With those changes in place, I was able to run to a GDB prompt. But,
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when trying to quit, it segfaulted again due to due to some other
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problems with gdbpy_check_quit_flag():
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Thread 1 "gdb" received signal SIGSEGV, Segmentation fault.
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0x00007ffff7bbab0c in new_threadstate () from /lib64/libpython3.9.so.1.0
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(top-gdb) bt 8
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#0 0x00007ffff7bbab0c in new_threadstate () from /lib64/libpython3.9.so.1.0
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#1 0x00007ffff7afa5ea in PyGILState_Ensure.cold ()
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from /lib64/libpython3.9.so.1.0
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#2 0x000000000069b58c in gdbpy_gil::gdbpy_gil (this=<synthetic pointer>)
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at worktree-test1/gdb/python/python.c:278
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#3 gdbpy_check_quit_flag (extlang=<optimized out>)
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at worktree-test1/gdb/python/python.c:278
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#4 0x0000000000576e96 in check_quit_flag ()
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at worktree-test1/gdb/extension.c:776
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#5 0x000000000057700c in restore_active_ext_lang (previous=0xe9c050)
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at worktree-test1/gdb/extension.c:729
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#6 0x000000000088913a in do_my_cleanups (
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pmy_chain=0xc31870 <final_cleanup_chain>,
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old_chain=0xae5720 <sentinel_cleanup>)
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at worktree-test1/gdbsupport/cleanups.cc:131
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#7 do_final_cleanups ()
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at worktree-test1/gdbsupport/cleanups.cc:143
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In this case, we're trying to call a Python C API function after
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Py_Finalize() has been called from finalize_python(). I made
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finalize_python set gdb_python_initialized to false and then cause
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check_quit_flag() to return early when it's false.
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With these changes in place, GDB seems to be working again with
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Python3.9b1. I think it likely that there are other problems lurking.
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I wouldn't be surprised to find that there are other calls into Python
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where we don't first make sure that we have the GIL. Further changes
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may well be needed.
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I see no regressions testing on Rawhide using a GDB built with the
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default Python version (3.8.3) versus one built using Python 3.9b1.
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I've also tested on Fedora 28, 29, 30, 31, and 32 (all x86_64) using
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the default (though updated) system installed versions of Python on
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those OSes. This means that I've tested against Python versions
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2.7.15, 2.7.17, 2.7.18, 3.7.7, 3.8.2, and 3.8.3. In each case GDB
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still builds without problem and shows no regressions after applying
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this patch.
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gdb/ChangeLog:
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2020-MM-DD Kevin Buettner <kevinb@redhat.com>
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Keith Seitz <keiths@redhat.com>
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* python/python.c (do_start_initialization): For Python 3.9 and
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later, call PyEval_SaveThread instead of PyEval_ReleaseLock.
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(class gdbpy_gil): Move to earlier in file.
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(finalize_python): Set gdb_python_initialized.
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(gdbpy_check_quit_flag): Acquire GIL via gdbpy_gil. Return early
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when not initialized.
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diff --git a/gdb/python/python.c b/gdb/python/python.c
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--- a/gdb/python/python.c
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+++ b/gdb/python/python.c
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@@ -234,6 +234,30 @@ gdbpy_enter::~gdbpy_enter ()
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PyGILState_Release (m_state);
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}
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+/* A helper class to save and restore the GIL, but without touching
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+ the other globals that are handled by gdbpy_enter. */
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+
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+class gdbpy_gil
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+{
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+public:
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+
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+ gdbpy_gil ()
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+ : m_state (PyGILState_Ensure ())
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+ {
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+ }
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+
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+ ~gdbpy_gil ()
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+ {
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+ PyGILState_Release (m_state);
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+ }
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+
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+ DISABLE_COPY_AND_ASSIGN (gdbpy_gil);
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+
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+private:
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+
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+ PyGILState_STATE m_state;
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+};
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+
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/* Set the quit flag. */
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static void
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@@ -247,6 +271,10 @@ gdbpy_set_quit_flag (const struct extension_language_defn *extlang)
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static int
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gdbpy_check_quit_flag (const struct extension_language_defn *extlang)
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{
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+ if (!gdb_python_initialized)
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+ return 0;
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+
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+ gdbpy_gil gil;
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return PyOS_InterruptOccurred ();
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}
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@@ -924,30 +952,6 @@ gdbpy_source_script (const struct extension_language_defn *extlang,
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/* Posting and handling events. */
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-/* A helper class to save and restore the GIL, but without touching
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- the other globals that are handled by gdbpy_enter. */
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-
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-class gdbpy_gil
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-{
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-public:
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-
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- gdbpy_gil ()
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- : m_state (PyGILState_Ensure ())
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- {
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- }
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-
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- ~gdbpy_gil ()
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- {
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- PyGILState_Release (m_state);
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- }
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-
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- DISABLE_COPY_AND_ASSIGN (gdbpy_gil);
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-
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-private:
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-
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- PyGILState_STATE m_state;
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-};
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-
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/* A single event. */
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struct gdbpy_event
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{
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@@ -1548,6 +1552,7 @@ finalize_python (void *ignore)
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Py_Finalize ();
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+ gdb_python_initialized = false;
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restore_active_ext_lang (previous_active);
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}
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@@ -1720,8 +1725,7 @@ do_start_initialization ()
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return false;
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/* Release the GIL while gdb runs. */
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- PyThreadState_Swap (NULL);
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- PyEval_ReleaseLock ();
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+ PyEval_SaveThread ();
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make_final_cleanup (finalize_python, NULL);
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