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# Copyright (C) 2024-2025 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/>.
import gdb
from gdb.unwinder import FrameId, Unwinder
# Cached FrameId. See set_break_bt_here_frame_id for details.
break_bt_here_frame_id = None
def set_break_bt_here_frame_id(pc, cfa):
"""Call this to pre-calculate the FrameId for the frame our unwinder
is going to claim, this avoids us having to actually figure out a
frame-id within the unwinder, something which is going to be hard
to do in a cross-target way.
Instead we first run the test without the Python unwinder in
place, use 'maint print frame-id' to record the frame-id, then,
after loading this Python script, we all this function to record
the frame-id that the unwinder should use."""
global break_bt_here_frame_id
break_bt_here_frame_id = FrameId(cfa, pc)
class break_unwinding(Unwinder):
"""An unwinder for the function 'break_bt_here'. This unwinder will
claim any frame for the function in question, but doesn't provide
any unwound register values. Importantly, we don't provide a
previous $pc value, this means that if we are stopped in
'break_bt_here' then we should fail to unwind beyond frame #0."""
def __init__(self):
Unwinder.__init__(self, "break unwinding")
def __call__(self, pending_frame):
pc_desc = pending_frame.architecture().registers().find("pc")
pc = pending_frame.read_register(pc_desc)
if pc.is_optimized_out:
return None
block = gdb.block_for_pc(pc)
if block == None:
return None
func = block.function
if func == None:
return None
if str(func) != "break_bt_here":
return None
global break_bt_here_frame_id
if break_bt_here_frame_id is None:
return None
return pending_frame.create_unwind_info(break_bt_here_frame_id)
gdb.unwinder.register_unwinder(None, break_unwinding(), True)
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