Hi,
I have been spending long time troubleshooting a race condition in our lldb
python test. I finally narrowed down to one code change that caused the
race: basically, whenever I store SBTarget in DebuggerTestCase's
self.target field lldb will randomly crash during destruction(see below).
In the code, if I modify the two "self.target" to local variable "target"
the random crash will disappear.
I am not a python expert. Why is holding SBTarget will cause the test to
random crash? Do I have to set every SBXXX fields to None before
calling SBDebugger.Destroy()?
==========================Crash Stack==========================
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000010
VM Regions Near 0x10:
-->
__TEXT 000000010d145000-000000010d146000 [ 4K]
r-x/rwx SM=COW
/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 com.apple.LLDB.framework 0x00000001101c037d
lldb_private::Listener::BroadcasterWillDestruct(lldb_private::Broadcaster*)
+ 95
1 com.apple.LLDB.framework 0x00000001101a0da2
lldb_private::Broadcaster::Clear() + 50
2 com.apple.LLDB.framework 0x00000001101a0ced
lldb_private::Broadcaster::~Broadcaster() + 75
3 com.apple.LLDB.framework 0x00000001103d6879
lldb_private::Target::~Target() + 741
4 com.apple.LLDB.framework 0x00000001103d6c20
lldb_private::Target::~Target() + 14
5 libc++.1.dylib 0x00007fff896448a6
std::__1::__shared_weak_count::__release_shared() + 44
6 com.apple.LLDB.framework 0x000000010e560664
_wrap_delete_SBTarget(_object*, _object*) + 123
7 org.python.python 0x000000010d15a50a PyObject_Call + 99
==========================Code==========================
from find_lldb import lldb
from simplest_event_thread import LLDBListenerThread
import unittest
import threading
running_signal = threading.Event()
stopped_signal = threading.Event()
def launch_debugging(debugger, stop_at_entry):
error = lldb.SBError()
listener = lldb.SBListener('Chrome Dev Tools Listener')
target = debugger.GetSelectedTarget()
process = target.Launch (listener,
None, # argv
None, # envp
None, # stdin_path
None, # stdout_path
None, # stderr_path
None, # working directory
0, # launch flags
stop_at_entry, # Stop at entry
error) # error
print 'Launch result: %s' % str(error)
event_thread = LLDBListenerThread(debugger, running_signal,
stopped_signal)
event_thread.start()
running_signal.set()
return event_thread
class DebuggerTestCase:
def wait_for_process_stop(self):
running_signal.wait()
running_signal.clear()
stopped_signal.wait()
stopped_signal.clear()
def test_breakpoint_at_line(self):
debugger = lldb.SBDebugger.Create()
debugger.SetAsync(True)
executable_path =
'~/Personal/compiler/CompilerConstruction/code/compiler'
*self.target* =
debugger.CreateTargetWithFileAndArch(executable_path,
lldb.LLDB_ARCH_DEFAULT)
event_thread = launch_debugging(debugger, stop_at_entry=True)
process = debugger.GetSelectedTarget().process
self.wait_for_process_stop() # wait for entry breakpoint.
*self.target*.BreakpointCreateByName('main')
process.Continue()
self.wait_for_process_stop() # wait for main breakpoint.
event_thread.should_quit = True
event_thread.join()
lldb.SBDebugger.Destroy(debugger)
if __name__ == '__main__':
test = DebuggerTestCase()
for i in range(20):
test.test_breakpoint_at_line()
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