[lldb-dev] Weird stop stack while hitting breakpoint

Fri Mar 18 16:34:43 PDT 2016

You iterate over all the threads and ask each thread what its stop reason is.

> On Mar 18, 2016, at 4:25 PM, Jeffrey Tan via lldb-dev <lldb-dev at lists.llvm.org> wrote:
> 
> 
> Hmm, interesting, I got the stop reason from the lldb.SBProcess.GetProcessFromEvent(event).GetSelectedThread().GetStopReason(). Is that thread not the one that stopped? But you are right, the breakpoint hits in another thread:
> 
> thread #87: tid = 1006769, 0x000000000042eacd biggrep_master_server_async`facebook::biggrep::BigGrepMasterAsync::future_find(this=0x00007f3ea2d74fd0, corpus=error: summary string parsing error, needle=error: summary string parsing error, options=0x00007f3e899fc7e0) + 51 at BigGrepMasterAsync.cpp:171, name = 'BigGrep-pri3-32', stop reason = breakpoint 1.1
> 
> How do I know which thread hits the breakpoint?
> 
> Jeffrey
> 
> 
> On Fri, Mar 18, 2016 at 4:12 PM, Jim Ingham <jingham at apple.com> wrote:
> You only show one thread in your example.  Did another thread have a valid stop reason?  lldb shouldn’t be stopping for no reason anywhere…
> 
> Jim
> 
>> On Mar 18, 2016, at 4:08 PM, Jeffrey Tan via lldb-dev <lldb-dev at lists.llvm.org> wrote:
>> 
>> Btw: the breakpoint I set is:
>> "b BigGrepMasterAsync.cpp:171" which is not in any of the stopped stack frames.
>> 
>> On Fri, Mar 18, 2016 at 3:47 PM, Jeffrey Tan <jeffrey.fudan at gmail.com> wrote:
>> Hi,
>> 
>> Our IDE(wrapping lldb using python) works fine on Linux for simple hello world cases. While trying a real world case, I found whenever we set a source line breakpoint, then trigger the code path, lldb will send a stopped state process event, with thread.GetStopReason() being None and with weird callstack. Any ideas why do I get this stop stack(code is listed at the end)? I have verified that if I do not set breakpoint and trigger the same code path does not cause this stop event to generate.
>> 
>> bt
>> * thread #1: tid = 952490, 0x00007fd7cb2daa83 libc.so.6`__GI_epoll_wait + 51, name = 'biggrep_master_'
>>   * frame #0: 0x00007fd7cb2daa83 libc.so.6`__GI_epoll_wait + 51
>>     frame #1: 0x000000000271189f biggrep_master_server_async`epoll_dispatch(base=0x00007fd7ca970800, arg=0x00007fd7ca62c1e0, tv=<unavailable>) + 127 at epoll.c:315
>>     frame #2: 0x000000000270f6d1 biggrep_master_server_async`event_base_loop(base=0x00007fd7ca970800, flags=<unavailable>) + 225 at event.c:524
>>     frame #3: 0x00000000025f9378 biggrep_master_server_async`folly::EventBase::loopBody(this=0x00007fd7ca945180, flags=0) + 834 at EventBase.cpp:335
>>     frame #4: 0x00000000025f900b biggrep_master_server_async`folly::EventBase::loop(this=0x00007fd7ca945180) + 29 at EventBase.cpp:287
>>     frame #5: 0x00000000025fa053 biggrep_master_server_async`folly::EventBase::loopForever(this=0x00007fd7ca945180) + 109 at EventBase.cpp:435
>>     frame #6: 0x0000000001e24b72 biggrep_master_server_async`apache::thrift::ThriftServer::serve(this=0x00007fd7ca96d710) + 110 at ThriftServer.cpp:365
>>     frame #7: 0x00000000004906bc biggrep_master_server_async`facebook::services::ServiceFramework::startFramework(this=0x00007ffc06776140, waitUntilStop=true) + 1942 at ServiceFramework.cpp:885
>>     frame #8: 0x000000000048fe6d biggrep_master_server_async`facebook::services::ServiceFramework::go(this=0x00007ffc06776140, waitUntilStop=true) + 35 at ServiceFramework.cpp:775
>>     frame #9: 0x00000000004219a7 biggrep_master_server_async`main(argc=1, argv=0x00007ffc067769d8) + 2306 at BigGrepMasterServerAsync.cpp:134
>>     frame #10: 0x00007fd7cb1ed0f6 libc.so.6`__libc_start_main + 246
>>     frame #11: 0x0000000000420bfc biggrep_master_server_async`_start + 41 at start.S:122
>> 
>> Here is the code snippet of handling code:
>> def _handle_process_event(self, event):
>>         # Ignore non-stopping events.
>>         if lldb.SBProcess.GetRestartedFromEvent(event):
>>             log_debug('Non stopping event: %s' % str(event))
>>             return
>> 
>>         process = lldb.SBProcess.GetProcessFromEvent(event)
>>         if process.state == lldb.eStateStopped:
>>             self._send_paused_notification(process)
>>         elif process.state == lldb.eStateExited:
>>             exit_message = 'Process(%d) exited with: %u' % (
>>                     process.GetProcessID(),
>>                     process.GetExitStatus())
>>             if process.GetExitDescription():
>>                 exit_message += (', ' + process.GetExitDescription())
>>             self._send_user_output('log', exit_message)
>>             self.should_quit = True
>>         else:
>>             self._send_notification('Debugger.resumed', None)
>> 
>>         event_type = event.GetType()
>>         if event_type == lldb.SBProcess.eBroadcastBitSTDOUT:
>>             # Read stdout from inferior.
>>             process_output = ''
>>             while True:
>>                 output_part = process.GetSTDOUT(1024)
>>                 if not output_part or len(output_part) == 0:
>>                     break
>>                 process_output += output_part
>>             self._send_user_output('log', process_output)
>> 
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