[lldb-dev] Weird stop stack while hitting breakpoint

[Jeffrey Tan via lldb-dev]

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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