[lldb-dev] LLDB Process Attach Failed When Waiting

Ryan Lovelett via lldb-dev lldb-dev at lists.llvm.org
Wed Jun 6 14:20:36 PDT 2018

Huzzah! I have a working proof of concept.

A few more questions (I hope I'm not wearing out my welcome):

1. There seems to be a "sleep" capability in the DNBProcessAttachWait method [1]. I'm not exactly sure how this "sleep" function works. When I use it the sleep seems to be a no-op. Is there another function that should be used for Linux?

2. DNBProcessAttachWait seems to have a timeout capability [2]. As far as I can tell, the argument timeout_abstime is hard-coded as NULL. Thus rendering that timer/timeout dead code.  Should replicate that in the Linux code as well?

3. Are there, or are there expected to be, tests for this stuff?

[1] https://github.com/llvm-mirror/lldb/blob/b64ab3f60c8faa43841af88b10dbcbfd073a82ea/tools/debugserver/source/DNB.cpp#L743
[2] https://github.com/llvm-mirror/lldb/blob/b64ab3f60c8faa43841af88b10dbcbfd073a82ea/tools/debugserver/source/DNB.cpp#L720-L729

On Wed, Jun 6, 2018, at 10:38 AM, Pavel Labath wrote:
> There are other options available as well, but for this particular
> scenario, I'd go with the following:
> - start debugging the client, set a breakpoint just before it sends
> the vAttach packet
> - when the client reaches this breakpoint, attach a debugger to the
> server (it will already be running at this point)
> - let the client send the packet
> - step through the server as it processes it
> That's if you want an interactive debug session. If you just want to
> see the logs, it should be sufficient to set LLDB_DEBUGSERVER_LOG_FILE
> and LLDB_SERVER_LOG_CHANNELS environment variables before starting
> lldb.
> On Wed, 6 Jun 2018 at 13:59, Ryan Lovelett <ryan at lovelett.me> wrote:
> >
> > Does anyone have any specific suggestions on how I might go about debugging/testing this? Specifically, turning on the logging in the gdb-server and also launching lldb-server separate from lldb so that I can actually attach a debugger to it.
> >
> > My workflow right now is to start the gdb-server like so:
> >
> > $ lldb-server gdb-server --log-file /tmp/gdb-server.txt *:1234
> >
> > Then connect the main lldb process like this:
> >
> > $ lldb
> > (lldb) platform select remote-gdb-server
> > (lldb) platform connect connect://localhost:1234
> This won't work. You are starting up a "gdb-server" instance of
> lldb-server and then connecting to it as if it was a platform
> instance. For "local" debugging you don't need that. You only need to
> mess with the platform when doing "true" remote debugging  That's
> probably why the latter attempt to attach fails with a weird error.

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