apolyakov added inline comments.
================
Comment at: lit/tools/lldb-mi/target/inputs/target-select-so-path.py:8-11
+def get_free_port():
+ s = socket.socket()
+ s.bind(('', 0))
+ return s.getsockname()[1]
----------------
labath wrote:
> apolyakov wrote:
> > labath wrote:
> > > This is still racy, because the port can be snatched from under you
> > > between the time you get the free port and the time when lldb-server
> > > binds to it. If this was the only test doing it then it might be fine,
> > > but since this is going to be running concurrently with other tests, all
> > > of which are fetching free ports, the chances of that happening add up.
> > >
> > > (Also, binding to the wildcard address will trigger a firewall popup on
> > > some machines.)
> > There is a problem with getting port from lldb-server. If we run
> > `lldb-server gdbserver --pipe 0 ocalhost:0`, it'll print port number to its
> > stdout, but we can't get it using pipes since to do this we need to wait
> > until lldb-server finishes that isn't what we want.
> Aha, I see. lldb-server does not really expect you to pass std file
> descriptor as the --pipe argument. Normally you would create a separate fd
> and pass that instead. Doing that from python is a bit icky, but doable:
> ```
> (r, w) = os.pipe()
> kwargs = {}
> if sys.version_info >= (3,0):
> kwargs["pass_fds"] = [w]
> llgs = subprocess.Popen(["lldb-server", "gdbserver", "--pipe", str(w), ...],
> **kwargs)
> port_bytes = os.read(r, 10)
> port = int(port_bytes.decode("utf-8").strip('\x00'))
> ```
>
> Alternatively, we could modify lldb-server to print the port number to stdout
> in addition to any --pipe arguments (sounds like a good addition anyway, as
> it enables easy free port selection for a shell user), and then you can sniff
> that text from here.
`--pipe 0` prints port number exactly to stdout, so there will not be a
difference for us. It's not so simple to get port from lldb-server's stdout in
python, so I don't think it will save us.
https://reviews.llvm.org/D49739
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