[lldb-dev] How to redirect stdin/out/err to different pty?

Sun Mar 23 11:31:37 PDT 2014

I am sorry, but nothing obvious comes to me right now, probably you'll need
to wait for Monday, when people more familiar with lldb will be able to
help you debug this problem.

2014-03-23 16:07 GMT+01:00 Eran Ifrah <eran.ifrah at gmail.com>:

>
>
>
> On Sun, Mar 23, 2014 at 4:29 PM, Piotr Rak <piotr.rak at gmail.com> wrote:
>
>> Sorry I misinformed you about posix_spawn - it is not true for Linux and
>> FreeBSD at least, it will use ordinary fork.
>>
>>
>> 2014-03-23 15:23 GMT+01:00 Piotr Rak <piotr.rak at gmail.com>:
>>
>>
>>> Hi,
>>>
>>> 2014-03-23 14:04 GMT+01:00 Eran Ifrah <eran.ifrah at gmail.com>:
>>>
>>> Thanks for your pointer Piotr. Here is the code I am using to open a
>>>> pseudo-terminal (there is the UI part, which I left out):
>>>>
>>>>     char __name[128];
>>>>     memset(__name, 0, sizeof(__name));
>>>>
>>>>     int master(-1);
>>>>     m_slave = -1;
>>>>     if(openpty(&master, &m_slave, __name, NULL, NULL) != 0)
>>>>         return wxT("");
>>>>
>>>>     // disable ECHO
>>>>     struct termios termio;
>>>>     tcgetattr(master, &termio);
>>>>     termio.c_lflag = ICANON;
>>>>     termio.c_oflag = ONOCR | ONLRET;
>>>>     tcsetattr(master, TCSANOW, &termio);
>>>>
>>>>     m_tty = wxString(__name, wxConvUTF8);
>>>>
>>>> At the end, m_tty contains a string name (e.g. /dev/pts/19 ).
>>>> Note that the above code works flawlessly when using it with gdb (i.e. if
>>>> I pass this "/dev/pts/19" to gdb's switch -tty=/dev/pts/19 I will get
>>>> all the inferior output/err/input to my internal terminal)
>>>>
>>>> However, doing the same with LLDB (using C++ API not the command line ,
>>>> i.e. passing "/dev/pts/19" as an argument to SBTarget::Launch(...)) I get
>>>> nothing as output...
>>>>
>>>> Looks sane to me.
>>>
>>>
>>>> Also, I am not sure I am following the idea behind replacing the
>>>> "Launch" function with my own fork(), looking at the code of Launch()
>>>> suggests that it does more than a simple fork...
>>>>
>>>>
>>> That was my idea to debug issue if nothing else helps.
>>> Or rather bisect on which side it really is, sorry if I did not make it
>>> clear...
>>> So I was trying suggest replacing SBTarget::Launch with fork,  write to
>>> child stdout/err, and see if that works alone....
>>>
>>> SBTarget::Launch is usually actually posix_spawn right now, it uses
>>> posix_spawnattr_addopen to open descriptors for your specified paths, and
>>> should open it 3 times - given current implementation - even it is just one
>>> file.
>>>
>>> Have you inspected SBProcess and SBError returned by SBTarget::Launch?
>>>
>>> I checked IsValid() on both and its OK for both. I can actually run
> "next" Continue etc and seems to be working. Its just that I can't seem to
> redirect the stdout/err to my own console.
>
>
>  Do you see your inferior process is indeed launching, just not
>>> displaying anything?
>>>
>> Yes, ps -ef shows the debugee
>
>>
>>>  Do you have an option to check if those terminals are actually being
>>> opened (like examining /proc/<pid>/fd for linux)?
>>>
>> The terminal is opened. Like I mentioned in my previous email, using the
> _same_ code with gdb works
> I also have a standalone terminal application which I wrote which is also
> using the same set of classes all of the are working for couple of years
> now without any problems
>
> I also tried this:
> I typed in my konsole 'tty' and used that as the input for Launch - it
> also seems to have no effect
>
>
>
>>> Good luck,
>>> /Piotr
>>>
>>> Any more hints?
>>>> Eran
>>>>
>>>>
>>>>
>>>> On Sat, Mar 22, 2014 at 9:36 PM, Piotr Rak <piotr.rak at gmail.com> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> It should.
>>>>> Have you opened master pseudoterminal like?:
>>>>>
>>>>>  int fd = posix_openpt(flags); // open("/dev/ptmx") might work here
>>>>> too but less portable;
>>>>> grantpt(fd);
>>>>> unlockpt(fd);
>>>>>
>>>>> Depending on target you might need some bizarre ioctls here, but
>>>>> assuming you are using Linux/FreeBSD/MacOSX
>>>>> you should be fine.
>>>>>
>>>>> If you had already master pseudo-terminal file descriptor you can skip
>>>>> steps above.
>>>>>
>>>>> You can use ptsname for master file descriptor it will return you name
>>>>> of slave pseudo-terminal for your master.
>>>>> Later you can pass name returned by ptsname(fd) as Launch arguments.
>>>>>
>>>>> If above won't work you can try replacing Launch() call with ordinary
>>>>> fork, and in child process:
>>>>>
>>>>> slavefd = open(slavename, O_RDWR);
>>>>>
>>>>> dup2(0, slavefd);
>>>>> dup2(1, slavefd);
>>>>> dup2(2, slavefd);
>>>>>
>>>>> And see if that works alone for you...
>>>>>
>>>>> Good luck,
>>>>> /Piotr
>>>>>
>>>>>
>>>>> 2014-03-22 19:29 GMT+01:00 Eran Ifrah <eran.ifrah at gmail.com>:
>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> I am trying to use the C++ API with good success so far.
>>>>>> I am now at a point where I want to redirect stdin/out/err of the
>>>>>> inferior to my application (my application creates a separate pseudo
>>>>>> terminal window)
>>>>>>
>>>>>> Looking at the SBTarget::Launch, I thought that simply passing
>>>>>> "/dev/pts/<some-number>" as the 3rd, 4th and 5th argument will do the trick
>>>>>> .. well, it did not.
>>>>>> I am missing something basic here, can anyone shed some light please?
>>>>>> or give an example (better) of how to achieve this?
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>> --
>>>>>> Eran Ifrah
>>>>>> Author of codelite, a cross platform open source C/C++ IDE:
>>>>>> http://www.codelite.org
>>>>>> wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>>>>>>
>>>>>> _______________________________________________
>>>>>> lldb-dev mailing list
>>>>>> lldb-dev at cs.uiuc.edu
>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Eran Ifrah
>>>> Author of codelite, a cross platform open source C/C++ IDE:
>>>> http://www.codelite.org
>>>> wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>>>>
>>>
>>>
>>
>
>
> --
> Eran Ifrah
> Author of codelite, a cross platform open source C/C++ IDE:
> http://www.codelite.org
> wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/lldb-dev/attachments/20140323/c554ca69/attachment.html>