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

[Piotr Rak]

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?
>
> Do you see your inferior process is indeed launching, just not displaying
> anything?
>
> Do you have an option to check if those terminals are actually being
> opened (like examining /proc/<pid>/fd for linux)?
>
> 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
>>
>
>
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