[lldb-dev] How to redirect stdin/out/err to different pty?
Greg Clayton
gclayton at apple.com
Wed Mar 26 11:08:46 PDT 2014
Seems like we are having some problem re-directing to terminals and files that exist. I would try debugging through the launch process and see who is doing what with file re-direction. It works on MacOSX just fine, so this is probably a linux only issue. Linux does fork() + exec() so some code in there isn't doing the right things.
% lldb
(lldb) settings set target.output-path /tmp/out.txt
(lldb) file /bin/ls
Current executable set to '/bin/ls' (x86_64).
(lldb) run /tmp/
(lldb) Process 65933 launched: '/bin/ls' (x86_64)
Process 65933 exited with status = 0 (0x00000000)
(lldb) q
% cat /tmp/out.txt
launch-B6FwKk
launch-OEyacj
launchd-142.5fRyOk
launchd-175.RBU3HO
launchd-193.Asuh1k
launchd-2701.dSHLJu
launchd-738.U2ACnW
out.txt
% xcrun lldb
(lldb) settings set target.output-path /tmp/out.txt
(lldb) file /bin/ls
Current executable set to '/bin/ls' (x86_64).
(lldb) run /
(lldb) Process 65940 launched: '/bin/ls' (x86_64)
Process 65940 exited with status = 0 (0x00000000)
(lldb) q
lldb:/tmp % cat /tmp/out.txt
AppleInternal
Applications
Library
Network
SWE
System
Users
Volumes
bin
cores
dev
etc
home
mach_kernel
net
So this works on Darwin and needs to be fixed on Linux.
Greg
On Mar 25, 2014, at 7:15 AM, Eran Ifrah <eran.ifrah at gmail.com> wrote:
> Hello Greg,
> Thanks for the input. It still does not work ( I rewrote my terminal code to look similar to lldb's PseudoTerminal, and it is still not working)
>
> To simplify things, I tried some basic things with the command line tool 'lldb':
>
> I created a file ~/.lldbinit with the following content:
>
> eran at eran-linux: ~/llvm/build/bin $ cat ~/.lldbinit
> settings set target.output-path /tmp/dbg.out
> eran at eran-linux: ~/llvm/build/bin $
>
> I then ran lldb while having tail -f /tmp/dbg.out& in another terminal to see if the stdout is being redirected
>
> Now, this is the interesting part:
> In the first run when the file /tmp/dbg.out was empty - the redirection worked (tail showed the debuggee stdout)
> In the second run (and later) - nothing was written to the file
>
> However, if I truncate the file using the below command:
>
> $ > /tmp/dbg.out
>
> and run lldb again - I see the stdout again - but same as before only for the first time (i.e. as long as the file is empty the stdout was redirected)
>
> The next thing I tried was to use a terminal name for redirection:
>
> - Open a new terminal and type `tty` (in my case it gave /dev/pts/19 )
> - Edit the ~/.lldbinit: settings set target.output-path /dev/pts/19
> - Start lldb and verify that the setting is set properly by running: settings show target.output-path
> - Run the program under lldb - the output is not redirected (i.e. it is show in the same console where I ran lldb)
>
> Any ideas?
>
> P.S.
> Sorry if this looks like a voodoo, but this is what I am getting here... ;)
>
> Eran
>
>
>
>
>
> On Mon, Mar 24, 2014 at 6:46 PM, Greg Clayton <gclayton at apple.com> wrote:
> Check out the PseudoTerminal class in trunk/source/Utility/PseudoTerminal.cpp.
>
> See the function named PseudoTerminal::OpenFirstAvailableMaster(...). You must call posix_openpt, grantpt, and unlockpt. I am guessing that because you aren't calling grantpt and granting access to the slave you are failing to be able to use the slave in your child process.
>
> Greg Clayton
>
> On Mar 23, 2014, at 11:32 AM, Eran Ifrah <eran.ifrah at gmail.com> wrote:
>
> > Sure, thanks for the help so far
> > Eran
> >
> >
> > On Sun, Mar 23, 2014 at 8:31 PM, Piotr Rak <piotr.rak at gmail.com> wrote:
> > 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
> >
> >
> >
> >
> > --
> > 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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