[lldb-dev] How to redirect stdin/out/err to different pty?
Piotr Rak
piotr.rak at gmail.com
Wed Mar 26 14:09:20 PDT 2014
Sorry, we do have O_CREAT and even when open failed we'd exit with
different exit code earlier.
I'll rather go sleep - enough for today. :)
2014-03-26 22:01 GMT+01:00 Piotr Rak <piotr.rak at gmail.com>:
> Also other option is that we don't have O_CREAT in flags and we get ENOENT
> from open().... but again can not check that today.
>
>
> 2014-03-26 21:52 GMT+01:00 Piotr Rak <piotr.rak at gmail.com>:
>
> No, closing before dup2 is not required, it should close fd and it should
>> be also atomic. I am wondering now if LLDB sets FileActions like it was
>> expecting that we use posix_spawn.
>>
>> I can not check it today... but will look at it tomorrow or during
>> weekend.
>>
>>
>> 2014-03-26 21:33 GMT+01:00 Greg Clayton <gclayton at apple.com>:
>>
>> Looks like you might need to look at:
>>>
>>> ProcessMonitor::Launch(LaunchArgs *args)
>>>
>>> It is what does the fork + exec.
>>>
>>> It also looks like no matter what is sent to
>>> ProcessMonitor::Launch(LaunchArgs *args) for stdin, stdout, stderr, Linux
>>> _always_ launches using a pseudo terminal by doing:
>>>
>>> lldb_utility::PseudoTerminal terminal;
>>> if ((pid = terminal.Fork(err_str, err_len)) == -1)
>>>
>>>
>>> If you look at the "terminal.Fork()" code you will see that it actually
>>> sets stdin/out/err to the slave slide of the pseudo terminal, so there is
>>> no telling if the code in ProcessMonitor::Launch():
>>>
>>> if (stdin_path != NULL && stdin_path[0])
>>> if (!DupDescriptor(stdin_path, STDIN_FILENO, O_RDONLY))
>>> exit(eDupStdinFailed);
>>>
>>> if (stdout_path != NULL && stdout_path[0])
>>> if (!DupDescriptor(stdout_path, STDOUT_FILENO, O_WRONLY |
>>> O_CREAT))
>>> exit(eDupStdoutFailed);
>>>
>>> if (stderr_path != NULL && stderr_path[0])
>>> if (!DupDescriptor(stderr_path, STDERR_FILENO, O_WRONLY |
>>> O_CREAT))
>>> exit(eDupStderrFailed);
>>>
>>>
>>> Will work? ProcessMonitor::DupDescriptor() does:
>>>
>>>
>>> bool
>>> ProcessMonitor::DupDescriptor(const char *path, int fd, int flags)
>>> {
>>> int target_fd = open(path, flags, 0666);
>>>
>>> if (target_fd == -1)
>>> return false;
>>>
>>> return (dup2(target_fd, fd) == -1) ? false : true;
>>> }
>>>
>>> I would assume you would need to call close() on stdin/out/err first?
>>> Again the PseudoTerminal::Fork() has always already setup stdin/out/err to
>>> the slave side and the DupDescriptor calls are probably failing.
>>>
>>> Greg
>>>
>>>
>>> On Mar 26, 2014, at 12:26 PM, Piotr Rak <piotr.rak at gmail.com> wrote:
>>>
>>> > Hi,
>>> >
>>> > That got me curious and now I am bit confused how it works, and it
>>> should be really simple.
>>> >
>>> > I've checked Greg's example, it will just exit before main doing
>>> nothing.
>>> > I've no idea why yet, however I attached my perfect tracee:
>>> >
>>> > extern "C" void _start()
>>> > {
>>> > __asm__ volatile (
>>> > "again:;"
>>> > "int $0x03;"
>>> > "jmp again;"
>>> > "movl $1,%eax;"
>>> > "xorl %ebx, %ebx;"
>>> > "int $0x80;"
>>> > );
>>> > }
>>> > ls -al /proc/`pidof hello`/fd
>>> >
>>> > lrwx------ 1 prak prak 64 03-26 19:42 0 -> /dev/pts/19
>>> > lrwx------ 1 prak prak 64 03-26 19:42 1 -> /dev/pts/19
>>> > lrwx------ 1 prak prak 64 03-26 19:42 2 -> /dev/pts/19
>>> > lrwx------ 1 prak prak 64 03-26 19:42 3 -> /dev/ptmx
>>> > lrwx------ 1 prak prak 64 03-26 19:42 5 -> /dev/pts/19
>>> >
>>> > ls -al /proc/`pidof lldb`/fd
>>> >
>>> > lrwx------ 1 prak prak 64 03-26 19:43 0 -> /dev/pts/16
>>> > lrwx------ 1 prak prak 64 03-26 19:43 1 -> /dev/pts/16
>>> > lrwx------ 1 prak prak 64 03-26 19:43 2 -> /dev/pts/16
>>> > lrwx------ 1 prak prak 64 03-26 19:43 3 -> /dev/ptmx
>>> > lrwx------ 1 prak prak 64 03-26 19:43 4 -> /dev/ptmx
>>> > lr-x------ 1 prak prak 64 03-26 19:43 5 -> pipe:[1301667]
>>> > l-wx------ 1 prak prak 64 03-26 19:43 6 -> pipe:[1301667]
>>> > lr-x------ 1 prak prak 64 03-26 19:43 7 -> pipe:[1299830]
>>> > l-wx------ 1 prak prak 64 03-26 19:43 8 -> pipe:[1299830]
>>> >
>>> > So it was spawned as usual using fork() by Linux/ProcessMonitor.cpp
>>> > And it was given slave pts, lldb however has no '/tmp/out.txt' file
>>> anywhere.
>>> >
>>> > Should this for this case?:
>>> > a) be passed opened to inferior before exec, or
>>> > b) lldb should read master pty and write to /tmp/out.txt
>>> >
>>> > I would guess that should be a:
>>> >
>>> > But probably then:
>>> >
>>> > SetSTDIOFileDescriptor(m_monitor->GetTerminalFD());
>>> >
>>> > from ProcessPosix::DoLaunch() ProcessPosix.cpp:253 after creating
>>> process spoils the fun.
>>> > Also std{in,err,path)_path had to be empty here.
>>> >
>>> > Cheers,
>>> > /Piotr
>>> >
>>> >
>>> > 2014-03-26 19:08 GMT+01:00 Greg Clayton <gclayton at apple.com>:
>>> > 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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