One more thing that can help prevent people from using `preexec_fn`.
Also adds conditional skips to two tests exposing ASAN flakiness on the Ubuntu 20.04 Address Sanitizer Github CI system. When that build is run on more modern systems the "problem" does not show up. It seems ASAN implementation related.
Co-authored-by: Zackery Spytz <zspytz@gmail.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Just in case there is ever an issue with _posixsubprocess's use of
vfork() due to the complexity of using it properly and potential
directions that Linux platforms where it defaults to on could take, this
adds a failsafe so that users can disable its use entirely by setting
a global flag.
No known reason to disable it exists. But it'd be a shame to encounter
one and not be able to use CPython without patching and rebuilding it.
See the linked issue for some discussion on reasoning.
Also documents the existing way to disable posix_spawn.
* Document os-system, subprocess Patch
* Update Doc/library/os.rst
Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
When the modern text= spelling of the universal_newlines= parameter was added
for Python 3.7, check_output's special case around input=None was overlooked.
So it behaved differently with universal_newlines=True vs text=True. This
reconciles the behavior to be consistent and adds a test to guarantee it.
Also clarifies the existing check_output documentation.
Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>
The issue being resolved is shown in the 3.10 docs (if you select docs for older versions you won't see a visual glitch).
The newer sphinx version that produces the 3.10 docs doesn't treat the backslash to escape things in some situations it previously did.
Added a note in the `subprocess` docs that recommend using `shlex.quote` without mentioning that this is only applicable to Unix.
Also added a warning straight into the `shlex` docs since it only says "for simple syntaxes resembling that of the Unix shell" and says using `quote` plugs the security hole without mentioning this important caveat.
Clarify in the subprocess documentation how searching for the executable to run works, noting that ``sys.executable`` is the recommended way to find the current interpreter.
* Add F_SETPIPE_SZ and F_GETPIPE_SZ to fcntl module
* Add pipesize parameter for subprocess.Popen class
This will allow the user to control the size of the pipes.
On linux the default is 64K. When a pipe is full it blocks for writing.
When a pipe is empty it blocks for reading. On processes that are
very fast this can lead to a lot of wasted CPU cycles. On a typical
Linux system the max pipe size is 1024K which is much better.
For high performance-oriented libraries such as xopen it is nice to
be able to set the pipe size.
The workaround without this feature is to use my_popen_process.stdout.fileno() in
conjuction with fcntl and 1031 (value of F_SETPIPE_SZ) to acquire this behavior.
On Unix, subprocess.Popen.send_signal() now polls the process status.
Polling reduces the risk of sending a signal to the wrong process if
the process completed, the Popen.returncode attribute is still None,
and the pid has been reassigned (recycled) to a new different
process.
* subprocess: Add user, group and extra_groups paremeters to subprocess.Popen
This adds a `user` parameter to the Popen constructor that will call
setreuid() in the child before calling exec(). This allows processes
running as root to safely drop privileges before running the subprocess
without having to use a preexec_fn.
This also adds a `group` parameter that will call setregid() in
the child process before calling exec().
Finally an `extra_groups` parameter was added that will call
setgroups() to set the supplimental groups.
Document that subprocess.Popen no longer raise an exception on error
like missing program on very specific platforms when using
os.posix_spawn() is used.
Clarify capturing or suppressing stdout and stderr on the old call APIs.
Do not state that they are equivalent to run() calls when they are not implemented using run as that was misleading. Unlike run they cannot handle stdout or stderr being set to PIPE without a risk of deadlock.
* universal_newlines defaulting to False would suggest, that not
specifying universal_newlines explicitly and setting text to True
should cause an error, which is not the case.
* The run function didn't have the universal_newlines parameter
documented
* The check_output function didn't have its text parameter documented
Even though Python marks any handles it opens as non-inheritable there
is still a race when using `subprocess.Popen` since creating a process
with redirected stdio requires temporarily creating inheritable handles.
By implementing support for `subprocess.Popen(close_fds=True)` we fix
this race.
In order to implement this we use PROC_THREAD_ATTRIBUTE_HANDLE_LIST
which is available since Windows Vista. Which allows to pass an explicit
list of handles to inherit when creating a process.
This commit also adds `STARTUPINFO.lpAttributeList["handle_list"]`
which can be used to control PROC_THREAD_ATTRIBUTE_HANDLE_LIST
directly.
Alex Waygood
Gregory P. Smith
slateny
Inada Naoki
Kumar Aditya
DonnaDia
Anthony Shaw
Jack DeVries
uniocto
andrei kulakov
Andre Delfino
sblondon
Ammar Askar
Paul Moore
Ruben Vorderman
Gareth Rees
Mathieu Dupuy
Zackery Spytz
Tim D. Smith
Victor Stinner
Jules Lasne (jlasne)
Patrick McLean
Tim Hoffmann
Christian Heimes
David Jones
Steve Dower
Serhiy Storchaka
Victor Stinner
Jules Lasne (jlasne)
Harmandeep Singh
Jakub Stasiak
Cheryl Sabella
Xiang Zhang
Andriy Maletsky
Sergey Fedoseev
Tobias Kunze
Pablo Galindo
Brice Gros
Anders Lorentsen
Bo Bayles
Segev Finer