GH-134453: Fix subprocess memoryview input handling on POSIX

[gpshead]

Fix inconsistent subprocess.Popen.communicate() behavior between Windows and POSIX when using memoryview objects with non-byte elements as input.

On POSIX systems, the code was incorrectly comparing bytes written against element count instead of byte count, causing data truncation for large inputs with non-byte element types.

Changes:

• Cast memoryview inputs to byte view when input is already a memoryview
• Fix progress tracking to use len(input_view) instead of len(self._input)
• Added tests for memoryview inputs

• Issue: Inconsistent subprocess.Popen.communicate() behavior between Windows and Posix on non-byte memoryview input #134453

[miss-islington-app]

Thanks @gpshead for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-142062 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-142063 is a backport of this pull request to the 3.13 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 FreeBSD Refleaks 3.14 (tier-3) has failed when building commit c1d3e25.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1800/builds/743) and take a look at the build logs.
4. Check if the failure is related to this commit (c1d3e25) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1800/builds/743

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/buildbot/buildarea/3.14.ware-freebsd.refleak/build/Lib/test/support/__init__.py", line 847, in gc_collect
    gc.collect()
ResourceWarning: unclosed <socket.socket fd=9, family=2, type=1, proto=6, laddr=('127.0.0.1', 63223), raddr=('127.0.0.1', 63224)>
Task was destroyed but it is pending!
task: <Task pending name='Task-2667' coro=<BaseSelectorEventLoop._accept_connection2() done, defined at /buildbot/buildarea/3.14.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py:217> wait_for=<Future pending cb=[Task.task_wakeup()]>>
Warning -- Unraisable exception
Exception ignored while calling deallocator <function _SelectorTransport.__del__ at 0x8467cbd10>:
Traceback (most recent call last):
  File "/buildbot/buildarea/3.14.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py", line 873, in __del__
    _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
ResourceWarning: unclosed transport <_SelectorSocketTransport closing fd=9>
k


Traceback (most recent call last):
  File "/buildbot/buildarea/3.14.ware-freebsd.refleak/build/Lib/test/support/__init__.py", line 847, in gc_collect
    gc.collect()
ResourceWarning: unclosed <socket.socket fd=9, family=2, type=1, proto=6, laddr=('127.0.0.1', 12223), raddr=('127.0.0.1', 12224)>
Task was destroyed but it is pending!
task: <Task pending name='Task-320' coro=<BaseSelectorEventLoop._accept_connection2() done, defined at /buildbot/buildarea/3.14.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py:217> wait_for=<Future pending cb=[Task.task_wakeup()]>>
Warning -- Unraisable exception
Exception ignored while calling deallocator <function _SelectorTransport.__del__ at 0x843167d10>:
Traceback (most recent call last):
  File "/buildbot/buildarea/3.14.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py", line 873, in __del__
    _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
ResourceWarning: unclosed transport <_SelectorSocketTransport closing fd=9>
k