`test_socket` generates several warnings

[sobolevn]

Bug report

Repro: ./python.exe -We -m test test_socket -v

======================================================================
ERROR: testSecondCmsgTruncInData (test.test_socket.RecvmsgIntoRFC3542AncillaryUDP6Test.testSecondCmsgTruncInData)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 4324, in testSecondCmsgTruncInData
    msg, ancdata, flags, addr = self.doRecvmsg(
                                ^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2940, in doRecvmsg
    result = sock.recvmsg_into([buf], *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testSingleCmsgTruncInData (test.test_socket.RecvmsgIntoRFC3542AncillaryUDP6Test.testSingleCmsgTruncInData)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 4220, in testSingleCmsgTruncInData
    msg, ancdata, flags, addr = self.doRecvmsg(
                                ^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2940, in doRecvmsg
    result = sock.recvmsg_into([buf], *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testCmsgTruncLen0 (test.test_socket.RecvmsgIntoSCMRightsStreamTest.testCmsgTruncLen0)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3897, in testCmsgTruncLen0
    self.checkTruncatedArray(ancbuf=socket.CMSG_LEN(0), maxdata=0)
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3877, in checkTruncatedArray
    msg, ancdata, flags, addr = self.doRecvmsg(self.serv_sock,
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2940, in doRecvmsg
    result = sock.recvmsg_into([buf], *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testCmsgTruncLen0Plus1 (test.test_socket.RecvmsgIntoSCMRightsStreamTest.testCmsgTruncLen0Plus1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3903, in testCmsgTruncLen0Plus1
    self.checkTruncatedArray(ancbuf=socket.CMSG_LEN(0) + 1, maxdata=1)
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3877, in checkTruncatedArray
    msg, ancdata, flags, addr = self.doRecvmsg(self.serv_sock,
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2940, in doRecvmsg
    result = sock.recvmsg_into([buf], *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testCmsgTruncLen1 (test.test_socket.RecvmsgIntoSCMRightsStreamTest.testCmsgTruncLen1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3909, in testCmsgTruncLen1
    self.checkTruncatedArray(ancbuf=socket.CMSG_LEN(SIZEOF_INT),
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3877, in checkTruncatedArray
    msg, ancdata, flags, addr = self.doRecvmsg(self.serv_sock,
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2940, in doRecvmsg
    result = sock.recvmsg_into([buf], *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testCmsgTruncLen2Minus1 (test.test_socket.RecvmsgIntoSCMRightsStreamTest.testCmsgTruncLen2Minus1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3916, in testCmsgTruncLen2Minus1
    self.checkTruncatedArray(ancbuf=socket.CMSG_LEN(2 * SIZEOF_INT) - 1,
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3877, in checkTruncatedArray
    msg, ancdata, flags, addr = self.doRecvmsg(self.serv_sock,
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2940, in doRecvmsg
    result = sock.recvmsg_into([buf], *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testSecondCmsgTruncInData (test.test_socket.RecvmsgRFC3542AncillaryUDP6Test.testSecondCmsgTruncInData)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 4324, in testSecondCmsgTruncInData
    msg, ancdata, flags, addr = self.doRecvmsg(
                                ^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2849, in doRecvmsg
    result = sock.recvmsg(bufsize, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testSingleCmsgTruncInData (test.test_socket.RecvmsgRFC3542AncillaryUDP6Test.testSingleCmsgTruncInData)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 4220, in testSingleCmsgTruncInData
    msg, ancdata, flags, addr = self.doRecvmsg(
                                ^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2849, in doRecvmsg
    result = sock.recvmsg(bufsize, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testCmsgTruncLen0 (test.test_socket.RecvmsgSCMRightsStreamTest.testCmsgTruncLen0)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3897, in testCmsgTruncLen0
    self.checkTruncatedArray(ancbuf=socket.CMSG_LEN(0), maxdata=0)
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3877, in checkTruncatedArray
    msg, ancdata, flags, addr = self.doRecvmsg(self.serv_sock,
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2849, in doRecvmsg
    result = sock.recvmsg(bufsize, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testCmsgTruncLen0Plus1 (test.test_socket.RecvmsgSCMRightsStreamTest.testCmsgTruncLen0Plus1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3903, in testCmsgTruncLen0Plus1
    self.checkTruncatedArray(ancbuf=socket.CMSG_LEN(0) + 1, maxdata=1)
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3877, in checkTruncatedArray
    msg, ancdata, flags, addr = self.doRecvmsg(self.serv_sock,
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2849, in doRecvmsg
    result = sock.recvmsg(bufsize, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testCmsgTruncLen1 (test.test_socket.RecvmsgSCMRightsStreamTest.testCmsgTruncLen1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3909, in testCmsgTruncLen1
    self.checkTruncatedArray(ancbuf=socket.CMSG_LEN(SIZEOF_INT),
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3877, in checkTruncatedArray
    msg, ancdata, flags, addr = self.doRecvmsg(self.serv_sock,
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2849, in doRecvmsg
    result = sock.recvmsg(bufsize, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

======================================================================
ERROR: testCmsgTruncLen2Minus1 (test.test_socket.RecvmsgSCMRightsStreamTest.testCmsgTruncLen2Minus1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3916, in testCmsgTruncLen2Minus1
    self.checkTruncatedArray(ancbuf=socket.CMSG_LEN(2 * SIZEOF_INT) - 1,
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 3877, in checkTruncatedArray
    msg, ancdata, flags, addr = self.doRecvmsg(self.serv_sock,
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_socket.py", line 2849, in doRecvmsg
    result = sock.recvmsg(bufsize, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeWarning: received malformed or improperly-truncated ancillary data

----------------------------------------------------------------------
Ran 483 tests in 27.924s

FAILED (errors=12, skipped=245)
test test_socket failed
test_socket failed (12 errors)

== Tests result: FAILURE ==

1 test failed:
    test_socket

Total duration: 28.0 sec
Total tests: run=483 skipped=245
Total test files: run=1/1 failed=1
Result: FAILURE

I have a fix ready.

Linked PRs

• gh-110012: Fix RuntimeWarning in test_socket #110013
• gh-128770: fix ResourceWarning in test_pyrepl #128906

[serhiy-storchaka]

These three methods that potentially emit a warning generate 18 tests in total.

$ ./python -m test test_socket --list-cases -m testSingleCmsgTruncInData -m testSecondCmsgTruncInData -m 'testCmsgTruncLen*'
test.test_socket.RecvmsgIntoRFC3542AncillaryUDP6Test.testSecondCmsgTruncInData
test.test_socket.RecvmsgIntoRFC3542AncillaryUDP6Test.testSingleCmsgTruncInData
test.test_socket.RecvmsgIntoRFC3542AncillaryUDPLITE6Test.testSecondCmsgTruncInData
test.test_socket.RecvmsgIntoRFC3542AncillaryUDPLITE6Test.testSingleCmsgTruncInData
test.test_socket.RecvmsgIntoSCMRightsStreamTest.testCmsgTruncLen0
test.test_socket.RecvmsgIntoSCMRightsStreamTest.testCmsgTruncLen0Minus1
test.test_socket.RecvmsgIntoSCMRightsStreamTest.testCmsgTruncLen0Plus1
test.test_socket.RecvmsgIntoSCMRightsStreamTest.testCmsgTruncLen1
test.test_socket.RecvmsgIntoSCMRightsStreamTest.testCmsgTruncLen2Minus1
test.test_socket.RecvmsgRFC3542AncillaryUDP6Test.testSecondCmsgTruncInData
test.test_socket.RecvmsgRFC3542AncillaryUDP6Test.testSingleCmsgTruncInData
test.test_socket.RecvmsgRFC3542AncillaryUDPLITE6Test.testSecondCmsgTruncInData
test.test_socket.RecvmsgRFC3542AncillaryUDPLITE6Test.testSingleCmsgTruncInData
test.test_socket.RecvmsgSCMRightsStreamTest.testCmsgTruncLen0
test.test_socket.RecvmsgSCMRightsStreamTest.testCmsgTruncLen0Minus1
test.test_socket.RecvmsgSCMRightsStreamTest.testCmsgTruncLen0Plus1
test.test_socket.RecvmsgSCMRightsStreamTest.testCmsgTruncLen1
test.test_socket.RecvmsgSCMRightsStreamTest.testCmsgTruncLen2Minus1

But only 12 of them are failed above. Are they always the same tests? What is the difference between tests that passed and tests that failed? Or was they skipped? Try to run only these test (-m testSingleCmsgTruncInData -m testSecondCmsgTruncInData -m 'testCmsgTruncLen*').

[sobolevn]

Only two warnings are left:

» ./python.exe -m test test_socket
Using random seed: 2077083042
0:00:00 load avg: 1.67 Run 1 test sequentially in a single process
0:00:00 load avg: 1.67 [1/1] test_socket
/Users/sobolev/Desktop/cpython2/Lib/test/test_socket.py:2999: RuntimeWarning: received malformed or improperly-truncated ancillary data
  result = sock.recvmsg_into([buf], *args)
/Users/sobolev/Desktop/cpython2/Lib/test/test_socket.py:2908: RuntimeWarning: received malformed or improperly-truncated ancillary data
  result = sock.recvmsg(bufsize, *args)

== Tests result: SUCCESS ==

1 test OK.

Total duration: 27.2 sec
Total tests: run=733 skipped=246
Total test files: run=1/1
Result: SUCCESS