@AlexWaygood I am really into tpyos, thanks! :)

Yuo're wellcom!

"received malformed or improperly-truncated ancillary data" message comes from Python if get_cmsg_data_len() returns non-zero. Can you please check in which case your are?

staticintget_cmsg_data_len(structmsghdr*msg,structcmsghdr*cmsgh,size_t*data_len){size_tspace,cmsg_data_len;if (!cmsg_min_space(msg,cmsgh,CMSG_LEN(0))||cmsgh->cmsg_len<CMSG_LEN(0))return-1;cmsg_data_len=cmsgh->cmsg_len-CMSG_LEN(0);if (!get_cmsg_data_space(msg,cmsgh,&space))return-1;if (space >=cmsg_data_len) {*data_len=cmsg_data_len;return0;    }*data_len=space;return1;}

Local debug shows that I face

printf("3");*data_len=space;return1;

Hm, I agree that this does not look like a proper fix. There's something else going on inside, for some reason there's not enough space to write the data.

The code was added in 2011 (bpo-6560,#50809,96fe56a). It does not emit a warning on Linux (at least I never see it). Were the warnings always on Windows, or did they appear in some version? Are they always expected in these tests, do they signal a problem? Shouldn't these tests fail if there was not a warning on Windows?

We should ask@ncoghlan for help, I guess :)

@sobolevn Could you test whether warnings were present in old Python versions (it was 3.2 or 3.3 I guess). Since most core developers do not use Windows, it might just slip past their notice.

I cannot build anything below 3.7 on mac sonora (m2) :(

3.7:

~/Desktop/cpython2  0f56adb8d7 ✗                                                          » ./python.exe -m test test_socket                         0:00:00 load avg: 5.09 Run tests sequentially0:00:00 load avg: 5.09 [1/1] test_socket/Users/sobolev/Desktop/cpython2/Lib/test/test_socket.py:2323: RuntimeWarning: received malformed or improperly-truncated ancillary data  result = sock.recvmsg(bufsize, *args)/Users/sobolev/Desktop/cpython2/Lib/test/test_socket.py:2414: RuntimeWarning: received malformed or improperly-truncated ancillary data  result = sock.recvmsg_into([buf], *args)== Tests result: SUCCESS ==1 test OK.Total duration: 24.0 secTests result: SUCCESS

3.8:

~/Desktop/cpython2  3.8 ✔                                                                 » ./python.exe -m test test_socket                         0:00:00 load avg: 6.11 Run tests sequentially0:00:00 load avg: 6.11 [1/1] test_socket/Users/sobolev/Desktop/cpython2/Lib/test/test_socket.py:2438: RuntimeWarning: received malformed or improperly-truncated ancillary data  result = sock.recvmsg(bufsize, *args)/Users/sobolev/Desktop/cpython2/Lib/test/test_socket.py:2529: RuntimeWarning: received malformed or improperly-truncated ancillary data  result = sock.recvmsg_into([buf], *args)== Tests result: SUCCESS ==1 test OK.Total duration: 23.2 secTests result: SUCCESS

So, this is not new at least.

@serhiy-storchaka:@sobolevn is trying to make warnings quiet on macOS, not on Windows. I don't know if these warnings are emitted on other platforms than macOS.

python -We -m test test_socket passes for me on Windows on a reasonably fresh build of Python 3.13, FWIW

@vstinner they appear both on Win and Mac, see my first commit:

• ubuntu (failing):https://github.com/python/cpython/actions/runs/6335548712/job/17206922402
• windows passing:https://github.com/python/cpython/actions/runs/6335548712/job/17206922528

@vstinner they appear both on Win and Mac, see my first commit

Oh ok.

@AlexWaygood@serhiy-storchaka@vstinner Any further comments on this PR?

I do not think that simply suppressing warnings here is the right solution. What is the warning about? What is the end user supposed to do with it? Non-zero result ofget_cmsg_data_len() should be either an error or ignored (note that there are two non-zero returned values). If such situation is common, then perhaps the code just does not handle all cases correctly.

What we can do is set the warning filter to default for these warnings, add a TODO comment and not close this issue

@AlexWaygood@serhiy-storchaka@vstinner Any further comments on this PR?

I only ever suggested some typo fixes on this one; it's well out of my area of expertise :-)

What we can do is set the warning filter to default for these warnings, add a TODO comment and not close this issue

I've now done this in the warnings as errors PR