With thePEP 475, the BEGIN_SELECT_LOOP and END_SELECT_LOOP macros ofModules/socketmodule.c became complex. Moreover, they are misused to handle EINTR. Most functions currently reimplemented their own loop inside the existing "select loop", and so the timeout is not recomputed correctly.Attached patch replaces the two macros with a new sock_call() function which takes a function as a parameter. IMO, the new code (sock_xxx_impl functions) is simpler to read, understand and debug.I hate debugging code (especially in gdb) using complex macros.Copy of sock_call() documentation:/* Call a socket function.   If the socket has a timeout, wait until the socket is ready before calling   the function: wait until the socket is writable if writing is nonzero, wait   until the socket received data otherwise.   If the function is interrupted by a signal (failed with EINTR): retry the   function, except if the signal handler raised an exception (PEP 475).   When the function is retried, recompute the timeout using a monotonic clock.   Raise an exception and return -1 on error, return 0 on success. */I was surprised by the number of lines of code. It probably means that we are solving a non trivial problem: calling correctly socket functions with a timeout and retrying when interrupted by a signal.

By the way, socket.sendto() has a bug: it stores the result of sendto() into a C int. It must store the result into a Py_ssize_t.  sock_call.patch already contains a fix for this.Attached sendto_ssizet.patch is the fix for Python 2.7 and 3.4.UDP packets cannot be larger than an ethernet frame which is smaller than 10,000 bytes. That's probabyl why nobody complained before. sendto() is only used for UDP, no?

I chose to not modify yet socket.sendall(). I prefer to wait until this patch is merged to rework this method. Currently, this method never recomputes the timeout.

sock_call-2.patch: add an inner looop in sock_call() to only retry func() when func() is interrupted by a signal. Limit also changes: try to only modify ctx around to call to sock_call(), move back some variables to the parent function. Rename the variable storing the result to "result". Add some more comments in sock_call().

New changeset358a2bcd0d0b by Victor Stinner in branch 'default':Issue#23834: Add sock_call() helper functionhttps://hg.python.org/cpython/rev/358a2bcd0d0b

New changesetb3c7ae99b8e0 by Victor Stinner in branch 'default':Issue#23834: Modify socket.sendall() to reuse sock_call() withhttps://hg.python.org/cpython/rev/b3c7ae99b8e0

Snow Leopard doesn't like me (or the opposite?), the changeset358a2bcd0d0b introduced a regression. I'm unable to reproduce, I ran test_socket on Linux (3.18), Mac OS X (Yosemite, Mac OS X 10.10) and FreeBSD (10).I don't see a significant difference in sock_sendmsg()http://buildbot.python.org/all/builders/AMD64%20Snow%20Leop%203.x/builds/2896/steps/test/logs/stdio======================================================================ERROR: testSendmsgTimeout (test.test_socket.SendmsgTCPTest)----------------------------------------------------------------------Traceback (most recent call last):  File "/Users/buildbot/buildarea/3.x.murray-snowleopard/build/Lib/test/test_socket.py", line 266, in _tearDown    raise exc  File "/Users/buildbot/buildarea/3.x.murray-snowleopard/build/Lib/test/test_socket.py", line 278, in clientRun    test_func()  File "/Users/buildbot/buildarea/3.x.murray-snowleopard/build/Lib/test/test_socket.py", line 2224, in _testSendmsgTimeout    self.sendmsgToServer([b"a"*512])  File "/Users/buildbot/buildarea/3.x.murray-snowleopard/build/Lib/test/test_socket.py", line 1913, in sendmsgToServer    *(args + self.sendmsg_to_server_defaults[len(args):]))BrokenPipeError: [Errno 32] Broken pipe======================================================================FAIL: testSendmsgTimeout (test.test_socket.SendmsgTCPTest)----------------------------------------------------------------------Traceback (most recent call last):  File "/Users/buildbot/buildarea/3.x.murray-snowleopard/build/Lib/test/test_socket.py", line 2217, in testSendmsgTimeout    self.assertTrue(self.misc_event.wait(timeout=self.fail_timeout))AssertionError: False is not true

New changeset920b700d9509 by Victor Stinner in branch 'default':Issue#23834: Fix sock_call(), set deadline_initialized to recompute the timeouthttps://hg.python.org/cpython/rev/920b700d9509

The changeset920b700d9509 fixed AMD64 Snow Leop 3.x, I close the issue.

New changeset29c32ca46652 by Victor Stinner in branch '2.7':Issue#23834: Fix socket.sendto(), use the C long type to store the result ofhttps://hg.python.org/cpython/rev/29c32ca46652New changeset436bb7ad6349 by Victor Stinner in branch '3.4':Issue#23834: Fix socket.sendto(), use the C Py_ssize_t type to store thehttps://hg.python.org/cpython/rev/436bb7ad6349New changeseta064abfd436c by Victor Stinner in branch 'default':(Merge 3.4) Issue#23834: Fix socket.sendto(), use the C Py_ssize_t type tohttps://hg.python.org/cpython/rev/a064abfd436c

New changeset7a9c49885cd3 by Victor Stinner in branch 'default':Issue#23834: Simplify timeout handlinghttps://hg.python.org/cpython/rev/7a9c49885cd3

New changeset7f54676348d3 by Victor Stinner in branch 'default':Issue#23834: Fix initial value of the socket timeouthttps://hg.python.org/cpython/rev/7f54676348d3

New changeset462680f4e8af by Victor Stinner in branch 'default':Issue#23834: Fix the default socket timeouthttps://hg.python.org/cpython/rev/462680f4e8af

New changesetcd60eccaa331 by Victor Stinner in branch '3.5':Issue#24732,#23834: Fix sock_accept_impl() on Windowshttps://hg.python.org/cpython/rev/cd60eccaa331