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On Mac OS 10.7, test_faulthandler fails. See test output below.
It looks as though the tests may be at fault in expecting to see "(?:Segmentation fault|Bus error)" instead of "(?:Segmentation fault|Bus error|Illegal instruction)".
 test_disable (__main__.FaultHandlerTests) ... ok
 test_dump_traceback (__main__.FaultHandlerTests) ... ok
 test_dump_traceback_file (__main__.FaultHandlerTests) ... ok
 test_dump_traceback_threads (__main__.FaultHandlerTests) ... ok
 test_dump_traceback_threads_file (__main__.FaultHandlerTests) ... ok
 test_dump_tracebacks_later (__main__.FaultHandlerTests) ... ok
 test_dump_tracebacks_later_cancel (__main__.FaultHandlerTests) ... ok
 test_dump_tracebacks_later_file (__main__.FaultHandlerTests) ... ok
 test_dump_tracebacks_later_repeat (__main__.FaultHandlerTests) ... ok
 test_dump_tracebacks_later_twice (__main__.FaultHandlerTests) ... ok
 test_enable_file (__main__.FaultHandlerTests) ... FAIL
 test_enable_single_thread (__main__.FaultHandlerTests) ... FAIL
 test_fatal_error (__main__.FaultHandlerTests) ... ok
 test_gil_released (__main__.FaultHandlerTests) ... FAIL
 test_is_enabled (__main__.FaultHandlerTests) ... ok
 test_read_null (__main__.FaultHandlerTests) ... FAIL
 test_register (__main__.FaultHandlerTests) ... ok
 test_register_chain (__main__.FaultHandlerTests) ... ok
 test_register_file (__main__.FaultHandlerTests) ... ok
 test_register_threads (__main__.FaultHandlerTests) ... ok
 test_sigabrt (__main__.FaultHandlerTests) ... ok
 test_sigbus (__main__.FaultHandlerTests) ... ok
 test_sigfpe (__main__.FaultHandlerTests) ... ok
 test_sigill (__main__.FaultHandlerTests) ... ok
 test_sigsegv (__main__.FaultHandlerTests) ... ok
 test_stack_overflow (__main__.FaultHandlerTests) ... ok
 test_unregister (__main__.FaultHandlerTests) ... ok
 ======================================================================
 FAIL: test_enable_file (__main__.FaultHandlerTests)
 ----------------------------------------------------------------------
 Traceback (most recent call last):
 File "test_faulthandler.py", line 207, in test_enable_file
 filename=filename)
 File "test_faulthandler.py", line 105, in check_fatal_error
 self.assertRegex(output, regex)
 AssertionError: Regex didn't match: '^Fatal Python error: (?:Segmentation fault|Bus error)\n\nCurrent\\ thread\\ XXX:\n File "<string>", line 4 in <module>$' not found in 'Fatal Python error: Illegal instruction\n\nCurrent thread XXX:\n File "<string>", line 4 in <module>'
 ======================================================================
 FAIL: test_enable_single_thread (__main__.FaultHandlerTests)
 ----------------------------------------------------------------------
 Traceback (most recent call last):
 File "test_faulthandler.py", line 217, in test_enable_single_thread
 all_threads=False)
 File "test_faulthandler.py", line 105, in check_fatal_error
 self.assertRegex(output, regex)
 AssertionError: Regex didn't match: '^Fatal Python error: (?:Segmentation fault|Bus error)\n\nTraceback\\ \\(most\\ recent\\ call\\ first\\):\n File "<string>", line 3 in <module>$' not found in 'Fatal Python error: Illegal instruction\n\nTraceback (most recent call first):\n File "<string>", line 3 in <module>'
 ======================================================================
 FAIL: test_gil_released (__main__.FaultHandlerTests)
 ----------------------------------------------------------------------
 Traceback (most recent call last):
 File "test_faulthandler.py", line 195, in test_gil_released
 '(?:Segmentation fault|Bus error)')
 File "test_faulthandler.py", line 105, in check_fatal_error
 self.assertRegex(output, regex)
 AssertionError: Regex didn't match: '^Fatal Python error: (?:Segmentation fault|Bus error)\n\nCurrent\\ thread\\ XXX:\n File "<string>", line 3 in <module>$' not found in 'Fatal Python error: Illegal instruction\n\nCurrent thread XXX:\n File "<string>", line 3 in <module>'
 ======================================================================
 FAIL: test_read_null (__main__.FaultHandlerTests)
 ----------------------------------------------------------------------
 Traceback (most recent call last):
 File "test_faulthandler.py", line 115, in test_read_null
 '(?:Segmentation fault|Bus error)')
 File "test_faulthandler.py", line 105, in check_fatal_error
 self.assertRegex(output, regex)
 AssertionError: Regex didn't match: '^Fatal Python error: (?:Segmentation fault|Bus error)\n\nCurrent\\ thread\\ XXX:\n File "<string>", line 3 in <module>$' not found in 'Fatal Python error: Illegal instruction\n\nCurrent thread XXX:\n File "<string>", line 3 in <module>'
 ----------------------------------------------------------------------
 Ran 27 tests in 21.711s
 FAILED (failures=4)
 Traceback (most recent call last):
 File "test_faulthandler.py", line 550, in <module>
 test_main()
 File "test_faulthandler.py", line 547, in test_main
 support.run_unittest(FaultHandlerTests)
 File "/Users/gdr/hg.python.org/cpython/Lib/test/support.py", line 1327, in run_unittest
 _run_suite(suite)
 File "/Users/gdr/hg.python.org/cpython/Lib/test/support.py", line 1302, in _run_suite
 raise TestFailed(err)
 test.support.TestFailed: multiple errors occurred

test_enable_file, test_enable_single_thread, test_gil_released and test_read_null read an int (4 bytes) from the address 0 (NULL).
test_sigsegv pass: this test raises explicitly a SIGSEGV and the signal handler writes the right message ("Segmentation fault").
Mac OS X Lion raises maybe a SIGILL on a segmentation fault if the address is zero? I suppose that it raises a SIGSEGV if the address is not zero.
Can you try to modify the function faulthandler_read_null() in Modules/faulthandler.c: replace "int *x = NULL, y;" by "int *x = (int *)1, y;" ? Then recompile (make) and rerun the test (./python.exe -m test -v test_faulthandler).

After changing NULL to (int *)1, all tests pass.

New changeset 1777df2ce50d by Victor Stinner in branch 'default':
Issue #12700: fix test_faulthandler for Mac OS X Lion
http://hg.python.org/cpython/rev/1777df2ce50d 

> After changing NULL to (int *)1, all tests pass.
Ok, so Lion has a special case for reading from NULL. I changed the tests to try to fix your bug. Can you tell me if it's now better?

All tests now pass.

> All tests now pass.
Ok, thanks for your report and your feedback.