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overflow_check_* failures in tests #3588

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gsnedders opened this issue May 8, 2020 · 0 comments · Fixed by #3591
Closed

overflow_check_* failures in tests #3588

gsnedders opened this issue May 8, 2020 · 0 comments · Fixed by #3591
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Code Generation defect
Milestone
3.0

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@gsnedders
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gsnedders commented May 8, 2020 •
edited

Running the tests with CC=-ftrapv shows that #1911 isn't the only overflow-related error and we're thus hitting undefined behaviour in other cases; notably in Overflow.c we often do operations on signed integers regardless of whether or not we're in the overflow case. PR forthcoming.

cython$ CFLAGS=-ftrapv python runtests.py overflow
Python 3.8.2 (default, Apr  8 2020, 14:31:25) 
[GCC 9.3.0]

Running tests against Cython 3.0a4 3bba77a2bf9ed7da4c118fd7887658c597e14cd2
Using Cython language level 2.
Backends: c,cpp

Fatal Python error: Aborted

Thread 0x00007fb5bcdce700 (most recent call first):
  File "runtests.py", line 2267 in time_stamper
  File "/usr/lib/python3.8/threading.py", line 870 in run
  File "/usr/lib/python3.8/threading.py", line 932 in _bootstrap_inner
  File "/usr/lib/python3.8/threading.py", line 890 in _bootstrap

Current thread 0x00007fb5bdda3740 (most recent call first):
  File "<doctest overflow_check_int.test_add_const[1]>", line 1 in <module>
  File "/usr/lib/python3.8/doctest.py", line 1329 in __run
  File "/usr/lib/python3.8/doctest.py", line 1476 in run
  File "/usr/lib/python3.8/doctest.py", line 2191 in runTest
  File "/usr/lib/python3.8/unittest/case.py", line 633 in _callTestMethod
  File "/usr/lib/python3.8/unittest/case.py", line 676 in run
  File "/usr/lib/python3.8/unittest/case.py", line 736 in __call__
  File "/usr/lib/python3.8/unittest/suite.py", line 122 in run
  File "runtests.py", line 1315 in run_test
  File "runtests.py", line 1321 in run_forked_test
  File "runtests.py", line 1316 in run_doctests
  File "runtests.py", line 1304 in run_tests
  File "runtests.py", line 1286 in run
  File "/usr/lib/python3.8/unittest/case.py", line 736 in __call__
  File "/usr/lib/python3.8/unittest/suite.py", line 122 in run
  File "/usr/lib/python3.8/unittest/suite.py", line 84 in __call__
  File "/usr/lib/python3.8/unittest/suite.py", line 122 in run
  File "/usr/lib/python3.8/unittest/suite.py", line 84 in __call__
  File "/usr/lib/python3.8/unittest/suite.py", line 122 in run
  File "/usr/lib/python3.8/unittest/suite.py", line 84 in __call__
  File "/usr/lib/python3.8/unittest/runner.py", line 176 in run
  File "runtests.py", line 2573 in runtests
  File "runtests.py", line 2209 in main
  File "runtests.py", line 2595 in <module>
Aborted (core dumped)
@gsnedders gsnedders changed the title Overflow failures in tests overflow_check_* failures in tests May 8, 2020
gsnedders added a commit to gsnedders/cython that referenced this issue May 8, 2020
@gsnedders
Fix cython#3588: Make existing overflow code safe
7d9a545 
Signed overflow is undefined behaviour in C and compilers can and do
optimized on that basis.
gsnedders added a commit to gsnedders/cython that referenced this issue May 8, 2020
@gsnedders
Fix cython#3588: Make existing overflow code safe
4db5901 
Signed overflow is undefined behaviour in C and compilers can and do
optimized on that basis.
@gsnedders gsnedders mentioned this issue May 8, 2020
Merged
@scoder scoder added this to the 3.0 milestone May 18, 2020
scoder pushed a commit that referenced this issue May 18, 2020
@gsnedders
Fix several issues in overflow checks (GH-3591)
92a0b75 
* Fix #3588: Make existing overflow code safe

Signed overflow is undefined behaviour in C and compilers can and do optimized on that basis.

* Speed up our overflow impls

Note this is primarily based on performance of compilers which do not
support __builtin_add_overflow (i.e., not Clang >= 3.4 & gcc >= 5),
mostly looking at several gcc 4 releases (used by older, supported,
RHEL releases and Debian 8 "Jessie") and MSVC.

* Use __builtin_XXX_overflow if available

This is much quicker in general, as these all just then read the overflow flag from the status register.
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Fix overflow_check gsnedders/cython
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